We finally have opened the pool this year, but things are going anything but smooth.
We bought a new pump last summer - the one we had (2.0 hp) would shut off when it rained and then wouldn't work for several hours, then would work again. After we purchased it, we had less rain and we ended up being gone much of August, so we never switched out the pump. Fast forward to this summer. We decided to put the new pump (1.5 hp) on and get rid of the old one. After a few issues of holes in hoses, broken lateral in sand filter, we got things running.
We have quite a bit of dead algae and dirt on the bottom, no leaves to speak of. I attached the suction vacuum.....Now we have an issue. After running the vacuum (manual or automatic) for anywhere between 30 seconds and 3 min, the system will start to lose suction and the return flow goes to almost nothing. I disconnect the vacuum, and it remains at the low suction. I then turn off the pump for a few seconds and when I turn it back on it works fine - until I try to vacuum again. During all of this the pump basket pot does not drain out like it does when it is sucking air. To further complicate things, the vacuum was not attached this afternoon, after several hours the suction was decreased by a large amount - almost like when the vacuum is attached.
My husband thinks that the 1.5 hp pump is not strong enough to run the system and the 250 pound sand filter. I have seen you all recommend smaller pumps, so I don't know what to think. I can't even find 2.0 hp pumps online. I can't vacuum the pool the way it is. I tried a new vacuum hose and it still does it. I am going to see if I can find a new skimmer vacuum plate locally tomorrow and test that. I don't know what else it could be.