Will I get more alkaline minerals out by draining from skimmer or from main drain?

[Ted_S]

Hi,

In the desert where I live the water is hard and it's necessary to drain your pool every several years. I'm at that point, as my pool just gobbles up acid with nary a swing in pH. Can't do it now though because in the summer the 100+ degree heat would damage the plaster. So I want to drain a little at a time. Maybe I can do this more efficiently if I target either the water near the top -- skimmer -- or bottom -- main drain. Would the calcium and other minerals tend to float upward (seems unlikely but that's only a guess), or to settle to the bottom?

Thanks,

Ted

[PoolDoc]

Dissolved minerals are pretty much equally distributed through out the water, so it won't really matter where you drain from. It does matter how much you drain at a time. For example, if you have a 10,000 gallon pool, and you drain & replace 1,000 gallons 5x, you'll only have replaced 40% of your water, even though you've added 5,000 gallons. The reason is, on each successive partial drain, you drain part old water and part new water.

If you drain 1/3 of your water 3x, you'll replace 70% of your 'bad' water. [ (1-0.33)^3 ]

By the way, you'll be better off if you use muriatic acid instead of "pH Down" or some other form of sodium bisulfate for your acid source.