FC 5
TC 5
Ph 7.5
CYA 30
CH 240
TA 30

Above results were taken last week and I am very happy with them and my pool. The one result which is a bit odd is the TA which is low. Having said that the Ph has been 7.5 for sometime now and does not fluctuate at all.

Question is it ok to leave it at 30 or do I risk some problems further down the road. When it was in range last which was over the cooler winter months I was adding about .5 ltr of acid a week but have not done so for about 6 weeks now since we started using the pool daily with the hotter summer months.

Now that summer is here it needs regular topping up and my fill water is also TA of 30.

All your thoughts would as always be welcome.

Cheers

Have you calculated CSI for those numbers, and what is water temp? I'm not as familiar with fiberglass pools and if they have the same concerns as plaster ones chemically. Hopefully someone else here can answer.

30 is a bit low, I would raise it to about 50. Don't worry if the pH goes up a bit. As long as the pH is not above 7.8, I would not lower it. You should also raise the cyanuric acid to about 50 ppm.

For me, this is another case of NOT fixing something that isn't broken. While this pool falls outside of our normally suggested guidelines, the OP apparently has a troublefree pool with clear water and needing nothing. I would be reluctant to change that.

TA of 30 is certainly quite low and there is the possibility that the pH might be unstable but, so far, OP reports pH is just the opposite......quite stable. I would leave it.

The one thing we do not know about is chlorine consumption. It is probably exceeding 2ppm daily and increasing CYA to around 50 would certainly reduce consumption

Thanks for input guys, will increase CYA as suggested and continue to monitor Ph for any fluctuations.

With your TA so low, you might want to look for liquid stabilizer instead of cyanuric acid. Adding anything acidic could cause your pH to drop too low.

Or, increase the TA and pH a bit before adding the CYA.

Specifically, if 20 ppm CYA were added with your numbers (especially the low 30 ppm TA), the pH could get down to 7.0 unless there was carbon dioxide outgassing. So just be aware of that and raise the pH as needed if you add the CYA. Raising the pH in advance won't help you much since even raising it to 8.0 would still have the pH drop to around 7.1. If you use 2 pounds of pure CYA to raise it 20 ppm in your 12,000 gallon pool, then you'll need about 2.5 pounds (roughly 1/2 box) of 20 Mule Team Borax to raise the pH back up to 7.5. As James noted, you could use Natural Chemistry® Instant Pool Water Conditioner™ which is close to pH neutral and mixes almost immediately though it is about twice as expensive.

I'm with Dave (duraleigh), I wouldn't mess with anything. If you have stable pH and you're not having problem with chlorine loss due to sunlight why upset your balance.

However, if you're a tinkerer and want to by all means. Since things are pretty stable now, there isn't any urgency to making the changes, you could make adjustments gradually. Perhaps use Trichlor Tabs or DiChlor for chlorine for a little while. It'll add chlorine, CYA and lower your pH. Then make your regular adjustment to pH as you would normally with Borax. You'll get your CYA where you want eventually, but should be able to better monitor the pH shift and get a little Borates and TA added to the water. After than, you can still use baking soda to get your TA the rest of the way there if you wanted to.

If you kept that current balance your Saturation Index would be in the negatives (acidic water) and destroy your fiberglass pool over some months maybe a year. Cobalt is used to manufacture a fiberglass pool, the Acidic water would slowly break this down and release it into the pool to react with chlorine. This makes a very pretty blue and purple material and staining in the pool.

Acidic water is never good for any type of pool. You should always aim for the ideal ranges.

I think I may be missing something, PH determines the acidity of the water and CSI determines how likely it is to form scale or precipitate calcium (calcite) out of the plaster, damaging it. PH drives the CSI. I guess my concern is with the statement saying "Saturation Index would be in the negatives (acidic water)." I run my CSI in the negative numbers without acidic water.

From what I understand PH less than 7 is consider acidic. I believe the recommendations for PH are between 7.2-7.8 for pools.

While the saturation index is clearly relevant to plaster pools, it's not as clear as to how important it is for fiberglass pools. The gelcoat that is put over fiberglass contains filler that is often calcium carbonate. So to be conservative, we usually give similar recommendations for fiberglass as we do for plaster. It is vinyl pools where we generally say that saturating with calcium carbonate is not important (though there has been discussion about that as well). Realistically, with the water cold any rate of deterioration would be much slower.

I was reading my TA test results lower than they were when I first started to test. I would stop the test when the color changed from green to pink and consider that the number. But the directions say to stop adding drops when the color no longer changes from the last drop and not to count that last drop. My color goes from green to pink to bright pink and then to glowing bright pink. I was measuring 20 points lower than what my real TA was.