Hello all, and happy freakishly early pool opening season this year.
Short story - Dynamo 1.5HP Dual speed pump on .75 (low setting) will not pump freely or as much as it should. Backwashing helps initially, then goes back to not wanting to push the water as much as it should. The pump reservoir (the pre-filter after the skimmer) was full last year when the pump was running at 1/2 power. (You know how you can sort of see the water sloshing around at the clear lid?) Now what happens is that over time, you can observe the water level in the pre-filter at the pump drop where the water level is barely at the intake line. Pump on full power works like a champ.
I just saw another thread that seems to have the same problem but mine is not that bad. In the other thread, the pump was just humming while sitting there and doing nothing. Mine sounds normal, it's just not doing what it's supposed to be doing. It's like it's loosing it's prime, but not all of the way.
Pump worked wonderfully for the whole one month that I had it running last year before shut down. (We had the pool installed near the middle of September.) So, the filter media is new, the pump is new, and backwashing seems to temporarily fix the problem. This tells me that I may have something clogging the filter, but I'm not so sure. When I run the pump at full power, I'm getting 10 PSI at the filter. (Normal from what I've read.) When the filter is on low power, I'm reading 0 PSI, which is what it's always done. Now if I had clogged media, wouldn't I get at least SOMETHING for a PSI reading even on low? There should be some indication of resistance of water flow if there was a clog, but there isn't.
Any ideas on what steps to take on this would be greatly appreciated. I suppose it's always possible to have a defective pump.