Water Flow / Pump Issue

[jthatch]

Hi,
I have an 18,000 gal in ground salt pool with a 60 DE filter on an AutoPilot system. I opened the pool last week and found I had some water issues, mainly some algae. I spent the last several days treating it with dry acid then shock and clarifier. During this time I backwashed the filter several times and added new DE. The pool ran perfectly fine during this period except that I did notice that when I backwashed and then turned the pump back on with filter, the water flow would take longer to start (at least a minute or two). Yesterday, the water was free of algae and ready to go with remaining treatments, so I backwashed the filter again and then took the filter out and washed it real good. After I put it back in and started the pump back up, I again did not get an initial water flow to the pump. But, this time it didn't even come after 1 or 2 minutes. I ran the pump a little longer and the flow eventually started. However, it only lasted about 20-30 seconds and then abrupty stopped. I checked all the baskets, manifold filter, plumbing leaks, silicone on O ring, clogged impeller, etc. I also tried turning the inlet valve back and forth with pump running. Each time I tried the pump again, I got same results. Filter doesn't pressurize and with air valve opened, nothing comes out. When I turn the pump off, water backflows into the basket chamber from the pump. The only thing I can think is that a skimmer line is either clogged or an air lock or would it have something to do with the main drain? But I would guess that if I get a surge of water through the line then maybe not? Being that the last thing I did was clean the filter, I thought it may be related so I turned the pool to re-circulate and tried the pump again with same results. I am not sure whats going on here and would greatly appreciate if anyone could lead me in the right direction.

Thanks, JT

[burtons81]

did you try blowing the lines out with a compressor, there might be something caught in one of the lines