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Water Balance with Borax

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Hi folks,

My local community (Ottawa, Canada) has tap water with a high pH (9.39) and low TA (35.3) (per city reports). The tap pH is too high to measure, but the TA checks out with my Taylor test kit.

My problem is that if I use Muriatic Acid to drop pH to around 7.6 and add Spa Up to raise the TA to around 100-110 then the pH climbs with time and the TA drops with time. This makes water balance frustrating.

From online threads, I understand I could leave the TA low, drop pH with acid and then add borax to buffer. Then perhaps the pH would be more stable, and I wouldn't need to worry about low TA because the borax would be helping.

This is in a 1000 L hot tub. FYI, for sanitizer, I am using 2-part bromine to get started after a refill, floater with bromine pucks, and adding bleach after each soak to reactivate bromine.


1. What TA and pH I should target before adding borax?

2. How much borax should I add? I am using 20 Mule Team 99.5% pure.

3. I like to use the "saturation index" calculator that came in the Taylor test kit to confirm balance. Can I adjust for the borax in the water somehow?

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