Stay the new course?

[SeanW]

We have a 9 year-old, 18,000 gal, in-ground, concrete/plaster pool in the High Desert of CA that I took over the full maintenance of in June. Previously a variety of "Pool Guys" used tri-chlor tabs and who knows what else to keep the water clear and reasonably algae free. It was drained two years ago for what I understand now must have been high CYA levels (at the time I think it was explained to me as "chemical levels so high that adding more chemicals does no good"!?!).

I did my homework prior to joining PoolForum by reading just about everything on PoolSolutions. I have pulled out the tri-chlor and now use only LC for sanitation.

Here are my most recent numbers:

ph: 8.0
TA: 135
CH: 390
CYA: 100

The CYA is slowly dropping and I have been using muriatic acid to try and keep the pH below 8. I've had the chlorine as high as 3 but it has been a struggle to get it any higher. The water is clear and any algae that appears is easily brushed away.

Should I just continue to try and keep the pH down and the chlorine up or is there something I am missing here?

Thanks again for all of the great info and advice.

[PoolDoc]

Here are my most recent numbers:
ph: 8.0
TA: 135
CH: 390
CYA: 100

The CYA is slowly dropping and I have been using muriatic acid to try and keep the pH below 8. I've had the chlorine as high as 3 but it has been a struggle to get it any higher.

Should I just continue to try and keep the pH down and the chlorine up or is there something I am missing here?


It's very odd that you cannot achieve a chlorine level higher than 3 ppm. How are you testing?

Also, your saturation index (pH + temp + TA + CH) is too high, assuming you are testing accurately. In your area, you are running a real risk of hard-to-remove scale forming in various places, so lower the pH, at least to 7.6.

Besides telling us how you are testing, do this:

1. Buy a gallon of 31% muriatic acid to your pool. Add it, 1/2 gallon per dose. Wait a day, and retest the pH, to make sure nothing surprising happens. There's a link in my blue signature block to a page explaining how to use muriatic acid; read it! Make sure the pump is running when you do so; leave it on for an hour after.

2. Buy 3 gallons of PLAIN 8.25% household bleach. Add them all at the same time. (If you also add muriatic it acid, do so in a DIFFERENT area of the pool. You can add the acid in the deep end, and the bleach in the shallow end.) Make sure the pump is running when you do so; leave it on for an hour after. Test the chlorine level that evening, and again in the AM. The result should be well over 3 ppm, and should be virtually the same in the AM.

[SeanW]

Sounds like I am on the right course, just not using the right quantities.

I bought a Taylor K-1005 kit before I found this forum. I figured I would need a K-1515 if I ever get the chlorine over 5ppm.

We have a solar heater and I have it set to max out at 83 when we like to swim in the late afternoon.

I have been using 31% MA but never added more than 1/3 gal at a time. That was the first and only time I reached 7.6 pH. Since then I've only used small amounts to keep the pH just below 8.0. I'll start adding more to get to 7.6.

I have been using 12.5% LC from my local pool store but again I don't think I've ever added more than 1/2 gal at a time. I've followed the advice to add in the evening; I'll start adding more and keep a close eye on the ppm level.

[PoolDoc]

I bought a Taylor K-1005 kit before I found this forum. I figured I would need a K-1515 if I ever get the chlorine over 5ppm.

To manage your pool, you need BOTH the FAS-DPD test AND the CYA test. Your high CYA *requires* higher chlorine levels -- read the Best Guess page page, linked in my signature.