Quote Originally Posted by howbout
Well, that test was done back on the 18th. Like I said, since then we have treated the pool. At the time we did have algae. So those numbers really aren't anything you can work with NOW. The pool has been shocked,the pH brought up, etc. I think now from my tests and the way it looks everything is in shape. And don't forget it is NOT a vinyl pool, it is an inground pool!
OK, but NOTHING you have done will lower your CYA--if you shocked with DI-Chlor or Tri-chlor it could go up. T/A will go up if you raise pH, and down if you lower it further.

Inground pools can be plaster, tile, concrete, gunite, fiberglass, or, yes, vinyl. Lots and LOTS of I/Gs have been vinyl for well over 35 years now (as a 15 year old kid I took care of a neighbor/friends's I/G--vinyl lined.)

So, ASSUMING you have concrete/plaster/tile, you absolutely must keep your T/A between 90 and 125--80 and 130 should be your trigger points to act. You must also keep your calcium hardness between 200 and 400 ppm--no lower or the water will leach calcium from the walls, no higher or you'll have scaling.

Keeping with that assumption, you have lost flexibility re: T/A and Calcium, but you gain it in pH. Where going below 6.9 is very dangerous in vinyl, you are much safer and could go down lower without fear (but I wouldn't because the water would be too acid). In an algae situation, you can safely raise chlorine levels FAR beyond the shock level for you CYA without fear of damaging or bleaching your liner--levels of 50 or 60ppm which would bleach a liner are not a problem. Also, muriatic acid poured into the water is less likely to damage the walls if it gets close to them. Muriatic will cause a vinyl liner to curl, soften and melt if too much actually contacts it--Muriatic Acid is best diluted and added to the deepest part of vinyl pools, slowly, so it can dissapate and not form a "slug".

New plaster/tile/concrete/gunite pools tend to go through a curing period. During this time your pH will keep rising and you'll be adding Muriatic all the time. This is normal.

Good luck with it.