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rjordan390 02-23-2012 02:55 AM

Trapped Air & Tiny Bubbles
I have the Rena xp3 cannister on my 75 gallon tank and most of the time when I do maintenance to clean the filters, I end up with a continous stream of tiny bubbles. I checked the mfg instructions for filling and priming the cannister and inspected the main seal for dirt. All seems to be ok. I think I found the cause and suspect that air is entering the suction line at the inlet pipe cap that is located at the top of the tank and is used for priming the suction line. This pipe cap has a paper seal and I voiced my concerns about it to the mfg spokesperson. This is the same type of seal one finds inside of a ketchup bottle cap or any other condiment.
When ever I need to close off the water and suction lines at the cannister and pull out the top assembly, I can hear air escaping. The cannister is has only been in service 4 weeks. There is no water leaks whether the cannister is running or off. I removed the plastic clamps from the suction side lines and replaced them with stainless steel worm clamps. The mfg is sending me another inlet assembly but I told them that I do not think that will solve my problem.
I will be shopping today to see if I can find a rubber flat washer that will fit inside of the inlet pipe cap and hopefully solve my problem. "Your Thoughts".

Tazman 02-23-2012 08:59 AM

Make sure the length of your tubing is as tight it can be, without restricting you moving it for maintenance.

Do NOT put a rubber seal on the vent cap, they are not designed for them, it has to be able to suck air in, in the event of a power failure, that is one of the siphon breaks.

Do you make sure you use the handle on top of the assembly before removing the motor housing cover?

rjordan390 02-23-2012 05:58 PM

<Do NOT put a rubber seal on the vent cap, they are not designed for them, it has to be able to suck air in, in the event of a power failure, that is one of the siphon>

but it is not a vent cap or why would the mfg put their own seal in it. I noticed when I try to fill the cannister, there is a visable 3/4 inch gap where the water level stops. And this does not include the area I cannot see. If a power failure would occur, no flood would occur. My cannister sits on the bottom of the cabinet. it takes water in and pumps water out. No siphon break is required.
I believe I know what you are saying but it applys to a differant set up.

Tazman 02-23-2012 06:26 PM

When you've filled the intake, cap it, run the filter, if it goes too low turn it off.
Release one of the clamps (without lifting the purge handle) and you'll hear air as water siphons into the filter and the level will rise quickly, make sure you keep your hand on the clamp so it doesn't overflow, clamp it when the level is high enough and plug in to start. The level should remain where it was when you clamped it.

Mikaila31 02-23-2012 07:10 PM

Its because you are priming it as the manufacture recommends... The result is air trapped in the filter. I have a 7 year old rena XP3 and it does not have this problem. I've NEVER primed my filter either. I don't see what the difficulty is on just filling the canister before starting it back up. I'm sure priming will work, but it won't fill the canister all the way. The method to vent this air was explained by Tazman.

However if the priming cap is leaking you CAN seal it. I rarely remove that cap and mine seems to seal just fine. You are right that it is not a vent cap. It is meant to make an air tight seal. You can put a rubber seal in there if you want. If I personally had that issue I would just seal the cap with silicone and leave it at that....

I tested your theory by fully unscrewing that priming cap with the filter running and mine drank a LOT of air lol. It took me like 5 minuets to get it back to proper near-silent operation. I vented off the stuck air about 5 times letting the filter run in between.

When I do maintenance on the filter once it is clean I place it in a sink or tub. Then I fill the canister with the top off and the media baskets in it, with tank or dechlorinated water of course. I fill it full then place the motor on it. This pushes a lot of water out of the filter and makes a small flood lol. It completely fills the canister though and no air is left. You need to hold the media baskets down and be fast with the motor or they will float and get out of alignment. Other option is to prime it then just vent off the trapped air repeatedly until its all gone.

I'm not sure why you are remove the assembly so often. I take mine out like once or twice a year to clean it if it needs it.

rjordan390 02-24-2012 04:09 AM

The reason I need to clean the media and cannister often is because I thought I did a good job rinsing the dust from the Flourite Red gravel. I worked about 2 hours rinsing seven 15 lb bags of it. I was hoping the remaining dust would settle all the way to the bottom of the gravel. But the dust turned out to be more then I thought. I am thinking of pulling everything out and cleaning the gravel again using a differant method. I believe trying to siphon it all out would be more work then taking the tank down.
When I try to re-arrange items in the tank, the dust I stir up is enough to dirty up the media.

Thanks to Tazman for the tip of removing one of the clamps.

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