Pond Boss Forums AERATION Systems questions Check valves

Membrane diffusers usually have built in check valves. Rarely are the slits in the membrane adequate to stop water back flow. Checking function or mechanism of he membrane diffuser is caused by water pressure pushing in or down on the built in 'check valve' which stops water back flow. Dirt and detritus can build up inside or underneath the membrane. Membrane slits are usually 0.5-1.0mm and phytoplankton, sticky slime bacteria and detritus are often the sizes of 0.00001 to 0.005mm, thus there are lots of things that can build-up and collect or coalesce under and on the porus membranes and at the site of the check valve which is another reason IMO to periodically clean diffuers. Diatoms are able to grow on glass (periphytometer samplers) and stick tight enough they have to be scraped off with a razor blade. Periphytic algae has no problem sticking to rubber.

Efficiency of operation of the check valve can be verified with the use of a pressure gauge. Watch gauge when compressor starts. Pressure should rise to above normal operating pressure for 1-5 sec then fall back to normal operating pressure. If pressure remains high for longer than a few seconds the pump is pumping water out of the airline due to check valve leaking.