Printable View
I had exactly the same problem. I've spent the last two hours checking for air leaks, then it struck me. "What if the water isn't getting to the pump because of an obstruction?"
I opened the pot and felt for the passage between the pot and the impeller (with the pump off and unplugged!) sure enough it was clogged ith vegetation! It must have found its way past the basket. Cleaned it out and the jet is noe like Old Faithful!
chalk up another vote for impeller blockage. do you have a dog swimming in your pool by any chance? my golden retriever's hair - at least some of it - gets past the pump basket and gums up the impeller, which causes a very noticeable drop in pressure.
if you or someone in your house has very long fingers, there's a chance you can reach into the channel from between the area where the basket sits and the impeller. i can on my pump, and almost every time the pressure seems unusually low, i'll find some stuff gumming up the impeller.
if you can't reach in there, you may have to take the back of the pump off in order to get at the impeller.
sometimes, the sand "channels" and you lose backpressure since the water takes the path of least resistance - meaning through the channel, if you take the multiport valve off you might be able to see if there are channels - they look like cracks in rock.