sump water return problem

[bpeitzke]

I have a 65-gal tank with a sump filter below, which houses the protein skimmer and return pump. I have a hang-on-back siphon return canister with dual large-diameter return hoses routing the water into the sump filter itself. I use an AquaLifter siphon pump to suck the air out of the siphon chamber to permit return water flow. I also use a prefilter on the intake of the AquaLifter.

Recently I've observed the return pump sucking air due to low water level in the sump, and have had to turn off the pump, skimmer & Aqualifter to avoid tank overflow. I've experimented with new AquaLifter pumps, new prefilters, and replaced the tubing involved. None of these actions have had any effect, and I still cannot run the recirculating pump. When I start it up and watch the siphon chamber, I observe that the AquaLifter has sucked most of the air out of the siphon chamber, and return water is flowing, but apparently not at a rate adequate to match the flow of the return pump, thus causing the water level in the tank to creep up to the rim. The air bubble in the siphon chamber does appear a little larger than it used to be.

I'm at a loss with this system. When I test the several AquaLifter pumps (some brand-new), they seem to have strong suction. I've also run it briefly without a prefilter, and still had the rising water level, so it seems air leakage in the prefilter is not the cause.

Maybe AquaLifters are just not up to the job? Or maybe I have a crack in the siphon canister?

Appreciate any advice!

Bob

 

[Retired_AF]

Have you check your lines for debris clogging them?

I recently had a similar incident where my drain line got mostly clogged with plant material and the pump worked as advertised and pushed water up until it started sucking air, nearly overflowing my tank.

 

[bpeitzke]

Fixed it

I took my siphon canister off and checked every part of it. The dual lines that return the water to the sump were totally clear and I could find no cracks. Turned out that the air extraction port on the top of the siphon canister was blocked, so the AquaLifter was sucking hard but not able to pull the air out. Once I cleared that port and put it all back together, and primed the siphon port, it started working fine. Next time I'll know what to check first.

Bob