Followed treatments, over chlorinated spa

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1,284 litre hot tub. Got an 11ppm free chlorine reading (fine for a spa) and a total chlorine reading of 25. The app recommended putting a LOT of calcium hypochlorite in. I thought it was odd but figured it must know what it’s doing. My spa is now full of extra strong bleach with readings off the chart and I really hope it hasn’t damaged it. Now having to drain it, and refill it with cold water which is going to cost me.

Did I do something wrong or does the app have a bug?

Formula set to Chlorine (calc-hypo), custom chlorine max level of 11, everything else default.

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So, the app will try to calculate “breakpoint chlorination” if the combined chlorine is above the max range.

In your case, the combined chlorine (total - free) is 14ppm, which is the highest I’ve ever seen, and possibly a bad reading?

If that TC reading was correct, you breakpoint would be over 100ppm, which is absurd.

I’ll put a guard in the shock calculators to not allow breakpoint targets over 20 (which is still :banana: s), gimme a few minutes…

But, in this case, how did you take this total chlorine reading?

3

Ok, I made the change to all of the official formulas, so the app will guard against irregular total chlorine levels.

https://app.pooldash.com/formula/vast_argument_756/edit#t-calc_hypo

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As another change, perhaps we should auto-select a formula for spas (vs pools) if your volume is below a certain amount… I’ll put some thought into this as well.

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I used a 6-in-1 test strip and it showed 25-50ppm for total chlorine and 5-11 for free chlorine.

I took a second reading to be sure.

Must be something odd going on, perhaps the pipes are full of biofilm… (I just bought the house with the pool and spa)

1 Like
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Congrats on the house / spa!

It can be frustrating to start up a system that’s been neglected for a while, but then it’s easier to maintain afterwards.

Thanks for posting your experience with the app here, it’s already made the product better for everyone (current and future users).

I also wonder if I should add some additional messaging that “your readings are way out of range”? I thought that the sliders having a certain range would indicate the normal values, but maybe I could be more direct with that messaging…