Sand Filter Pressure Rising Quickly

[dborg]

Have Triton II sand filter and been experiencing filter pressure rising quickly from about 10 PSI to 28 PSI in about 30 min. Have just replaced the O rings in the slide valve. With increased pressure pool vacuum quits working. When cycling power to pump pressure will usually drop back to 10 PSI. We have little air bubbles coming out of the inlets. Any suggestions?

[PoolDoc]

Hi Dborg;

I've gone over the layout of the filter in my mind several times, to see if I could think of anything that could cause the pattern you describe. I'm going to ask Poconos, Waterbear and Waste to take a look.

BUT . . . please tell me the following:
#1 - where is your gauge - on top of the filter?
#2 - have you been tapping the gauge (just flick the face with your fingernail) before taking readings? If not, do so.
#3 - what sort of gear or valves is there DOWNSTREAM of the filter?

Also, if you can send me pictures of your pump, filter & downstream layout, that would probably help -- send them to poolforum AT gmail DOT com.

Ben

[Poconos]

Assuming the equipment is in a standard configuration, skimmer, pump, filter, returns, with the pressure gauge reading the filter INLET pressure. I also assume you are using filter sand.
I've seen similar bahavior, although not to the degree stated with the pressure rising 18 psi, if the filter has trapped small particles. I've seen it after adding DE to a sand filter. Almost like shutting off the pump momentarily allows the fine stuff to 'float' again inside the filter. After operating for a while this small stuff cakes on top of the sand and causes the pressure to rise. An 18 psi rise seems a bit much though.
When you kill the pump do you see any backward flow out the skimmer? My thinking is a big air bubble in the filter that is compressed while the pump is running and going back to atmospheric pressure when the pump is turned off. This could cause a lot of churning in the filter. Much more than if there was a solid charge of water. Filters are normally designed to bleed off any trapped air.
Best thoughts for now.
Al