We have a 10,000 gallon, inground pool.
Whenever I switch suction to main drain only, the basket at the pump immediately fills up with air. Not completely, but enough to cause a lot of air to come out of the return jets and lower the pressure on the filter.
The same thing happens if I close off the main drain & attach my pool cleaner or even the old-fashioned hand vacuum in the skimmer basket. I can't use my cleaner any more, and vacuuming has become a nightmare. The pressure goes up & down between 0 and 5 (our normal is 10), and it takes FOREVER to vacuum this way.
We have a Hayward Super Pump, a brand new Hayward Star Clear Cartridge Filter, and our cleaner is a Hayward Navigator (which has been completely overhauled).
I'm so disgusted, I've only used the pool twice so far this season.
Thank you, in advance!!