How much chlorine should my pool be using?

[DistantHorizon]

The saga continues! On a positive note, the pool store took back their silly Phos Free, so that's $40 back in my pocket.

Went to another pool store where CYA scored a 70! Apparently I can get whatever numbers I'd like just by getting different people to test, lol! Chlorine had dropped a whole ppm, from 8 @ 9am to 7 @1:30pm, part of which I might write off to testing inaccuracies.

I guess irregardless, my pool IS running fairly well. I seem to lose a lot of water to evap, and it seems to get a lot of dirt in it; but water has been clear for IIRC, a couple weeks now.

Don't panic. Your CYA test is more likely to be accurate than their dipstick-in-tube test. The disappearing black dot test is the only one we trust.

So, if you are getting 45ish for your CYA reading, assume that is correct. What goal are you shooting for? Typically we suggest 40-50. if that is what your target is then remove all pucks from your pool and also don't use any more dichlor. A week after the last dose of any stabilized chlorine, test your CYA again, but not before. Then, post a full set of numbers here and we'll make a recommendation for you from that point.

I don't know what I should be shooting for. I figure I can shoot for 45-50 or 70ish, but I don't know which. I am uncertain of which will be cheapest. I wouldn't mind running higher levels, but it seems that shocking would be fairly expensive and hard on swimsuits.

I will not add any more CYA (though I lost a little this morning to a fairly long backflush) for another week, and I'll post numbers with my brand new CYA reagent bottle.

[Watermom]

Losing 1ppm if it was really sunny wouldn't be unusual. You're gonna lose chlorine and that is fine. CYA helps protect it but losing it during the day is to be expected. Plus, as the chlorine does its job of sanitizing the water, it is also depleted.

If our CYA is 45ish, I'd leave it there for now. If you find that you can't keep chlorine in the pool, you can always add more. Don't bother having anyone else test it for you. YOU will do a better job than any pool store. As far as having to shock harder --- you use more chlorine at a time but don't have to add it as often so it balances out. And, high chlorine with high CYA is not any harder on swimsuits than low chlorine and low CYA. It is the same.

[DistantHorizon]

Jun 25 morning, FC 8, pH 7.4
Jun 25 evening, FC 7

Jun 26 morning, FC 6, pH 7.2, TA 110
Jun 26 evening, FC 5+ (didn't bother to dilute), pH 7.2

Jun 27 evening, FC 5, pH 7.2; added 52oz 6% bleach for target FC 6
Jun 28 evening, FC 5, pH 7.3/7.4; added 52oz 6% bleach for target FC 6

On Jun 29, I received my FAS/DPD test kit! Also new CYA reagent, but it hasn't been a full week since adding stabilized chlorine.

Jun 29 evening, FC 5.5, pH 7.6, CC maybe .5; added 2.5oz cal hypo for target FC 6/6.1

Jun 30 evening, FC 4.5, pH 7.4, TA 110; added 7oz cal hypo for target FC 6.1.

Since I've been uncertain about CYA, I made the decision for now to just try to keep FC between 5 and 6, since 5 is above the minimum on the the 60-90 range of the Best Guess chart.

What do you all think about these numbers? I guess the only thing I notice in looking over them is that FC dropped quickly again from Jun 29- Jun 30... but I'm thinking maybe the Pool Calculator's 2.5oz recommendation was a little low.

Thanks again for all the help.

[Watermom]

Your numbers look fine. Post your CYA level when you test for it.

[DistantHorizon]

Well, in the last week or so, I've been very busy and also had the pump motor quit midway through the holiday weekend, so my chlorine numbers have been irrelevant and jumped all over the board (I kept it high with liquid bleach during the few days where it wasn't circulating); but I tested my CYA just now, and I'm sticking to my guns - it's around 45 or so, about like it tested with my old reagent.

Have been doing my best to keep chlorine at 5 or above for a while now, but it looks like I can back that down to 3+ since I'm more confident CYA is at MY test results, and not the pool stores.

I noticed the Best Guess Chlorine Chart has blank areas - nothing between 20-30, 50-60, and 90-100... I assume those are just subjective gray areas?

Not sure whether to run CYA up higher or not - it sounds like the amount of sun I get would support higher CYA, but then when I shock people can't swim for a while. I'd hate to be the guy whose pool wasted a bunch of swimsuits in one day.

[Watermom]

Stay with CYA of 45 for awhile and see how it goes. When you test in the evenings, add enough bleach to take the cl back up to around 6. See if you stay above 3 by the time you test the next evening. If you consistently find that you can't, take it up to 7. If that still doesn't keep you at a minimum of 3 by the next evening, then at that time, you can decide that you may want to bump the CYA up a little.

BTW -- High CYA/High Chlorine is no more damaging to swimsuits than Low CYA/Low Chlorine.

Actually the chart shows 10-20, 30-50, 60-90, 100-200

[DistantHorizon]

Actually the chart shows 10-20, 30-50, 60-90, 100-200

That's what I mean... say you have CYA 55, the chart doesn't have a recommendation for it... so I figured those were areas where you just have to see what happens with your specific pool, deciding whether to follow the higher or the lower recommendation.