# Downsides to downsizing canister tubing?



## OVT (Nov 29, 2011)

I have an Eheim 2026 driving a 2'-long 17g 60P.
I am considering downsizing the tubing from 5/8" to 1/2" by using reducing barbs, mostly so that I can use smaller pipes.
The filter has adjustable flow control.

Am I overlooking any issues? Thanks!


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## tobystanton (Jun 27, 2012)

Make sure you have metal clamp's securely tightened on both sides of the reducing barb, mine weren't tightened 100% and I woke up with the water level at 50% = (


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## DogFish (Jul 16, 2011)

Downsides to downsizing canister tubing?

You'll add resistance to the pump by decreasing the inside diameter of the exhaust hose. That will increase water speed out a bit and make the pump work a bit harder to push the water.

Since your filter has a flow adjustment I doubt this will matter to the life of your pump.


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## proaudio55 (Oct 20, 2011)

Smaller pipes (and elbows) mean more friction to the fluid passing through. More friction means slower and less flow...

If you are already having to throttle-down your filter's flow, then smaller tubing shouldn't be an issue. However, if you are struggling to get enough flow: reducing your tubing size will exacerbate the problem.


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## accordztech (Dec 6, 2004)

I think if you are reducing the tubing size, then only reduce the outlet and not the inlet size. If you reduce the inlet size then your pump may suffer.

But why do you want to downsize? Just for the use of smaller tubing? I dont get it.


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## Jmlampert23 (Jul 25, 2012)

the main problem is that the pump is going to work harder if you reduce the internal diameter of the tubing. This could make it die on you prematurely. It will also cause the water to come out the end of the tubing stronger which can cause more water flow in the tank than you need or want


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## PlantedRich (Jul 21, 2010)

I'm missing something when folks talk about harm to the motor. Can somebody explain how this can happen? What parts of the motor are harmed? I know there is a lot of concern out there but i would like to see some specific information.


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## Jmlampert23 (Jul 25, 2012)

the pump is made to pump a certain amount of water through the tubing. if the tubing size is reduced the pump will still try to push that same amount of water through the smaller tubing causing strain on the pump motor.


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## AndreyT (Apr 28, 2011)

Jmlampert23 said:


> the pump is made to pump a certain amount of water through the tubing. if the tubing size is reduced the pump will still try to push that same amount of water through the smaller tubing causing strain on the pump motor.


Well, it should be noted that this logic mostly applies to positive displacement pumps. 

A typical canister filters uses impeller pump. Impeller pump is not a positive displacement pump. Even if you completely block the return tube, the impeller will still continue to uselessly churn water inside the filter. This might increase the pump load, but not by much.

In a canister filter the pump does not have to make any work in order to lift the water back into the tank, since the water essentially lifts itself. The only real work the pump has to do in a canister filter is to push the water through the media. For this reason, canister filters are typically very insensitive to the intake and return tube parameters. Changing the tube diameter might indeed affect the flow speed to some degree, but the change in the pump load will be insignificant.


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## OVT (Nov 29, 2011)

Roger on the clamps and reduced flow. Any other concerns?

Motor-wise, *AndreyT* is correct.

All canister filters that I know off (and Koralias etc) have a single moving part - the impeller. The impeller is a cylinder with magnetic core with a ceramic shaft through it and has blades attached. The impeller rotates around the shaft with the blades moving the water. The impeller is surrounded by an alternating magnetic field that makes the impeller spin.

The flow control on all Eheims is accomplished by mechanically adjusting intake and outflow tubing opening's area, a la ball valves.


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## proaudio55 (Oct 20, 2011)

PlantedRich said:


> I'm missing something when folks talk about harm to the motor. Can somebody explain how this can happen? What parts of the motor are harmed? I know there is a lot of concern out there but i would like to see some specific information.


In the world of industrial boilers, if you throttle a centrifugal pump by valving the intake... very bad things happen! The pump will start to cavitate: The spinning impeller will literally boil the water. The bubbles that form inside the volute (snail-shell shaped pump housing) will absolutely destroy the pump's impeller blades. 

If you need to throttle a centrifugal pump, always close down the valve on the outlet. That will reduce the flow output, reduce the electrical draw to the motor, and won't do any damage.

I know a little canister filter is different than a 500PSI feed water pump, but both are centrifugal pumps and working on same basic physics.


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## PlantedRich (Jul 21, 2010)

But the whole point of the discussion is based on a totally different system. There are no parts in a mag drive pump which are strong enough to boil water. Many of them use less than 60 watts to run. What I find when I ask for clear answers on how a pump is strained is that people are not applying logic but just going on what they have learned about motors. Often it is based on a totally different type of motor. 

Without motor windings, bearings, brushes, and lubrication to break down, the idea that it will "strain" a mag drive is just using old logic on new equipment. One of the big reasons for mag drive motors is that they use very little electrical power and will not burn up even if the impeller totally stops. They do not burn up because there are no wires on the impeller to overheat and melt like a regular type motor might. Stopping the impeller does not increase nor decrease the current through the motor. There is no current through the impeller to change. It is only an electro- magnetic field which does not care what the impeller is doing. It also takes a lot more power to burn up a magnet. Far more than any canister filter uses. 

If you choose to use a boiler pump as a filter for your tank, you will likely have a number of problems. Like needing three phase power brought to your house?/


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## kevmo911 (Sep 24, 2010)

To possibly help picture what's going on (or not, but hey, it's more info), you're reducing the tubing to 64% of the original area. So the pump is trying to push the same amount of water through a hole that just got 36% smaller.


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## Aquaticfan (Oct 30, 2011)

AndreyT said:


> Well, it should be noted that this logic mostly applies to positive displacement pumps.
> 
> A typical canister filters uses impeller pump. Impeller pump is not a positive displacement pump. Even if you completely block the return tube, the impeller will still continue to uselessly churn water inside the filter. This might increase the pump load, but not by much.
> 
> In a canister filter the pump does not have to make any work in order to lift the water back into the tank, since the water essentially lifts itself. The only real work the pump has to do in a canister filter is to push the water through the media. For this reason, canister filters are typically very insensitive to the intake and return tube parameters. Changing the tube diameter might indeed affect the flow speed to some degree, but the change in the pump load will be insignificant.



This is correct........ 

As long as the intake flow and output flow match/ are equal or as long as the intake flow is greater then the output flow you wont have any issues with the impeller or the motor having cavitation or anything like that. No additional stress on the motor. 

Now..... your GPH will go down but your ability to run at a higher head pressure increases so at even a lower head pressure with reduced GPH your pressure output will be greater.


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## HD Blazingwolf (May 12, 2011)

so to simplify the blah blah blah

ur pump will not cavitate because head pressure will be equal to the back pressure of the intake
ur flow will decrease which i think is ur original goal and smaller glass pipes?


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## PlantedRich (Jul 21, 2010)

Now the true facts begin to come out! You will reduce the flow from the filter. There will be no damage done to the motor and you will have accomplished what you wanted. All the rest is just wasted theory! 

If it was going to ruin a filter to restrict flow, would a company with a rep like Ehiem send filters out without warning about restricting flow? Filters wouldn't last long if they burned out every time a leaf blocked the intake or the prefilter got dirty.


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## HD Blazingwolf (May 12, 2011)

blocking the intake can do damage. it takes a lot of restrictio though. they have design tolerances they can handle

u restrict the intake and head pressure stays the same but intake pressure or negative head pressure drops. this is how cavitation on positive displacement pumps happens

it can still happen to a cannister. the impeller causes the air dissolved in the water to come out of suspension. a cannister can probably tolerate 10% cavitation for its life cycle

you won't get this high though as we are working with very low pressures


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## GeToChKn (Apr 15, 2011)

All Eheim's and Fluvals that have adjustable flow, restrict the intake and outtake at the same time. Look at any of the double tap/hose connectors for either brand. You push the level, a ball-valve style ball closes the hole, thus reducing size and I don't think anyone has ever boiled water or blown up a filter or started a small nuclear chain reaction between anti-matter and matter just by turning down one of these filters running stock.


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## AndreyT (Apr 28, 2011)

PlantedRich said:


> Without motor windings, bearings, brushes, and lubrication to break down, the idea that it will "strain" a mag drive is just using old logic on new equipment. One of the big reasons for mag drive motors is that they use very little electrical power and will not burn up even if the impeller totally stops. They do not burn up because there are no wires on the impeller to overheat and melt like a regular type motor might. Stopping the impeller does not increase nor decrease the current through the motor. There is no current through the impeller to change. It is only an electro- magnetic field which does not care what the impeller is doing. It also takes a lot more power to burn up a magnet. Far more than any canister filter uses.


That's actually not accurate. 

What you can a "mag drive" is actually an permanent-magnet synchronous AC motor (what is also commonly known as _brushless_ electric motor in DC terminology). I don't want to turn this into a lecture on physics of brushless motors, but I's still like to note that the mechanical load level experienced by the rotor will immediately and strongly affect the amount of electric current that flows through the stator windings. It is not even remotely correct to say that "electro-magnetic field does not care what the impeller is doing". The configuration of that electro-magnetic field depends critically on what the rotor (impeller) is doing and that configuration will greatly affect the reactive resistance of the stator windings.

For these reasons, if you deliberately stall the rotor of the brushless motor (like block the impeller, for example), it will immediately result is significant rise of the current flowing through the motor and will eventually overheat it and burn it out.

Again, impeller pump in a canister filter is not a positive displacement pump. It is a relatively slow centrifugal pump. For that reason, it is fairly insensitive to any intake or return flow restrictions. It won't overheat and burn out just because of that. Restricting flows does not increase the load on the impeller that much. 

Nevertheless its is still incorrect to say that "mag drive motor does not care about the rotor (impeller) load". All electric motors exhibit very strong relationship between the load on the rotor shaft and the consumed power. It is actually one of the wonders of physics, how the Law of Energy Conservation finds a way to manifest itself consistently in electric motors of completely different design (as in brushed vs. brushless).


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## OVT (Nov 29, 2011)

GeToChKn said:


> All Eheim's and Fluvals that have adjustable flow, restrict the intake and outtake at the same time. Look at any of the double tap/hose connectors for either brand. You push the level, a ball-valve style ball closes the hole, thus reducing size and I don't think anyone has ever boiled water or blown up a filter or started a small nuclear chain reaction between anti-matter and matter just by turning down one of these filters running stock.


roud: Exactly, as I mentioned above. I was not worried about the load on mag-drive for that reason, but was checking to see if I;ve overlooked anything else.

Thanks a lot to all for the time and the comments. I think I have a project for this weekend


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## proaudio55 (Oct 20, 2011)

AndreyT said:


> That's actually not accurate.
> 
> What you can a "mag drive" is actually an permanent-magnet synchronous AC motor (what is also commonly known as _brushless_ electric motor in DC terminology). I don't want to turn this into a lecture on physics of brushless motors, but I's still like to note that the mechanical load level experienced by the rotor will immediately and strongly affect the amount of current that flows through the stator windings. It is not even remotely correct to say that "electro-magnetic field does not care what the impeller is doing". The configuration of that electro-magnetic field depends critically on what the rotor (impeller) is doing and that configuration will greatly affect the reactive resistance of the stator windings.
> 
> ...


OMG Nerdgasm!! :biggrin:


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## keithy (Jun 8, 2010)

I don't mean to jump into this discussion. But the whole thing can be simplified to two words. Back pressure. 
Restricting flow is also equivalent to a valve partially open. Therefore, back pressure increases. Back pressure cause pump to operate at an inefficient point along the pump curve. This also wears out the rotating mechanical parts more quickly. 








AndreyT said:


> That's actually not accurate.
> 
> What you can a "mag drive" is actually an permanent-magnet synchronous AC motor (what is also commonly known as _brushless_ electric motor in DC terminology). I don't want to turn this into a lecture on physics of brushless motors, but I's still like to note that the mechanical load level experienced by the rotor will immediately and strongly affect the amount of electric current that flows through the stator windings. It is not even remotely correct to say that "electro-magnetic field does not care what the impeller is doing". The configuration of that electro-magnetic field depends critically on what the rotor (impeller) is doing and that configuration will greatly affect the reactive resistance of the stator windings.
> 
> ...


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## AndreyT (Apr 28, 2011)

keithy said:


> I don't mean to jump into this discussion. But the whole thing can be simplified to two words. Back pressure.


No, it can't be, which is what this thread is about.

As it has been stated several times already, the effect of "back pressure" is completely different on different types of pumps. There are positive displacement pumps that suffer greatly from excessive back pressure. And there are centrifugal pumps, which don't suffer from it at all (or at least a lot less). Aquarium filters use relatively weak centrifugal pumps.

We already established that. There's no debate about it. So, when after all that someone pops up out of the blue and suddenly announces that it is all about "back pressure" (which is the point we started from), we can just... well, give each other that perplexed stare and politely pretend that nobody said anything.


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## Green_Flash (Apr 15, 2012)

The Fluval canister I am going to use (G3) says direct from the manufacturers description that flow adjustment is perfectly fine to do and will not damage the pump.

I looked into this becuase I also am going to be reducing 5/8 tubing to 1/2 inch tubing so I can use 13mm lily pipes.


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## keithy (Jun 8, 2010)

AndreyT said:


> No, it can't be


prove me wrong. 




AndreyT said:


> No, it can't be, which is what this thread is about.
> 
> As it has been stated several times already, the effect of "back pressure" is completely different on different types of pumps. There are positive displacement pumps that suffer greatly from excessive back pressure. And there are centrifugal pumps, which don't suffer from it at all (or at least a lot less). Aquarium filters use relatively weak centrifugal pumps.


you're missing a point here. the thing is that those pumps are designed that way while your small impeller pump is design for a very specific purpose. 






AndreyT said:


> We already established that. There's no debate about it. So, when after all that someone pops up out of the blue and suddenly announces that it is all about "back pressure" (which is the point we started from), we can just... well, give each other that perplexed stare and politely pretend that nobody said anything.


I do not want to argue this any further with people who cannot respect or accept other viewpoint different from his/her own and thus try to berate others to shows dominance. 

so you're saying that all of the below are wasted words. I rest my case. Have a nice day.





AndreyT said:


> What you can a "mag drive" is actually an permanent-magnet synchronous AC motor (what is also commonly known as brushless electric motor in DC terminology). I don't want to turn this into a lecture on physics of brushless motors, but I's still like to note that the mechanical load level experienced by the rotor will immediately and strongly affect the amount of electric current that flows through the stator windings. It is not even remotely correct to say that "electro-magnetic field does not care what the impeller is doing". The configuration of that electro-magnetic field depends critically on what the rotor (impeller) is doing and that configuration will greatly affect the reactive resistance of the stator windings.
> 
> For these reasons, if you deliberately stall the rotor of the brushless motor (like block the impeller, for example), it will immediately result is significant rise of the current flowing through the motor and will eventually overheat it and burn it out.
> 
> ...


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## OVT (Nov 29, 2011)

keithy said:


> prove me wrong.


You are wrong. Multiple manufactures simply reduce/increase the effective ID for the flow control.


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## keithy (Jun 8, 2010)

OVT said:


> You are wrong. Multiple manufactures simply reduce/increase the effective ID for the flow control.


ok, OP you are right that it will not have 'very significant' impact, but that doesn't mean it have no impact towards the pump. It may be very little, but may be noticeable in the long run.

Being right or wrong should be reasoned. I sure do not appreciate being bashed for sharing my view.


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## HD Blazingwolf (May 12, 2011)

its not about proving anyone wrong or right., its about geting the facts out and having everyone learn in the process


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## OVT (Nov 29, 2011)

I think we are starting to go in circles now. If the 'extra load on the motor' is the only potential issue, then I can live with it.

My opinion/position on that specific subject comes from owning 3 Eheims 2026 and 3 Eheims 2075, all of them use the same 'restriction' mechanism to control flow. The oldest 2026 is about 14 years now with a single gasket change. I also tend to clean my filters infrequently, and that also effectively reduces the ID of the tubing. So, if that guy can run for 14 years with varying IDs then it can run for couple of more.

The only moving part is the impeller, and at ~$30 to replace, not a big price to pay for what I want.


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## PlantedRich (Jul 21, 2010)

OMG! Would some of you guys please call Eheim and tell them how screwed up and clueless they have been all this time? Of course they only deal with fish filters and don't go much into pumps larger than six inches across! 

It really should be time for school to start again so folks will have more to do!


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## GeToChKn (Apr 15, 2011)

OVT said:


> I think we are starting to go in circles now. If the 'extra load on the motor' is the only potential issue, then I can live with it.
> 
> My opinion/position on that specific subject comes from owning 3 Eheims 2026 and 3 Eheims 2075, all of them use the same 'restriction' mechanism to control flow. The oldest 2026 is about 14 years now with a single gasket change. I also tend to clean my filters infrequently, and that also effectively reduces the ID of the tubing. So, if that guy can run for 14 years with varying IDs then it can run for couple of more.
> 
> The only moving part is the impeller, and at ~$30 to replace, not a big price to pay for what I want.


I LOVED my 2026 and 2075 when I had bigger tanks and had them on them.


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## AndreyT (Apr 28, 2011)

keithy said:


> I do not want to argue this any further with people who cannot respect or accept other viewpoint different from his/her own and thus try to berate others to shows dominance.


You probably have a very unorthodox concept of "viewpoint", "dominance" and "being respectful".

What we are talking about here is not a matter of "viewpoint". It is a matter of very technical, factual and objective data. It doesn't depend on anyone's viewpoint, neither on mine not on yours. You know, 2+2 is 4 not because it is someone's "viewpoint", but rather because it is an objective fact. And when I state that 2+2 is 4, it is not because I disrespect people who believe that 2+2 is 5 and try to "dominate" them.


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## Mshen11 (Feb 26, 2013)

going back on subject... is restricting flow in eheim canister a good or bad thing?

ive also heard that it is ok only on output. or is it ok in either input or output? im wondering if i can put de-nitrate in the eheim canister and restrict the input to 50gph without damage


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## etane (May 14, 2012)

I have a 60P. I was using a couple of 5/8" - 1/2" barb converters to fit a 5/8" UV light tubing at the output of a Eheim 2236 canister. 

The barb converter itself is plastic and is rather thick. 

I used a sharp scissor to cut off part of the barb that wasn't necessary as well as shaving the inside wall to make it thinner. The barb converter still choked the water flow enough that the 2236 was producing a weak current even with it on full blast.

I've since tossed the plastic barbed converters and bought the glass Borneo Wild brand to do the same function. The flow is much stronger now but still not as stronger as when before.

So, anyways, the barb tubing size converter itself can reduce the flow even more so than the smaller size tubing.


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## wkndracer (Mar 14, 2009)

Great coffee read this AM. (old thread full of cold debate and opinions)

2215, 2026, 2075's along with a number of external and submerged return pumps are in use here and the double taps are primarily for canister isolation (cleaning purposes) not flow control. Ball valves included in a topic of intentional flow control is almost oxymoron LOL. 
I have only one Eheim with designed variable output. 

ALL closed loop systems (canisters) contend with "friction static head pressure" so it's not simply about the power needed to move water through the filter media. That's also why they all list maximum installed lift height. (my mind struggled with this years ago). You can't put the tank on the third floor and the canister in the basement and expect a closed loop 2075 to move any water. Size reduction to the inlet / outlet will increase flow restriction decreasing flow but no,,, you won't melt it down doing so. It will *slightly* increase the operating temperature of the pump but doubt you could identify it by touch. 

While not positive displacement by design as AndreyT detailed in brief a mag drive motor *is a drive motor*. To create force of motion stator and rotor have to magnetically couple. Coupled = EMF in play and should not be any point of argument. Ultimately restricting flow (increasing load) on any pump creates more rotor slip (motor) and slip = heat, even with a mag drive.

*Butt!* (everyone has one :icon_roll) Complete or near complete deadhead (stall) is required to cause any damage to a mag drive. I've blistered the plastic liner of the stator coil sleeve distorting it to the point the impeller rattled in rotation. Also distorted the rubber shaft bushings as well once. Both cases required inlet blockage of near 100% (neglect).

Reducing the inlet / outlet diameters and changing those pipe diameters or if only one is to be changed restrict the outlet only as best practice with no worries :smile:. The rest is a fun read.

Mshen11, as long as you don't completely stall the flow no damage will occur. Media load shouldn't be a concern minding that the system doesn't stall or get noticeably warm. Mechanical flow reduction should be on the discharge side simply as a basic rule of flow. 

etane, that barbed coupler acted exactly like an orifice (flow restriction). Smooth transitions make for less turbulence so you gained back some of your loss from the diameter change.


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## Mshen11 (Feb 26, 2013)

wkndracer

would your answer change if eheims are not "mag drive". there was another thread i read where there was a heated technical debate, no one can agree on anything except that eheims are NOT "mag drive"

what do you mean by 'stall the flow'.. I am thinking packing a 2217 (150gph+?) with de-nitrate which requires >50gph... all by dialing it down on the quick disconnects (and again where do I dial it down?). that's dialing it down 60%+


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## OVT (Nov 29, 2011)

This was actually fun the first time around and a re-read made me smile.

The filter in question is doing just fine, TYVM. It was cleaned once since the OP.

via Droid DNA Tapatalk 2


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## wkndracer (Mar 14, 2009)

Mshen11 said:


> wkndracer
> 
> would your answer change if eheims are not "mag drive". there was another thread i read where there was a heated technical debate, no one can agree on anything except that eheims are NOT "mag drive"
> 
> what do you mean by 'stall the flow'.. I am thinking packing a 2217 (150gph+?) with de-nitrate which requires >50gph... all by dialing it down on the quick disconnects (and again where do I dial it down?). that's dialing it down 60%+


stall = no flow, water flow through the filter is stalled, stopped completely or nearly so.

Close the outlet valve to your desired rate of flow and have at it. I would ignore the inlet piping doing as you propose leaving the valves full open. 

aside; Without the force of magnetic coupling (rotor to stator) a motor makes a poor paper weight LOL. Technical debates have real value only to a point on simple topics. 

(imo) K.I.S.S. or argue for entertainment.


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## AndreyT (Apr 28, 2011)

wkndracer said:


> ALL closed loop systems (canisters) contend with "static head pressure" so it's not simply about the power needed to move water through the filter media.


No, you got it completely backwards. All closed systems have _zero_ static head. Zero static head is actually the most important property of closed systems. This should be common knowledge, but anyway: http://www.fluidh.com/calcpumphead.html. The very idea of "canister filter" is to take advantage of the "zero static head" principle. 

(The only thing that has to be noted here is that the static head is equal to exact zero only if both the inlet and the outlet are below the tank water level. If the outlet is above water, as is often the case with spray bars, the system is no longer closed. The static head in such cases is not zero, it is determined by the distance between the spray bar and the tank water surface. I.e. even in such cases the static head is small and, more importantly, independent from the canister-to-tank height)



wkndracer said:


> That's also why they all list maximum installed lift height. (my mind struggled with this years ago).


That is incorrect. The first and the most important reason they put the height limit is the fact that the pressure inside the canister is proportional to the heght of the water column. The seals in the canister are rated only to a certain pressure limit, exceeding which will make them leak. This is the main reason canister filters have height difference limit.

The second, less important reason, is that increasing the height will simply increse the length of the hoses, thus increasing the drag-induced head.



wkndracer said:


> You can't put the tank on the third floor and the canister in the basement and expect a closed loop 2075 to move any water.


Oh, yes, you can. You can put it on the 5th floor and it will work. You can put it on the 20th floor and it will work. Just make sure you beef up the canister seals to withstand the static pressure produced by such water column (and, possibly, beef up the canister itself and the hoses). Again, the drag in such long hoses will reduce the flow, but it can be alleviated by using larger diameter hoses. 

As long as the system does not burst from pressure, and as long as it is not overwhelmed by drag, it will work flawlessly.



wkndracer said:


> Size reduction to the inlet / outlet will increase flow restriction, decrease flow and increase static head


This static head statement is, of course, absolutely incorrect. The static head is always exactly zero (assuming both pipes are submerged) it will neither increase or decrease regardless of how you change the hose diameter.



wkndracer said:


> While not positive displacement by design as AndreyT detailed in brief a mag drive motor *is a drive motor*. To create force of motion stator and rotor have to magnetically couple. Coupled = EMF in play and should not be any point of argument. Ultimately restricting flow on any pump creates rotor slip (motor) and slip = heat, even with a mag drive.


The first part is correct, the last might need some clarifications. Is a brushless motor slip is not necessarily bad. All brushless electric motors are actually designed to operate in slip mode under load, when the magnetic field in the stator rotates faster than the rotor. This is their normal mode of operation. This is how it is supposed to be. This is why brushless electric motors are useful in _static_ torque applications: they are routinely used to generate controllable _static_ force when the rotor is completely _stalled_, while the stator field continues to rotate. I.e. brushless motors can be used to hold things in place against opposing torque. (This is how brushelss motors work in electrically-actuated aircraft control surfaces, for one example)

However, I have to admit, I'm not sure that simple AC motor used in the aquarium pump follows exactly the same principle. In any case, it is true that increasing the load increases the amount of heat. This is perfectly fine within design limits.


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## Aquatic Delight (Mar 2, 2012)

just make sure to equally restrict your flow. i blew out the plastic housing on a canister filter once before, because i restricted the flow on the out hose, but not on the in hose.

my concern here is pressure build up. over time the excess pressure building up in your canister can cause seals to fail.

(if this has been covered i'm sorry but i stopped reading around post #25)


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## wkndracer (Mar 14, 2009)

Accept that I transposed static head with friction head and hope that you enjoyed posting the correction as much as I did reading it. 
(checking ego at the keyboard) Though I would love to read of someone placing a canister in the basement with the tank on the second floor to see it actually work.
Using a motor to hold loads with the rotor in static position against opposing torque is not what I would consider a common situation with most AC motor applications. Also do indeed give you that slip is a basic function in the operation of most motors. But, that's by design based on accepted loading for a given motor and the torque it's capable of generating. More often with the motors I'm familiar with sustained overloading creates a pole skip or even more common an overheated condition tripping thermal overloads. That's what I've seen occur most often when loads exceed motor rating. Locked rotors generally = damaged equipment, overtime and emergent work call outs. :smile:


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## etane (May 14, 2012)

wkndracer said:


> etane, that barbed coupler acted exactly like an orifice (flow restriction). Smooth transitions make for less turbulence so you gained back some of your loss from the diameter change.


Hmm can't understand why anyone would want tube size reducer that purposely maximizes flow restriction instead of minimizes it.

To me, it's a bottleneck. The glass reducer I replaced the plastic barb ones works much better and not sure what turbulence there would be within the tubing?


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## OVT (Nov 29, 2011)

etane said:


> Hmm can't understand why anyone would want tube size reducer that purposely maximizes flow restriction instead of minimizes it.
> 
> To me, it's a bottleneck. The glass reducer I replaced the plastic barb ones works much better and not sure what turbulence there would be within the tubing?


As an example, some crazy dudes (yours truly) run 300+gph rated filters on 17g tanks. The flow restrictions, in this case, is the least of my concerns. I just added a Fluval 404 dialed down to ~15% flow to a 30g. Why? That's what I had available on hand.

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## wkndracer (Mar 14, 2009)

etane said:


> Hmm can't understand why anyone would want tube size reducer that purposely maximizes flow restriction instead of minimizes it.
> 
> To me, it's a bottleneck. The glass reducer I replaced the plastic barb ones works much better and not sure what turbulence there would be within the tubing?


In the context of my post it's a question of manufacturing cost and quality. 

All these are rated as 1" connectors.









but measured ID??































These two are labeled as 3/4"

















Labeled 1/2"































1/2 to 3/4" connector.































 That thicker lip / facing edge on the cheaper connectors creates turbulence as the flowing water strikes that edge, like spraying water into a corner. 

(When buying a piece of milled lumber in the U.S. a 2x4 is 1.5"x3.5" not 2"x4".
Buying barbs and connector the ID doesn't always match the rated size.)

Valves are the same. (cost : quality)
Buying valves and plumbing materials remember that depending on what you are getting measurements can be in ID (inside diameter (most pipe)) & OD (outside diameter (most tubing)). *** Also you need to look at the valve seat area inside the valve (ID) because many are smaller than the spec. size. Valves rated @1" will be different even though all connect using 1" fittings.

Vermont American (USA) brass 1" gate valves have the full 1" flow path through the open valve with a *tapered ramp seat face.* 
(tapered ramp = less turbulence)

AB 1953 (china) brass 1" gate valves has only 3/4" through seat flow fully open and a *square cut seat face.* Installing that valve alone would restrict the whole system through a 3/4" reduction not the full 1" as the valve is rated.

Mueller (now Mueller Global = china) brass 1" gate valves are 7/8" flow through with a *square cut seat face.*

Buying tubing, pipe and fittings have the same concerns regarding rated vs actual ID. 

Here again square cut transitions are akin to spraying a hose into a corner. (lots of splash and wasted energy)

HTH


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## Mantis992 (Feb 13, 2013)

What reducing babrbs are you planning on using because I am planning on doing the same thing?


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## Mshen11 (Feb 26, 2013)

when you reduce like that, are the flow rate of the media reduced to that flow rate or is the media still subjected to the higher flow rate rated by the canister?


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## AndreyT (Apr 28, 2011)

Mshen11 said:


> when you reduce like that, are the flow rate of the media reduced to that flow rate or is the media still subjected to the higher flow rate rated by the canister?


Formally, it depends on the design of the filter. But AFAIK, most canister filters do not recirculate water internally, meaning that any flow reduction applied to the hoses automatically reduces the flow through the media in exactly the same way. 

Fluval 306 (and the series) do not recirculate. I see some Macro 75 canister filter sold on the Net that claims that it recirculates, but I have no experience with this filter.


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