New Home! First time pool owner in the NE (RI)

[PoolDoc]

What is the pH level?

Low pH can keep copper in solution, in spite of high copper levels. But, I've occasionally seen low pH with high alkalinity occur as a possible cause of greenish clear water.

Also, it would be good to test your sand filter. If you really have a 75 gpm pump, you may have blown a lot of your filter's sand out, during backwashes. One way to check is add a quart or so of DE powder to the skimmer with the pump running. If it blows back into the pool, via the returns . . . your filter needs service, and your pump may need downsizing. If it STAYS in the filter, it will help remove algae particles, and may help remove copper or iron, but will cause the filter to stop up more quickly.

[Bassist286]

I'll run a full test suite tonight and report the numbers. I haven't tested my TA and pH in about 5 days. 75 gmp does sound wrong - I'll double check.

[Bassist286]

Just tested everything again. We had a ton of rain over the past week so I expected the water balance to be off. Also did the overnight chlorine test. It passed (9.5 ppm FC last night, 9.5 in the am and 0.5 cc). Water is still a slightly greenish tint but clear.

FC-9.5 ppm
CC - 0.5 ppm
pH - 7.0 (added 4lbs of Borax just now)
TA - 110
CH - 150 (rain must have lowered this. ) Gonna add Calcium if pH is over 7.6 or higher when I get back from work.

Any other ideas on the slight green tint? Haven't testing the filter yet with DE. Pump says noting about GPM, no idea where I got that number.

[PoolDoc]

I would suggest waiting a week or two, before worrying about the color. For reasons I don't fully understand, pools can open green and clear, but then turn blue after a week or so. Iron can do that, but I haven't always seen the characteristic rust colored backwash that would be expected.

Do NOT add calcium when the pH is higher; it is MUCH better to do so when it's low. However, I should ask, why do you need to add calcium? It's ONLY needed on inground concrete pools -- is that what you have? Even then, once your pH goes up, your TA will rise as well. With values of pH=7.6; TA=120; CH=150, your water is plenty close enough to 'perfectly balanced'.

BUT, if you do add calcium, never add a complete dose at one time. Multiple small doses are much, much less likely to result in your pool looking like milk!

[Bassist286]

The Pool calculator shows CH minimum to be 2501 Is that wrong? If i'm at 150- it would seem , according to the calculator, that I have a good amount to go. I think I might have missed something.

[Watermom]

By any chance, is the 2501 in your post above supposed to have been 250! instead?

[PoolDoc]

The PoolCalculator site says a number of things, not all of which agree with each other. It is a very useful tool -- if you know what you are doing. And, being based on Chem_Geek's analytical studies of pool chemistry, it's rather precise.

As it happened, I used the PoolCalculator site to run your numbers quickly, before I posted above.

But, the really important factor for you is, if your have a reasonable pH level (> 7.2) and *some* carbonate alkalinity and calcium present, any corrosion that does occur will take place very, very slowly. I've worked on a large indoor pool (> 150,000 gallons) that had not been drained for 10+ years, and had been serviced only with sodium hypochlorite and hand fed muriatic acid (= small amounts). PH levels on that pool ran a bit high (~7.8), but alkalinity and calcium ran a bit low (< 150 for each), even after 10 years of 'corroding' the plaster. The plaster itself was over 30 years old, and was stained, but not rough.

Keep in mind: to the best of my knowledge, NONE of the saturation indices have been validated by actual lab or field studies, as accurately reflecting the tendency of various waters to corrode or dissolve plaster.

Chasing numbers, whether it's done using Taylor's Dial-An-Index, the PoolCalculator, or with some other tool results in over-controlling your pool's chemistry, which translates into spending time and money unnecessarily.

Keep your pH up, and keep your TA and CH above 100, and you'll be fine. (Well, maybe not. Plaster quality may have deteriorated over the last 2 decades. This is a huge debate, with no final answers. Check out http://poolhelp.com/ for more info. But if you do have plaster problems, but have kept the numbers I indicated (pH>7.2; TA&CH>100), water chemistry is not the cause.)

[Bassist286]

I Guess I’m being a little bit of a perfectionist and guilty of number chasing. The simple pH>7.2; TA&CH>100 are a great benchmark to know. Thanks for all of your help.

I believe I have discovered that the stains on the pool are organic. It appears to be very dead algae. It is stuck on all of the fiberglass walls and some spots on the plaster. I brushed the walls twice and could still make a line on it with just my finger. Any recommendations for a good scrubbing tool? My plan is to get in the pool with a box magic erasers and go to town. I’m not afraid of a little (or a lot!) of sweat equity.
I imagine once the sides are physically clean the water will be perfectly blue/clear.

And Poolmom - yes it was a typo (250).

-Cheers!