Total alkalinity crept up and now my pH won't sit still

Started by Earl Simmons · · 2 replies
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#1
Been running trichlor and a weekly shock same as always for 30 years and never had this happen before. Tested Sunday and total alkalinity was up around 160, pH was 7.9 the next morning even though I dosed it down Saturday. Add acid, holds a day, climbs right back. Only thing different is I switched shock brands a couple months back, don't know if that's even related.

I know trichlor usually pulls pH down a hair over time not up, so this has me scratching my head. Anybody dealt with alkalinity creeping like this on an otherwise boring old routine. Not ready to go dump water out over it if there's a simpler fix I'm missing.

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#2
Switching shock brands is the detail that jumps out at me, some of those "shock" products are really just buffered dichlor or have soda ash type stuff mixed in to keep it from crashing pH on contact, that'll walk your TA up slow without you noticing. My own pool sits around 90-100 TA most of the year and I don't touch it, just runs steady. 160 with pH bouncing back to 7.9 overnight sounds like your total alkalinity is buffering way harder than it should for how much acid you're throwing at it. Not solving it for you but I'd go read the actual label on that new shock before anything else.
#3
Yeah the label check is the right move before anything else, some non-chlorine shocks do carry a buffer that'll push TA up slow. Mine's plain liquid chlorine for shocking so I don't hit that problem, but if the new stuff has anything like sodium carbonate in the mix that'd explain both the TA and the pH bounce back overnight.