Quote Originally Posted by alisonquilts View Post
I have a SWCG and I am not seeing any scaling problems so far with this Ca++ level, but I would prefer to deal with it and get it down.
Uhm. If it's not broken, why are your trying to fix it? 420 ppm is a number; not a pool. It's your pool that's the issue (or non-issue), not the the number. It doesn't damage your SWCG to scale up. If you clean every 3 months, as may be recommended, and have no problems, well, you have no problems.

If you want a larger margin of safety, why not strip your carbonate alkalinity (hold your pH to near 6.8 and aerate -- covers OFF!), and then re-buffer with borax.


I feel this is the best way for me because of the extreme shallowness of the shallowest part - 9" - and the need to keep a certain depth over the liner at all times. Here's my question: what is the minimum depth of water (and thus weight) required to keep the liner from lifting? 4"? 5"?
I don't know; it depends on things like how wet ground around your pool is.

Also, I don't see any point to draining and filling at the same time. If you want to do an in-place water replacement, you need a membrane (like an oversized winter cover) to separate the old and the new water.