Cya Level Has Risen?

[bart6453]

So I checked my CYA level yesterday and it was at about 70ppm....but 2 months ago I checked it and it was at 40ppm...so I switched to bleach. What could be adding CYA???

[chem geek]

So I checked my CYA level yesterday and it was at about 70ppm....but 2 months ago I checked it and it was at 40ppm...so I switched to bleach. What could be adding CYA???

When did you switch to bleach -- 2 months ago? If so, then there should not have been any increase in CYA during that time. Dichlor adds to CYA, but bleach does not (for every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm). It may have been a test error -- perhaps the temperature was very different between the two times you made a measurement. Are you using test strips or the turbidimetric test as in the Taylor K-2006 or the TF100?

[bart6453]

So I checked my CYA level yesterday and it was at about 70ppm....but 2 months ago I checked it and it was at 40ppm...so I switched to bleach. What could be adding CYA???

When did you switch to bleach -- 2 months ago? If so, then there should not have been any increase in CYA during that time. Dichlor adds to CYA, but bleach does not (for every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm). It may have been a test error -- perhaps the temperature was very different between the two times you made a measurement. Are you using test strips or the turbidimetric test as in the Taylor K-2006 or the TF100?

That is exactly what I was thinking.....must have been a test error.

I am using the Talor turbidimetric test.

could have been a temperature issue.....strange.

I think I might just dump the water as it is getting a bit old. So to get the CYA to 20 or so .... I would simply add dichlor until it's sum total was 22.2 PPM FC added...then I would have 20ppm CYA??? Should a guy run the CYA at 20ppm or 30ppm???

On another note...could my high CYA be the cause of it being hard to get the FC to break point when I shock it??? I usually bring it up to 15ppm FC to shock...but if my CYA is really around 70ppm...that could be too low of a shock amount... right? (Since I most likely had a test error...who knows which one was in error, the first or the last)

[chem geek]

Yes, just use Dichlor for a while -- I'd get up to around 30 ppm CYA so around 33 ppm FC cumulatively added of Dichlor and then switch to bleach. 20 vs 30 ppm CYA isn't a big deal, but with more experience from users it looks like 30 ppm CYA is fine. As for oxidizing bather waste, 70 ppm CYA at the same FC level would take longer, but I wouldn't think it so long as to be a problem. Have you noticed Combined Chlorine (CC) lasting longer than an hour or so?

Don't worry about the shocking not achieving breakpoint. There isn't a magic number like that -- breakpoint refers to having water already with ammonia in it and adding chlorine. In a spa, you've got the opposite situation where chlorine is already there and then bather load (sweat/urine) gets into the water. Perhaps if you don't have chlorine when you soak then you are adding chlorine after the soak, but if you are adding enough daily then it will be enough to handle the bather load and last until the next day. There normally wouldn't be any need for regular shocking if you add sufficient chlorine daily (or before/after each soak).

All that shocking weekly does is (hopefully) "catch up" if you are behind in not using enough chlorine or it "accelerates" the oxidation of anything that is slower to oxidize.

[bart6453]

Yes, just use Dichlor for a while -- I'd get up to around 30 ppm CYA so around 33 ppm FC cumulatively added of Dichlor and then switch to bleach. 20 vs 30 ppm CYA isn't a big deal, but with more experience from users it looks like 30 ppm CYA is fine. As for oxidizing bather waste, 70 ppm CYA at the same FC level would take longer, but I wouldn't think it so long as to be a problem. Have you noticed Combined Chlorine (CC) lasting longer than an hour or so?

Don't worry about the shocking not achieving breakpoint. There isn't a magic number like that -- breakpoint refers to having water already with ammonia in it and adding chlorine. In a spa, you've got the opposite situation where chlorine is already there and then bather load (sweat/urine) gets into the water. Perhaps if you don't have chlorine when you soak then you are adding chlorine after the soak, but if you are adding enough daily then it will be enough to handle the bather load and last until the next day. There normally wouldn't be any need for regular shocking if you add sufficient chlorine daily (or before/after each soak).

All that shocking weekly does is (hopefully) "catch up" if you are behind in not using enough chlorine or it "accelerates" the oxidation of anything that is slower to oxidize.

my combined chlorine has a tendency to stay high most of the time. It seems to hover between 1-2ppm at all times no matter the bather load or the shocking procedure.

That's good information about the shocking.....I typically add chlorine every other day, keeping it above 2ppm FC and below 5ppm FC. I also add a bit of chlorine after a soak with just the wife and I. If there is a party, I add a bit of MPS and make sure the FC is at 6ppm....then add some more chlorine before wrapping up the party. In the AM I check it and am typically at 2ppm FC, so then I will shock it and call it a weekend.

I have been shocking every week...sounds like I can skip that if my chlorine levels are kept proper.

[chem geek]

Just so you know, MPS will register as Combined Chlorine (CC) in the chlorine test unless you use an interference remover. However, I wouldn't expect it to last more than a day or so if there is bather load. So I'm not sure what the "persistent" CC is that you have if it's not the MPS.