First chemical test of Spa

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That dichlor is good stuff! I've never had my spa so clear that it reflects clouds.
 
Yes, but if you use too much of it, your CYA will get too high and then the chlorine will become less and less effective. Once you reach 30ppm CYA, switch over to your lithium hypochlorite.

Also, assuming you use similar chemicals where you are, pH Down is sodium bisulfate which is a very expensive way to reduce pH as compared to just using muriatic acid. MA is much cheaper to use for pH adjustments and doesn't load your water up with sulfates.
 
I will get some MA. But I already had some PH+ and PH- so I thought I may as well use it up.

Test results from today:

PH - 7.4
CYA - 0
FC - 5 ppm
CC - 0.5 ppm
CH - 75
TA - 125 ppm


I was worried I'm not doing the CYA test properly. So I tested the CYA again today using he standard (50ppm) and got it to match perfectly. So it just seems that the spa has no levels. The water is completely clear still after adding the reagent and mixing.
 
The key to pH stability in a spa is the TA. CO2 outgassing from the aeration is the biggest source of pH rise (FYI, pH Up chemicals typically increase TA a lot). So you want to get your TA down to about 60ppm or less. I don't know if you have borax or boric acid where you are but using borates at 50ppm in your spa can let you drop the TA down to 50ppm and you'll get exceptional pH stability from it.

Just keep using the dichlor. One way to track it is by knowing that every 10ppm FC added by dichlor increases your CYA by 9ppm. So you can add about 30ppm total FC from dichlor and that's about it.
 
So I added 3x PH- today, and got no change in the PH or TA. So I brought muriatic acid, and dosed it according to spa size. Did nothing, so I did it again a few hours later. Still sitting at the same PH and TA. Strange! Is there anything that could counteract the acid to stop it going down? Or does it take a long time to decrease?
 
No, nothing in the tub should prevent acid from lowering OH and TA. What was your PH and TA when you added acid? How much acid did you add? Was the MA 31.45%? Or 15%. No, it doesn't take a long time. It should register in a few minutes with the pump running.


If your PH was showing 8.2 or whatever the highest reading is on your PH test then it is likely that the PH is actually higher than thst and it could take several doses to get the PH down to start reading below 8. Once you get there it should start having a bigger impact on TA also.
 
PH was 7.5, and TA was 150. So nothing crazy high. I've had the jets running, so expected the PH to rise a bit after it was lowered. But I was expecting the TA to lower at least a little.

I don't know the percentage of the acid. They don't like adding those numbers here. I'll have to have another read later and see Oriya in there somewhere. Poolmath said to add 60mls. The acid said to add 50mls based on the spa size. So I've now added 2x 50mls.
 

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150ppm TA for a spa is quite high. The aeration jets plus all that excess carbonate will definitely raise the pH quick. You need to get that TA below 100ppm or else the spa water will always have very high pH. What is your calcium hardness (CH)?
 
High TA + aeration = high pH

It's that simple. Can you run the circulation pump without air jets? That would allow you to mix in the acid and get a better pH read before all the pH can rise from aeration.
 
So the TA is sitting between 100 and 125. It needed just a half drop and it would have been perfect. It's slowly coming down. But needing much more then the label says. I added some more this evening and will test in the morning.

I think I'm getting mixed up with PPM and the measurement we use - mg/L. I think it equals the same or similar, because the label says to use 30-50 mg/L maximum. But look at that warning label. Nice that they don't allow the CYA to get too high. Not that anyone really reads it anyway.

I've put 150mg total of stabilised chlorine in now over the past few days. And poolmath says I should add 177g. So I'll test CYA soon and hopefully I have a reading.

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