Low pH and TA, High CYA

[Gm0ney]

My friend just bought a house with a pool that's 5 years old. 16,000 gal, inground vinyl, sand filter, solar + gas heat.

The previous owners were apparently only using Aqua Foot tabs (trichlor + zinc). There are no other chemical pails lying around for TA/CH/PH etc., so I guess they never measured or tried to adjust those.

So, I went over and tested the pool with my TF-100 for him and here are the results:

PH < 6.8 - It was a shade of yellow/orange paler than anything on the Taylor scale.
FC 0.5
CC 0.0
TC 0.5
TA 0 (I think - just turned pink when I added the R-0008 and no amount of R-0009 was changing the colour...never seen that before!)
CH Low (I was kinda reeling from the TA test and didn't get a good read. I didn't have to add many drops. The water in the vial after the test appeared to have a lot of tiny particles in it).
CYA 100+ (I'm going to have to do the diluted test to get a better read - but it's higher than anything I've ever seen in my (BBB) pool).

So what's the first step? The order of battle? Bring up TA and then bring up PH? Is there some way to do both or is it one then the other? Should he be trying to swap out some water first to bring down CYA? If he could do a 25% swap now and then another 25% at shutdown in a couple of weeks (it's almost closing time here) then he'll be in a bit better shape next spring.

I'm trying to talk him into BBB...he seems a little skeptical about it though. I was telling him that I was seeing test results that were like nothing I'd ever experienced (I've been BBB from the start 2.5 years ago with our pool) and his water is way out of whack. lol...he just moved in and has a million other things on his plate and I'm all obsessed with his pool chemistry

Anyway, any advice from folks who've seen this kind of chemistry before would be welcome!

 

[jblizzle]

That means the TA is 0 and the pH is down around 4.5. And clearly the CYA is way too high.

If you did not have the high CYA, I would say you should raise the pH with borax which will in turn raise the TA. But, since at least half the water needs replaced to lower the CYA, I think that should be the first step. Then retest after refilling and see where the TA and pH are.

 

[Gm0ney]

Thanks! I'll tell him to start by replacing some water. Probably needs to backwash his filter anyway...

 

[jblizzle]

Don't drain half the pool by backwashing. Any debris will end up on the wrong side of the filter and go into the pool when you run in normal mode.