CYA high, to dump or not to dump

[dickeystorm]

Hi all,

My cya is high. I'm having trouble getting an accurate read on it but my latest reading shows 100. Last season it was 120 by my reading (but I was even newer at it then). The local pool store tells me it's 40 but my chlorine level was over there equipment max level of 10. Watching the water from last season and this season it seems that I have to keep the chlorine level high to compensate for the high cya so I don't trust the pool store reading. I'm going to try and have them retest tomorrow since my chlorine has dropped to 8 (2.5 drop in one day, is that normal?)

The big question is should I dump and refill? The pool calculator tells me I need to dump 2/3 of the water assuming it's pure (it could happen hehe) I need to test the city water, the pool store tells me there is a lot of metals in the city water, will that be difficult to clean out.

My latest readings are:
FC 8.0
CC 0.5
pH 7.9 (going to add acid)
CH 410
TA 230
CYA 100
copper .13
temp 75

Thanks.

 

[dmanb2b]

I would target getting CYA down to around 70 and try that 1st (about a 1/3 drain/fill), unless water is cheap in your area. Have you tested you city water? Metals can be treated with regular use of sequestrant, but it may not be needed.

 

[JasonLion]

I'd trust your CYA test results over the pool store's. Just remember, if you are using the black dot CYA test, the black dot should completely disappear, no hint that it was ever there. Also, the test is designed to be read in direct sunlight with your back to the sun so the sample tube is shaded by your body.

Getting CYA under 100 will definitely be a big help, well worth some water replacement.

TA and CH are both high, so you also need to keep an eye on your PH. You want to keep your PH below 7.7 at least until you can get TA down somewhat.

 

[dickeystorm]

Thanks for the quick replies. I have not tested the city water yet. I have also been doing the testing indoors in the late afternoon, that's when I can get to it.

I'm leaning toward a major drain/fill since my CH is also high and there are some spots in the plaster that I could patch.

I'll retest tomorrow and compare the pool stores results to mine.

 

[dickeystorm]

I retested my cya after letting the chlorine come down under 10 (FC 8, CC 0). My reading was about 100, my wife got 50 and the pool store got 75. Meanwhile the water looks good, my last FC read was 6 with CC 0. Still not sure if I need to do anything about the cya level. What is the target number? My understanding is 40. Does it change with age, the pool is about 27 years old, plaster.

Thanks.

 

[RobbieH]

Nothing will change with the age of the pool, I'm guessing you mean the required amount of CYA? 40 is a good target.

If you mean will CYA change with age, mostly due to refilling the pool, not because it gets old. My CYA was 70 last year, but 0 now due to reflling after fixing a leak and all the rain we've had.

 

[dmanb2b]

For a non swg pool, 40 would be a great target, but if water is expensive you can get by with 70 and need to use nothing but liquid chlorine to chlorinate from that point on.