# Air in Rena XP4 filter



## pogobbler (Jan 12, 2013)

I bought a used Rena XP4 filter a while ago and have had it running on a tank in the garage to get the bacteria all set up and ready to go in the filter when I move the tank into the house. The filter runs just fine, but I find that over time, I do find air in the filter, around an inch or so can be seen at the top through the side of the filter. One time the filter was running for days without any air in it, I found a slight amount of water leaking out where the power cord enters the filter. A while after I raised the cord to keep the water from coming out, there was air in the filter again. I can't say for sure those things are connected, but the air did come after I raised the cord. I read on the manufacturer's faq that water leaking out from where the cord exits the filter can be a result of the filter being too far below the water surface, but this is just a standard 75 gallon tank, so the filter doesn't exceed that limit.

I've used the manufacturers recommended procedure to get the filter full of water and start it up, I've used a similar but somewhat different method I found on youtube specifically designed to rid any air from the filter, and I've tried my own method of filling up the main body of the filter with water then putting the top on, which is a little messy because of the displaced water, but it leaves little or no air inside. Then I hook it back up as normal, open the valve and start it up. In each case, though, over the next day or two, I end up with air back in the filter. Turning the filter this way and that and shaking it does cause it to expel some air from the output, but it doesn't noticeably affect the amount of air I can see inside the filter, and never gets rid of all of it.

The filter works fine other than this, it's really more an issue of the extra noise and the fact that the air just shouldn't be there. Anyone have any thoughts, experience, or advice?


----------



## grogan (Jan 23, 2011)

Hmmm sounds like there could be a leak on the intake side of things allowing the filter to suck air. Sometimes a small leak in the intake wont even leak water so they can be hard to find. Try turning it off and look for leaks. My eheim is doing the same thing and I still havent been able to find the culprit. It is especially frustrating in my planted aquarium because uncontrolled o2 at the wrong times will allow my precious CO2 to escape. Good luck.


----------



## emc7 (Jul 23, 2005)

My magnum 350s do this. The fix is usually a new o-ring and/or a little grease on the seal but it could also be in a valve. Check all the connections.


----------

