# Canister filter sucking air?



## Wasserpest (Jun 12, 2003)

Over the last couple of weeks, one of my XP3's developed this most disturbing behaviour: It started to fill up with air, clearly visible through the canister housing. Every evening, the level went down to about 2/3. Tilting the canister would send air blowing out the outlet hose.

First I thought I had not connected it correctly, or one of the O-rings was not sealing. But repeated cleaning and assembling didn't make the problem go away.

I checked all of the inlet hose connections - tight! No air entering anywhere.

As a last resort, I changed the input strainer. Instead of the stock plastic strainer, I DIY'd one with a plastic hair roller, and some thin filter sponge ("sleeves" for magnum filters) around it, which distributed the sucking power.

Immediately, the filter was full of water, no more noises, no more air!!

Lesson learned: Plants provide oxygen. If you plant plants (java moss, in my case) underneath the inlet strainer, same oxygen will get sucked into the filter. Some strainer modification that will avoid that will help!

I might go back and try running CO2 into the filter, now that it is full of water.


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## Rex Grigg (Dec 10, 2002)

Also if the inlet strainer gets clogged up it can cause this same problem as the pump will for a short while pump more water out of the filter than is coming into the filter.


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## putty (Nov 19, 2003)

I had some major issues with the XP3 blowing bubbles for a while. Interesting enough, it seemed to fix itself. I think if you use filter felt and build up too much resistance to flow through the filter, it will suck air through the seal. 

I cleaned the filter media and it seemed to stop for about a month now. 

Check the surface where the seal sits, sometimes there are some imperfections there thay may cause issues.


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## Wasserpest (Jun 12, 2003)

Well the problem totally went away... and I am one happy Filstar owner again.

I was just so happy to find this (in hindsight obvious) solution, wanted to share it in case anyone has had similar problems.


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## anonapersona (Oct 19, 2002)

*cavitation*

I suspect cavitation, when the pump has resistance on the inlet from dirty pad or other obstructions the impeller can create a low enough pressure that gasses are pulled out of the water (oxygen or other gasses) and release as bubbles. 

Of course, this will depend on the obstruction, the pressures imparted at the impeller, and the gas content of the water. So, some units might do this even when clean if the gas content of the water was high, while others might not under the same conditions.

And this assumes that the seal is not leaking -- if it were you'd get a puddle when the canister was not flowing for the actual pressure in the canister is more when it is stopped than when the pump is running.


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## PlantumOfTheOpera (Mar 12, 2003)

*Gas Pains*



Wasserpest said:


> Well the problem totally went away... and I am one happy Filstar owner again.
> 
> I was just so happy to find this (in hindsight obvious) solution, wanted to share it in case anyone has had similar problems.


 Thanks for posting this, because I am STILL having the identical problem. I wonder if your/our problem will return upon running the CO2 though the filter again. 
Each night, my filter needs to be purged of 2-3" of gas. I, like you have been using my XP-3 as a CO2 reactor. I question if the gas is O2 or CO2, and if I should switch to a reactor inserted on the outlet side. My prior filter was a Magnum 200 on a smaller tank, which did not seem to suffer from gas accumulation. 
FWIW, I have tried running the top media basket with a more dense material than supplied, and have tried it empty. I have also completely cleaned out both tubes. 

I welcome more info from you and anyone else as I have become frustrated with an otherwise fine filter.


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## Wasserpest (Jun 12, 2003)

Hi POO, long time no seen!

I have stopped using the canister as CO2 reactor a long time ago, so the recent air buildup was definitely not caused by that, instead by O2 from photosynthesizing plants.

I believe the gas that collects is not CO2, but O2.

I also think that if there is a little bubble or airspace in the filter, it "attracts" dissolved gas (O2) in the water. In the afternoon, when O2 saturation of the water occurs, the bubble builds up quickly.

I suggest you run the CO2 on the outlet of the filter! Also, if there is still air in the filter, see if you can modify the inlet strainer. Make it larger so the resistance for the pump is reduced, and place it in an area where there are no plants underneath it. Maybe try what I did and use a Magnum prefilter foam sleeve and wrap it around some perforated object to reduce resistance and keep bubbles out.

Currently I am using an "internal inline" reactor  which works great, and letting CO2 bubble into the inlet again would be more of a test than necessity. Haven't tried it yet since I am so happy with my canister that is full of water!


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## Georgiadawgger (Apr 23, 2004)

Hey POO (boy, that sounds kind of funny), I used Wasser's internal inline reactor setup for a bit when I was using DIY and it worked great. I think everyone that has an XP3 has found that running CO2 into the intake can cause some problems (i.e. previous posts by all of us and Rex). I liked the internal inline reactor since it did a good job with dissolving CO2, but once I went pressurized I rigged an external setup.


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## PlantumOfTheOpera (Mar 12, 2003)

Wasserpest,

Thanks for the welcome, I had no idea anybody missed me :icon_bigg I have been dealing with other pursuits, and a major F%^^43p with my tank that killed off a lot of fish and plants. Have restabilized and gotten things back in order, so I am now attending to small problems, like the gas accumulation. Fortunately and coincidentally for me, you started this thread Thanks!

I did an experiment: I lifted one latch and held a candle at the edge of the canister while the gas was purged. The flame was diminished, so it is most likely CO2, and not O2, or the flame would have been augmented. As a result, I am looking into getting or making a reactor to plumb inline with the outlet from the Rena. I also would like to plumb my AQ heater into it; a submersible type. I am disappointed that the Rena behaves this way. Oh well. 

Georgiadawgger
POO comes from _P_lantum_O_fThe_O_pera, or generally what my wife refers to me as. <g> I skipped the DIY CO2 and went straight for the bottle. Now I have to get a reactor. Did you make yours or purchase it. Is it plumbed into the outlet from your filter, or is it plumbed separately?


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## Georgiadawgger (Apr 23, 2004)

Hey, I actually made one. I used a gravel vac tube (1 1/2 inch diameter...well a little bit bigger) as the clear center, a 1 1/2 "cleanout plug" and 1 1/2 coupler for the other end. I used two 90 degree 1/2 inch hose barbs at both ends and a 1/8 inch airline barb that goes into the "cleanout" plug end. I filled it with bioballs and used PVC cement to put it all together. For the cleanout plug I used teflon tape. I have it hooked up inline with my UV sterilizer on my outflow of my XP3. It works great!!! The picture below is what I modeled it after.


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## Wasserpest (Jun 12, 2003)

PlantumOfTheOpera said:


> I did an experiment: I lifted one latch and held a candle at the edge of the canister while the gas was purged. The flame was diminished, so it is most likely CO2, and not O2, or the flame would have been augmented.


First of all, I am glad it wasn't H2!! :tongue: 

BUT, I don't think your experiment is really conclusive. Could have been that the escaping gas blew air against the flame? Or it wasn't pure O2, maybe some N2 mixed in?

In any case, let us know how it goes without the CO2 in the inlet. If you still have the problem afterwards, think about the input strainer stuff that I mentioned before.


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