Ideal CH advice

Gumbalskip

Member
Oct 8, 2016
9
Maryland
Hey all,

According to Taylor, ideal CH is 200-400. PS and PMath lists ideal as 350-550. I’m curious as to why the difference, and could the fact that mine is not in PS ideal range be why I’m seeing scaling...

We had our plaster pool resurfaced 2 years ago. I’m noticing a bright white scale showing up in corners and along the tile line (grout). It is not widespread, fairly intermittent. I assumed it was low CH pulling from the plaster.

Current values:
  • FC 11
  • pH 7.6
  • TA 70
  • CH 310
  • CYA 100 (high, I know)
I have a time getting clear results from my Taylor kit on CH. I most often end up with a blue leaning, purple endpoint. I’ve tried the pre-titrant trick and I still don’t get a complete blue color.

TIA
 

Dirk

Gold Supporter
TFP Guide
Nov 12, 2017
6,191
Central California
If you're not completing the CH test correctly you may have more in your water than you think. And it's high CH that causes the scaling, not low. So that might be your answer. I keep titrating until it is obviously blue. I tend to wait a bit between drops, like a few seconds, to let the color develop fully, so that I don't overshoot the end point.

Have you ever tested your fill water for CH? Is it high there, too? Post that result and others here can help. If you have high CH fill water, you have to start paying attention to CSI. That index can help you keep your pool scale-free.

Mine is, but I still get some of that haze above the water line. I believe that is due to evaporation, not out-of-balance water. But if you've got scale below the water line, that's the water not the sun.
 
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Gumbalskip

Member
Oct 8, 2016
9
Maryland
Im filled with public water from a truck, so I don’t have access to that now. Occasionally top off with well, so I could test that.

the only thing about continuing to add titrant that if I go to far, the color becomes diluted And even more difficult to rea. I’ll keep working on it. Im not sure on the lifespan of the chems in the Taylor kit, I may need to replace them too. We are moving to SWCG this fall and will replace the water so I can start new.

but to my original question, aside from my scaling issue... should I strive for the PS ideal? and not Taylor?
 

Dirk

Gold Supporter
TFP Guide
Nov 12, 2017
6,191
Central California
Absolutely (if by "PS" you mean "Pool School")! You can very safely ignore all advice and theories and numbers other than what you get from here. That'll be your fastest/best MO to resolving just about any issue with your pool.

The original fill water doesn't matter now, as we know what's in your pool (or will, when you figure out the test). What your topping off with is important now. Calcium (the stuff stuck to your walls) does not evaporate. It builds up over time in your pool (every time you add water) and eventually comes out of solution and starts to show up on your pool surfaces. If your fill water is CH=0, then once you get to your target CH, you'll never get any more. But if your fill water has any CH, and especially if it has a lot (like mine does) then your CH will build up in your water and you'll have to eventually deal with it (by draining) and by scraping your surfaces if you ignore it. So that's why I asked about the CH of your fill water, I meant the water you're currently adding to your pool.

When you next post your results, include CSI, and include a suite of results for your fill water. That'll help the experts here advise you on your best course of action going forward.