For the last 3 years we had what I thought was problem with a DE filter leaking DE back into our in ground liner pool, powder on the bottom all the time & having to run our filter attached vac constantly. Replaced entire guts of hayward de4820 filter (grids and manifold, even though I was unable to find any defect) and eliminated the selector valve and installed a check valve between the pump and filter. Powder problem continued, so i was planning on switching to a cartridge filter after replacing our 12 year old liner this past fall. New liner installed, filled the pool got the water reasonably where it should be and then it was cold so didn't bother with much or any chlorine until opening a few weeks ago- ran the filter and no powder on the bottom, which was weird. Picked up an 80lb cal hypo bucket, added some and the powder was there the next morning. Now I KNOW this HAD to be calcium precipitate rather than DE; did some Googling and sometimes an issue with high PH & alk so got a pool water analysis from Ace Hardware:
Alk w. stabilizer corr 91ppm
Added 1/2 gal muriatic and 2 gal liquid sodium hypochlorite & ran the pump for 2 days, no powder on the bottom since, so I may have the problem solved but I want to use cal hypo and am a little hesitant. My test kit (new reagents) sold by Ace shows PH now around 7.8. the CL on the test kit only goes to 3 but shows off the high side scale with even only one of the 5 drops used for the test- and the ace guys keep telling me to add that sodium hypo, which I did. I've not been back for another test at Ace, but looking for some help as to why my test kit is showing such high chlorine, why even if I skip a few days the test kit does not indicate that the chlorine concentration is coming down, and if I'll be OK and precipitate free using cal hypo with what my numbers would be now?
any help greatly appreciated