Hello all! This is my first post but I've been here reading all the tutorials and advise from other threads for about a year and a half now, since I've purchased my first home with a pool. So up front, thank you guys for all the information i've gotten already from this website and your collective knowledge!
So, a little info on the pool and my history with it: Its a 30,000 gallon rectangle at 18'X36' with a small 9' deep end with really steep taper down to it. It was built in the 80s sometime from what I can gather from permits and paperwork the previous homeowner left. It has one main drain at deep end, and one skimmer basket, and one return jet. The return jet is on the far right side of the 18' length while the skimmer is on the far left.. This produces kind of a horse shoe flow on the surface for skimming, and that seems to work alright.
It has a 1 HP Sta rite Dyna Glas pump.
sand filter: Hayward 3.14 SqFt, 20GPM/SqFt, 63 GPM "design flow rate"... (Model S-244T if it helps anything)
I added a salt water chlorine generator first thing before even observing it on (other than the pool inspection when I didnt know what I was looking for). It is a Pool Pilot; auto pilot digital.
All PVC piping is 1.5" except the SWG which was 2" from factory so I had to neck up and back down to accommodate it. Here's a picture of the set up before and after if it helps.Attachment 32138Attachment 32139 .
Notice I had to use several additional small bends to get it to line up and the rise on the cell orientation no doubt added resistance. Not sure if any of this hurt my cause.
With all that pertinent information out of the way, the problem: When the 3 way valve is open to both main drain and skimmer, this problem doesnt exist, but when I shut it to only suck from skimmer and start vacuuming, I lose flow gradually over the course of about 10 minutes. The pressure on my gage never rises, rather drops as the flow reduces. I can prolong this from happening by unscrewing the jet eyeball thing while vacuuming. Once the flow stops though, I have to stop, got shut the pump off, and wait a minute. After turning it back on it seems to have regained its flow, i reattach the skimmer plate and continue to vacuum for another ten min until I repeat the cycle over again.
When it does this there is still no additional air (i've fixed all suction air leaks I think, and have a constant small bubble in the top part of the lid where the handle is. Seems like its just trapped up there at the high side.).. So its full of water, but it seems like the impeller is just spinning in the water and i guess just not having 'traction'. I can't hear any cavitation but I may wouldnt since the pump isnt all that quiet in the first place.
Things I've done to try to help this inside the pump is replacing the o-ring on lid, assuring impeller is clean, I noticed the previous owner stripped out the inserts holding the diffuser in place so I retapped those and have the diffuser held firmly in place now with 1/4"-20 stainless screws. The o-ring on the nose of the diffuser has not been replaced and doesn't look great. Pool store says that if that was the cause it wouldn't slowly degrade, it would just never prime. The impeller has a few stress lines, but not any breaks or large cracks that I can see.
So in short, I'm baffled by why the flow would just stop like that while pressure decreases. The filter does not require a backwash to get it going again either. I've never seen pressure go up on the filter the 10 PSI that everyone says should be my indicator to backwash actually, in any valve setting. It just sits around 12 PSI at all times.
So, I know that was a really long post and sorry about that, but any help or advise will be greatly appreciated. Thanks so much in advance!