Use Baking Soda or Soda Ash?

[Shocking]

Newbie. Have been handed a community pool in mechanical and chemical disarray, and I'm trying to recover the situation while keeping the pool open.

When I stepped into the crisis, FC was ~ 0.5ppm. Turns out the trichlor feeder lid was jammed so nobody put any in. Fixed the lid and threw in some sticks. This is where things stand:

50,000gal in-ground plaster. Sand filter.
Equipment ancient and undersized, turnover estimate = 12 hr.
Bucket tests show leaking ~1,000-2,000 gallons per day.
Miraculously, water is currently clear.

FC 4.6ppm
CC ~0
pH < 7.0, i.e., off scale low
TA 50ppm
CH 40ppm
CYA 40ppm

Now that there is at least some chlorine in the pool, I'm taking the next step, which I understand is to bring TA back into range. And that begs the question: do I simply try to bring up TA with Baking Soda? If so, I hear that I'd do well to bring it up 10 ppm per day for 5 days. OR do I use Soda Ash to simultaneously attempt to recover pH? If so, how do I calculate Soda Ash affect on TA? All resources I find indicate only how to calculcate its impact on pH.

This is an albatross, but on the other hand it's an interesting test of technique. Beyond the Baking Soda / Soda Ash question, I'm all ears if anybody has any other advice!

Have benefitted from many threads on this forum! Thanks!!

 

[JasonLion]

Welcome to TFP!

TA is good enough for the moment. I would adjust the PH, retest the TA to see where it ended up, and finally raise TA as/if needed.

 

[Richard320]

Welcome!

You DO realize that the trichlor sticks are what's lowering pH, don't you?
Well, you will when you start playing with http://www.poolcalculator.com/

Enter the pool volume up at the top and then scroll waaaaay down until you see Effects of Adding Chemicals. That will show you how much baking soda doesn't affect pH and what the Soda Ash will do to the pH and TA. And you can also see what the trichlor does to the pool chemistry.

 

[Shocking]

Yes, I am generally aware of the CYA issue with trichlor. I've been told that I might use trichlor in the feeder, and then add cal-hypo in the pool. But I haven't attempted this yet. Not sure how exactly, but I guess I'd throttle down the feeder a bit and add cal-hypo to reach target FC. Any other ideas?

I'd seen the calculator, but not the bit at the bottom. Very cool. Tells me I can correct pH (7.0->7.5) with Soda Ash, and get a 16ppm TA boost while I'm at it. I'll do that tonight.

Thanks!!

 

[Shocking]

Just saying thanks. I'm in a sharp part of the learning curve, and ya'lls advice kept me on track.

Following JasonLion's advice, I adjusted pH using Soda Ash. Took two attempts, but the result was pH up from <7.0 to 7.4, and TA up 20 from 50 to 70. Now I see that, like you said, I can now opt to focus on TA with Baking Soda.

More to Richard320's point, I see that in the abandoned supply room for the pool there are sacks of Soda Ash, presumably to combat the acidity of the Trichlor used in the feeder. Apparently I will have to keep throwing Soda Ash at this situation -- with TA climbing ever higher -- unless I do something different with the chlorine plan.

If anyone can explain a way out of the Soda-Ash-induced dilemma of ever-climbing TA, I'd be grateful. Otherwise I'm planning to attempt use of Cal-Hypo to take some of the sanitizing load, partly to address Trichlor acidity and partly to address the low CH.

Again, thanks!!

 

[chem geek]

You can use 20 Mule Team Borax to raise the pH with an effect on TA that roughly balances the drop in TA from Trichlor. The more exact opposite to a pure acid would be lye / caustic soda, but that's not readily available nor easy to store (it's very hygroscopic). You could also try increasing aeration of the water to raise the pH. Note that when using Trichlor, one normally targets a higher TA so that such outgassing occurs more in which case the pH may be more stable and the use of pH Up will balance the pH and TA better.