i have a 40,000 gallon backward L shaped pool.
has a skimmer in shallow and deep ends & and a drain at bottom of deep end
just replaced a bad vari-flow valve this year and had no problems except for air pressure building up in sand filter.
i have worked on the pool for years and never had it build up pressure so quick. and i cant use my timer because i have to release the pressure everytime before i cut the pump off.
when i removed the old valve the sand filter drained completely. when installing the new valve i just reconnected it to the filter dry. was that okay?
if the pump cuts off with the air pressure built up and does not get released it will force all the water going into pump to go backwards back towards pool. and when the pump is turned back on water will not flow. i have to take a water hose to fill the pump filter back up with water and turn pump on. then i have to repeat a couple more times to get the water flowing again.
the sand has not been replace for probably 7 to 9 years