# Canister filter have to be middle or can it be on the side with long hose/short hose?



## lnstevens (Aug 9, 2010)

I've run mine in the past w/ a long hose/short hose setup. Sometimes you don't have much of a choice. My 10 Gallon I had was on a counter so the canister had to sit beside it. When I had my 40B I had the canister out to the side a lot because of easier cleaning.

And the pump should work regardless of where it is pushing the water to or from. I will say I've always gone the inlet side for short giving me more freedom with the spray bar placement.


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## goodbytes (Aug 18, 2014)

It doesn't make any difference.


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## Diana (Jan 14, 2010)

As long as the hoses are fairly straight it seems OK. I have had problems when the hoses are so long there is a dip or curve in the path.


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## someoldguy (Feb 26, 2014)

Won't matter much . What matters is the head height , i.e. how far up the water needs to be pumped . Pumping from the canister to a tank on a normal height stand won't be an issue . Canister on the floor pumping up to the top tank on a 3 tier rack could well be.


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## SpaceLord (Feb 29, 2016)

someoldguy said:


> Won't matter much . What matters is the head height , i.e. how far up the water needs to be pumped . Pumping from the canister to a tank on a normal height stand won't be an issue . Canister on the floor pumping up to the top tank on a 3 tier rack could well be.



If the canister is in the stand or on the floor maybe almost no difference on how high it is. The stand height is only as thick as the wood on the bottom floor piece which is maybe an inch or something. 

Do you know which hose should be the long vs short hose? 

The intake(siphon) or the return water(connected to the pump I assume) 

Thanks


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## Doogy262 (Aug 11, 2013)

The return should be the short hose.


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## jr125 (Mar 5, 2015)

I have my intake and output on the same end. The return to the tank (spray bar) is near the top directed across the surface somewhat with the flow the long way across the tank. The filter intake is below it near the bottom and I seem to get a nice circular flow across the top and then back again across the bottom. As the filter is located near the same end both hoses are pretty short. If you are going to have one hose longer than the other I agree the return to the filter should be the longer of the two.


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## SpaceLord (Feb 29, 2016)

jr125 said:


> I have my intake and output on the same end. The return to the tank (spray bar) is near the top directed across the surface somewhat with the flow the long way across the tank. The filter intake is below it near the bottom and I seem to get a nice circular flow across the top and then back again across the bottom. As the filter is located near the same end both hoses are pretty short. If you are going to have one hose longer than the other I agree the return to the filter should be the longer of the two.


Will a longer return hose street the motors more to be pumping the water a greater distance? 

The siphon will just use gravity and suction from water following water down the hose. 

If this is the case, why would it not be better to have gravity move the water the greater distance and have the pump move the water up the shortest distance? 

Thanks.


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## Virc003 (Dec 3, 2011)

SpaceLord said:


> Will a longer return hose street the motors more to be pumping the water a greater distance?
> 
> The siphon will just use gravity and suction from water following water down the hose.
> 
> ...


Not sure about fluid mechanics but the explanation using basic physics (newtonian mechanics?) would explain your question. The only force acting against the flow of water is gravity and gravity only acts in the vertical direction (height). Thus lateral movement can be neglected since no lateral resisting forces are present. All other forces would be equal since its the same exact hose and would have the exact same fittings either way. Even if some other force is present, I'm sure it's small enough that for our purposes it can be negleted.


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## jeffkrol (Jun 5, 2013)

someoldguy said:


> Won't matter much . What matters is the head height , i.e. how far up the water needs to be pumped . Pumping from the canister to a tank on a normal height stand won't be an issue . Canister on the floor pumping up to the top tank on a 3 tier rack could well be.


There is an "opposite" problem as well.. Canister head usually needs to be lower than the tank rim (more correctly, water line)..sometimes by a few inches..

you actually have more "headroom" below the tank than above the tank..


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## Hsunami (Mar 10, 2011)

For my ehiem 2232 it didnt matter. I did have the intake at one end and the out at the other end and my caniser was on the side of my tank with no issue. I have tried swapping both and had no issues.

Right now my short tube is on the intake and long tube on the outtake and both are on the right side, still no issue. Have a circulation pump on the left side to circulate the water in a clockwise motion. This also helps diffuse more co2 before actually entering the tank.


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## roadmaster (Nov 5, 2009)

Once the pump start's the flow of water into the filter, gravity takes over just like syphoning water from a hose.
Pump does not have to work all that hard after that.
If you fill the hose that draw's water from the tank (close the valve on end of hose) when priming the filter ,you see how gravity work's when the water rushes into the filter when you hook up the hose and open the valve.
Pump only need's to start the syphon .
Doesn't really have to pump too hard after that due to gravity.


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## jr125 (Mar 5, 2015)

Virc003 said:


> Not sure about fluid mechanics but the explanation using basic physics (newtonian mechanics?) would explain your question. The only force acting against the flow of water is gravity and gravity only acts in the vertical direction (height). Thus lateral movement can be neglected since no lateral resisting forces are present. All other forces would be equal since its the same exact hose and would have the exact same fittings either way. Even if some other force is present, I'm sure it's small enough that for our purposes it can be negleted.


From my experience designing sprinkler systems I can tell you there is another factor working against the flow of water. It is the resistance of the water flowing through the pipes, tubing, fittings, anything it passes through. The result is pressure loss. This is figured just as pressure loss due to increase in elevation is. In this application it is probably so little it's not a real factor at all but it still is better to have the pump move the water through as little of this resistance as possible.


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## Wasserpest (Jun 12, 2003)

Jr is right. There are a few things at work here. "Head" doesn't really apply, as a canister filter is a closed system, unlike a sump, where head matters a lot. 
Increasing the vertical distance between the aquarium surface and the canister filter will increase (positive) pressure on the seals, which can lead to leaking, and it will lengthen the hoses, which increases resistance/friction as described above. You will notice that resistance when blowing through a garden hose to empty it.
Depends on the pump, but many impeller pumps work better pushing water than sucking it. So I think in many cases having a longer outflow and a shorter inlet beats the opposite. Otherwise, "cavitation" can occur. It's something you can try though - some canister designs behave differently than others, depending on the location of the motor etc.


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## Greggz (May 19, 2008)

From personal experience the question is not can it be done but should it be done.

The more direct path straight down to the filter, with the shortest hose possible, will create the greatest flow. 

The less direct the path, the greater loss of flow.

What is acceptable is up to you.


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## SpaceLord (Feb 29, 2016)

roadmaster said:


> Once the pump start's the flow of water into the filter, gravity takes over just like syphoning water from a hose.
> Pump does not have to work all that hard after that.
> If you fill the hose that draw's water from the tank (close the valve on end of hose) when priming the filter ,you see how gravity work's when the water rushes into the filter when you hook up the hose and open the valve.
> Pump only need's to start the syphon .
> Doesn't really have to pump too hard after that due to gravity.


The Siphon and gravity only account for 50% of the equation. 
It was my understanding that the pump can't create the siphon which is why many of today's canisters will have manual pumps to get the initial siphon started. 

The opposite end of that equation is returning the water back into the tank which is where the pump come back in. 

What I don't know if its just the vertical high or the length of the hose will make the pump have to work harder or not. 

Probably a PH.D in physics might know. 

Thanks


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## roadmaster (Nov 5, 2009)

SpaceLord said:


> The Siphon and gravity only account for 50% of the equation.
> It was my understanding that the pump can't create the siphon which is why many of today's canisters will have manual pumps to get the initial siphon started.
> 
> The opposite end of that equation is returning the water back into the tank which is where the pump come back in.
> ...


 Length of the hose.
If you think the pump must have other than minimal capability to pump the water back into the tank, then run a garden hose or python hose from your tank, across say thirty five feet and up into kitchen sink such as I do once a week.
Suck on the end of the hose to start the syphon,and the water empties from my aquarium's with no other mechanical help until the water level in the tank becomes lower than the height of the kitchen sink.(about 50 % water change).
Now that spring is approaching I can open patio door and drain the water onto flower's.Too cold for this during winter.
I only use sink adapter on hoses to fill the tanks and sometimes use pump attached to hose to pump water faster from the tanks but pump is a bit large to hang on the glass inside the tank, and it smooshes plant's if I set it anywhere on the substrate.
Mostly use the pump and hose in pleco tank that get's more frequent water changes.


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## SpaceLord (Feb 29, 2016)

Greggz said:


> From personal experience the question is not can it be done but should it be done.
> 
> The more direct path straight down to the filter, with the shortest hose possible, will create the greatest flow.
> 
> ...


Are you talking about flow loss from the incoming water or the outgoing water? 

Which one are you advocating as the long hose? The intake or output? 

Thanks.


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## Greggz (May 19, 2008)

SpaceLord said:


> Are you talking about flow loss from the incoming water or the outgoing water?
> 
> Which one are you advocating as the long hose? The intake or output?
> 
> Thanks.


Keep in mind we might be talking about shades of gray. The optimum would always be the shortest most direct route to and from the filter. In practice, any actual loss may be minimal, albeit still some loss.

Sometimes it helps to extrapolate ideas to ridiculous extremes. Let's say one hose is 50' and other directly into the tank. If the input into the filter is the 50' section, it is being aided by the siphoning effect. If the output into the tank is 50', head pressure will limit the flow back to the tank.

At least that is the way I see it, and has been my experience. I would put the longer hose on the input side into the filter.

Again, in reality, if the filter is well sized for the tank, you might experience minimal differences, and it might be much ado about nothing. Much like micro toxicity, others may argue otherwise.


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## jr125 (Mar 5, 2015)

roadmaster said:


> Length of the hose.
> If you think the pump must have other than minimal capability to pump the water back into the tank, then run a garden hose or python hose from your tank, across say thirty five feet and up into kitchen sink such as I do once a week.
> Suck on the end of the hose to start the syphon,and the water empties from my aquarium's with no other mechanical help until the water level in the tank becomes lower than the height of the kitchen sink.(about 50 % water change).
> Now that spring is approaching I can open patio door and drain the water onto flower's.Too cold for this during winter.
> ...


As the highest point of both the intake and return lines is usually the top of the aquarium the pump should only have to make up the difference in height between the intake tube (usually lower in the tank) and the discharge back into the tank. The pump would also account for any increase in flow rate than just gravity would provide. As both lines are equal in height at the top of the aquarium there would be no flow if not for the pump. On my filter there is a shut off that closes the loop to allow you to remove the filter without losing the siphon as long as the water level in the aquarium does not fall below the intake tube. When the filter is replaced and the shut of re-opened gravity will re-fill the filter and the lines until the water level in both lines is equal again. That being at the top of the aquarium. Then the pump provides whatever flow there is.


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## s_s (Feb 15, 2012)

A canister filter in not too much different than plumbing a sump. There's is one huge difference of course: with a canister filter, the "head" does not matter because the system is an entirely closed syphon. 

However, we also use a number of other factors when trying to calculate (and maximize) the total flow rate of a sump system. The more bends in the plumbing, the more resistance to flow. The narrower the width of the plumbing, the more resistance to flow and the longer the plumbing the more resistance to flow. 

So with a canister, we should look at all of those, as well. Bends, we should eliminate best we can, We don't have a choice on the width of the plumbing, *but where we put the filter does effect the length of the plumbing*.

Now it does not matter if the input or output is longer with a canister. As we said, head doesn't matter in a complete syphon. The water pushing down into the filter displaces the water flowing back into the tank. And vertical acceleration (gravity) is independent of horizontal acceleration. So as long as the input and output are the same vertical height it is a complete wash.

But total length of tubing provides resistance. This is why canisters have a "max head height". *And total length of tubing is increased when we deviate from placing the canister precisely in the middle of the input and output.*

Assume the input an output are positioned on either end of a 30 gallon tank with exactly 3 feet between them. Now, assume the head height is 3 feet. If we place the canister in the middle (Isosceles triangle base=3,H=3), the total run of our hose will be *6.78 feet* (sum of the two legs). If we place the filter one one side directly below either the input or output our total hose run will be *7.243 ft* (hypotenuse of SAS calculation + one side).

So how big of a difference does the extra ~6" make in flow rate? Probably not a lot. But is certainly doesn't make some.


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## Diana (Jan 14, 2010)

I have had problems when the screen in the tank on the tubing that leads to the pump gets clogged. Does not have to fully block the flow, but the pump has problems. Simply based on this, I would think this hose ought to be as short and direct as possible. The pump has a hard time handling a restriction on its inlet side. Pumps handle problems such as longer pipe or more fittings on the outlet side much better. I would still keep these to a minimum, though. 
If you need to slow down a pump, put the valve on the outlet side. 

A siphon starts with a tube full of water with the ends of the tube at the same elevation (no water moves). Then drop one end and water starts moving. Drop that end more and water flows faster. 
In the case of an aquarium the 'ends of the tubing' are equivalent to the water level in the tank. It does not matter if some of the tubing is higher or lower in the tank (the intake or the spray bar, or the intake of a gravel vac). The water won't move through the tubing by itself. The pump or gravity makes the water move. The pump is overcoming the friction in the tubing and fittings, and, in the case of an aquarium filter, the restrictions of the filter media. 

Try this: 
Set up your gravel vac and get it flowing. 
Then put your finger over the outlet and raise and lower this end and watch the flow when you release your finger. (keep the bucket handy!) 
If you want to stop the flow you can raise the end until it is equal to the water surface in the tank. (I clip it in place with the end just barely under the water). 
If I want to do a slower water change, I will place the bucket higher off the floor so the water flows slower. 
Now try this:
Get the longest piece of tubing you can. 
Coil it up so the smallest amount of tubing is coming out of the tank, and a short arch goes into a bucket. Most of it is in loops on the floor. Try to start a siphon. 
Now straighten it out, but make sure the outlet is the same elevation as when it was coiled up (no fair going out the door and down the stairs!). Try to start the siphon. In my experience, a straight line or gentle curve, even if it is a long one, will start easier than a siphon where the tubing is going up and down. The water level is the same (same aquarium) and the fall is the same (bucket is on the floor). But the route is different. 
A siphon in a hose works better with less twists, less 'over hill and over dale' but it will work, if you can get it going. It is much easier to get it started if it is closer to a straight line. 

Similarly, in setting up a canister filter, each fitting, each turn in the pipe causes the pump to work harder (even if the 'pump' is gravity) and the flow will slow down when the pipe is longer or more convoluted. 

A smooth pipe is MUCH better than a ridged pipe. Fluval ridged tubing may be easier to arrange, but I do not like the obstructions to the flow. 

I have seen a study where they set up several plumbing situations trying to assess which form of bends were least restrictive. 
They measured how much water the pump could move when it was pumping the water through various assemblies that turned the water direction 90 degrees:
A single short bend 90 degree (a standard sort of fitting)
Two 45 degree fittings. 
A 90 degree sweep (easiest to see if you look at pictures of electrical conduit)

The assemblies worked like this:
Short bend 90 was the worst. Use these only where you absolutely have to. 
2 x 45 degrees was significantly better. Worth the extra money to buy and install it this way, but took up more room. Still, if you can go this route, do it. 
A sweep was the best, but not enough better than the 45 degrees that it is worth taking up more room or more money. If you have the room, use a sweep. If you are short on space, and a sweep won't fit, or you cannot find a sweep, but can you get a couple of 45 degrees, this is a reasonable alternative. 

This test was using rigid pipe, not flexible. I have not researched it, but I think a flexible pipe with gentle bends would be better than straight pipe with fittings, but I am not sure. The material could make a difference, but I am positive that any smooth walled tubing will be significantly better than any ridged tubing.


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