Water Balance with Borax

[cmh2]

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.


Questions:


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


2. How much borax should I add for 1000L of water? 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 to keep doing this?

 

[jblizzle]

Have you read: Borates - Why and How

Borates are a bit over-rated at times.

Also, PoolMath with calculate the CSI for you.

 

[cmh2]

Thanks, that is a helpful thread that I had seen but couldn't find again. It is geared towards pools, so if using a hot tub do I also need to do the borax/acid in batches or can I just go for it? PoolMath says I need 353g borax and 175 mL of muriatic acid.

As for why: I want to avoid raising TA this time to avoid problems controlling pH. I thought I would need to compensate with borates. Is this true?

 

[jblizzle]

I would try keeping the TA lower and see if your pH rise slows down before messing with borates.

You could also use boric acid instead of the borax/muriatic acid combo if you go that route.

 

[cmh2]

OK, thanks for your help with this. Intended to target 50 for TA, but brain misfired and I wound up around 80. I will try it there with a pH of 7.6 and see how it creeps up. I'm interested in the borates for water feel too, but will delay that to see if I can get pH and TA to play better together first.