I am at a bit of a loss as to what to do. I've read many, many posts and comments and have tried multiple steps to fix the problem.
15k gallon in ground
48sqft DE filter - new grids last fall, cleaned and backwashed (2 times in last 60 days)
In floor cleaner
Purchased and had professionally installed Ecostar last summer
I drained my pool late April to replace water that was about 4 1/2 years old. Had backwashed filter prior. Filled pool, added some shock, stabilizer, etc, based upon pool store advice. Everything worked good for about 10 days, then I noticed a lot of bees coming to the pool. Searched on the threads and found that if I added Bio-Dex Skillet, bees seemed to not care for the stuff. Well, as I was adding the Bio-Dex, I happened to drop the bottle into the pool and the entire quart or so emptied into the pool. Figuring it was not swimming season quite yet, I figured I would watch the pool. Bees left, water felt good, but was having trouble keeping chlorine stable. Went out of town for a week and came back to a green pool. Pump was not priming. Turned off the auto-prime, added a bunch of shock and fired that baby up. Minimal movement of water into the pool. Not enough pressure to push up in floor heads. The pump did prime, but the pump was not pushing as much water as it should or as was normal. Pressure within the 20-30 range, which is normal for my pool. Up only 5 or so from a freshly backwashed stage. I know normal water flow as I have an aerator and when I turn it on after backwashing, I can validate how far water travels. Anyhow, I figure something is odd and I decide to backwash the pool. I do so, and things start to work again. Two weeks go by, same thing happening. It's not green (as I kept an eye on it) but it is low flow, marginal pressure increase, if much at all. Go to pool store, explain situation, they are kind of at a loss for answers, suggest cleaning and backwashing. Do some research on the forum and find out that excess algaecide should/can be removed by adding extra shock. Backwash, clean grids, add extra shock and start it up again. Flow good. Pressure good. No air leaks, at least that I can see in the leaf basket or pump basket.
So.... I go out of town for a month for work. Provide my oldest daughter with detailed directions. Check daily with aerator to see flow. Check chemicals daily to ensure chlorine is not getting eaten up. 3 weeks in, she says the flow is about 70% of normal, auto priming issues. Guide her through turning off auto-prime. She says things look like they are working. She heads out of town, I come home 3 days later, pool is cloudy again. Pump is primed (no air that I can see) but flow is back to minimal at best and pressure is within the 10 point range of newly backwashed and needing to be backwashed.
Pull grids again, backwash and now it's back to normal. 5 days in, I notice flow is starting to reduce (based upon aerator). Upped the KPH a touch to increase, but it's already starting to diminish.
Any thoughts on what might be next steps? I've talked with the pool store(s) and they walk me through their stuff. Have tried a variety of options listed on the threads. I have checked the impeller and nothing is stuck there. I have increased the pump speed to try and compensate, but that's short term.
At this point, I'm wondering one of two things. One, the Bio-Dex has done something horribly wrong to the water and it's collecting on the DE, making it hard to push water through. Two, something is wrong with the pump/impeller/motor, that as pressure should be building in the pool as dirt, grime catches, the pump cannot keep up. Perhaps it's a combination of the two.
Also, prior to adding the Bio-Dex (after filling) the leaf basket would be about 3/4 full when the pump was on low speed. I was told this was normal (as it was this way all last pool year) and sure enough, when automus-prime turned on, it would fill up quite quickly. As of the recent backwash, I do not see this happening. Cannot recall if it did after the first green incident.
Any and all help is appreciated. I am reasonably astute at reading the forums and trying different things, but am perplexed at this time.