Another point on water in lines.
I do not run my system over the winter. Sometimes water will accumulate in the lines over the off season. Maybe the check valve leaks, maybe a hose clamp joint, who knows why, but sometimes it happens. Not all the time, but sometimes.
As an example, when I started up my system this spring one diffuser would not come on line immediately (out of a total of three individual double diffusers and two single diffusers for a total of 5 different separate air lines).
Water had filled the line presumably up to the pond surface level. When you start trying to push air through a line filled with water and force the water through the tiny holes in the diffuser the water, being more dense, takes a lot of time to flow through the tiny holes and escape to finally let the air start doing its thing.
This can lead to some problems if not handled correctly. In my case early in the spring I was running a linear diaphragm pump. I just let it run at stall pressure (around 5-6 psi) and after about 5 or 10 minutes the water cleared and everything was fine. I have since installed a Gast rotary vane pump to run three of the five air lines (the three double diffusers in my main pond). Had I done that with the Gast and if it was on a single line (with no other diffusers to bleed the pressure) it would have taken the rotary pump to whatever stall pressure it would produce (something well above its design pressure) and likely done one of two bad things or perhaps both. It could balloon the diffuser up beyond its stretch design and blown it out. It could damage the vanes in the pump by over pressuring it.
So any start up with significant water in the line should follow some precaution. Bill Cody will tell you to protect the pump by installing an over pressure valve - a good idea. This will protect the pump. But it could still WAY over stretch the diffuser (assuming it is a membrane type). So the way to prevent that would be to have a pressure gauge installed on the line (or at the pump) and a bleed off valve to bleed excess air while the water is being expelled.
In other words in my situation, next spring when I fire up the system for the first time this will be my procedure. I will open a bleed valve before starting the pump. I will start the pump then slowly close the bleed valve watching the pressure gauge. My diffuser depth is around 9 ft so it takes about 4.5 psi to overcome water head pressure at that depth and make air come out. Actually I know from normal operation my pressure gauge reads just over 5 psi. So I will close the bleed off valve only till the pressure reads 5.5 or maybe 6 psi. I will watch the diffusers. If air starts flowing out of all of them and I see this at the surface of the pond I will close the bleed valve completely and good to go. If one or more diffusers do not operate I will leave the pump running with the valve open, operating it to maintain 5.5 psi or thereabouts, till I do see air at all three stations. Then I will close the bleed valve completely.
By doing this, any entrapped water in the air lines will be given time to escape the diffuser heads tiny holes slowly without damaging my pump or the diffuser membrane.
I have no idea if that is the correct way, just my way.
Last edited by snrub; 06/25/18 12:57 PM.
