Pond Boss Forums AERATION Systems questions Valves on rotary vane compressors?

Theo you are correct "if" you could stop air from coming out of the top,(or anywhere else too) any type of compressor/ diffuser system will bleed down in time when it is shut off for a period of time, thus letting water seek its highest level. The systems just dont stay air tight. Where does the air go "dont know" perhaps same place the air in a tire goes that does not leak but loses pressure over time. A back check valve prior to the intake will prevent this from bleeding off quickly,and if the pump is located at or below water level a backflow or syphon back thru the compressor "may" not take place.Seems when starting switches and or start capacitors get weak on rotary vanes they can restart in reverse.We have seen this with power surges and years of operating time and a new capacitor or start switch usually returns the motor to correct direction.For the soaker hose type membranes a check valve at the diffuser is the only place to have them, anywhere else and as BZ comments will have to push the water out of the line.A lot of the checkvalves used are made by Brady and are 3/4 inch and have a rubber o ring on the seat for a seal. These orings do not last long and I think at times do not seal well. I have not found a source for these orings and seldom talk to anyone that uses these check valves that realize the valves should be taken apart yearly to see if the ring is still good, just another item to maintain in this type of situation.The main problem are the organics and calcium that build up on the inside of this type of diffuser, Most vane pumps used in pond aeration are 10 psi models and normally pushing water out of any diffuser will exceed this 10 psi limit, Having a relief valve set at 10 psi in this case will keep the pump from over pressurizing until the water is out of the line.I prefer to have the water on the outside of the diffuser and only normal clean condensate on the inside.Moisture back into the pump either a vane or a piston is what will shorten the life of these pumps along with excessive heat, Keep them dry and cool and any pump should last for many years.