Hi Shaggy;

Watermom asked me to take a look at your post -- she's right, it reads like you've been drinking a lot of the pool industry koolade, whether you are in the biz or not.

Several important points:
  1. Low pH will damage copper pool heaters; low hardness does not.
  2. Hardness -- at ANY level -- is only an issue in a 'plastic' pool (PVC pipes, vinyl liner, polymer pump) if it's HIGH. A hardness of 10 is fine in a plastic pool.

In general, the whole saturation index thing the pool industry has wasted so much paper on, doesn't apply to most pools. It's significant in PLASTER (cement & marble dust) pools, but overblown or inapplicable almost everywhere else. The entire situation is a mess.

If you are a pool owner, the answer is don't worry about it much unless it's too high, or unless you have a plaster pool.

If you are in the pool biz, this is a discussion that belongs in the China Shop.

Best wishes,

PoolDoc