Pond Boss Forums AERATION Systems questions Check Valve Advice and Questions

I have a small rotary vein compressor attached to an old style air pod diffuser by way of 3/8" heavy set tubing. My problem is that I can't close the relief valve all the way during startup because the back pressure is too high for my pump. I would like to pump as much air as my compressor can handle, but its just not possible unless I'm there to manually control the relief valve until the pressure stabilizes.

What type of inline checkvalve do you recommend I use? Also, does it matter where the checkvalve is attached to the line? Does it have to be near the diffuser or can it be attached near the compressor? Sorry for my ignorance with this aeration stuff.

You can get inexpensive vacuum check valves at an auto parts store. Best location on stone diffusers would be at the stone split. Old Chrysler brake boosters used a 3/8" inlet and outlet check valve available in all Dorman "Help" sections.

A better solution would be to upgrade to membrane disc diffusers which are self-sealing and provide FAR better performance.

Rainman is right about the diffuser. For the first year I used the stone that came with the windmill. After reading numerous testimonials, we bought the membrane diffuser. The air stone made nice bubbles but the membrane diffuser made a WORLD of a difference. We now have hardly any bubbles appearing at the surface but the column of water rising up creates the illusion of a deep spring coming to the surface (the color of the water is darker). After seeing the difference, I have to say that the stone is just a bubbler.

Just to make sure I'm understanding ya'll correctly, the diffusers don't need a check valve?

Thanks for the advice.

The membrane diffusers don't need a check valve. The membrane has thousands of laser cut slits that open when pressure is applied by making the rubber "dome" out and spreading open the slits. When pressure is relieved, the rubber membrane flattens back out and self-seals. IIRC, Vortex diffuser slits are .5mm size whereas most others are 1mm in size. The smaller bubbles will move more water as they rise.

Thanks Rainman. I know what I need to buy now.

I wanted to chime in on this one...

It is correct that the membrane-type diffusers do have integrated checkvalves whereas the membrane will collaps on to the supporting disc or tube (depending on the type of diffuser you purchase).

If you look at all of the suppliers, we still include a "Blue" Brady Check valve as a secondary check to the standard check provided by the membrane. This is due mostly to the seeping of the water through the slits and eventually into the air supply line.

Yes, eventually the water will be pushed out by the compressor but it will overwork the compressor unnecessarly until it does.

Most membranes offered by companies are now automatically cut with 500 micoron or 0.5 mm slits to allow for the smallest bubble size. As Rainman stated, the smaller the bubble the more bubbles are allowed the greater the surface area and the greater the lift.

There are reasons behind thing that have been done to systems to keep them as maintenance and trouble free and this is one of them. If I can make a recomendation, do not skimp on this one.

Check valves are pretty cheap comapred to the rest of an aeration system. And sticking them in the lines during installation takes very little time.

I guess I'll start shopping for a membrane diffuser for the future, and use a check valve for now. Just have to go for a swim for my diffuser so I can insert the check valve.

Thanks again everyone.

In my opinion, the best check valve is gravity. That is, if at all possible, place your compressor above the high water line. Water doesn't flow uphill.