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Back on track:
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Quote Originally Posted by PoolDoc View Post
Sorry it's taken me so long to reply.

Assuming: 17k gal, pH: 7.1, TA: 90, CH: 160, CYA: ~20. Location in KY, with moderately cold winter (sub-zero possible, but not likely).

One open question: is the "security cover" mesh or opaque?

Comments:

Your current water is unlikely to scale, but could possibly damage the concrete bottom. However, adding lots of calcium will increase the chance of algae-aided calcium deposits. So . . .

1. Raise your borax to 60 ppm -- 11 boxes of borax. Do NOT add acid at this time. Borax will significantly reduce the chance of algae forming under the cover, and will make it easier to kill the algae if it does form.

2. Target a pH level of 7.8 - 8.0. This will reduce any corrosion of the concrete to vanishingly small levels. The borax addition may be sufficient to raise the pH, or you may go a bit high. But WAIT till it's fully dissolved before attempting to adjust the pH either way.

3. If you are not using the pool, go ahead and install the cover now. If it's a solid cover, leave a corner uncovered so chlorination byproduct gases do not accumulate.

4. Use bleach to raise the chlorine levels UNDER the cover, and eradicate any remaining algae.

5. Test chlorine & pH, but don't bother with other tests until the pH is back in range.

6. Report back once the borax is up, the cover is on, the pH tested, and the algae is gone.