Thanks aylad and PoolDoc!

I won't try to fix the unbroken system if it remains unbroken...but we've only been operating at this level of Ca++ for a month, and I want to have a plan in case things start to act up.

Quote Originally Posted by PoolDoc View Post
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.
I was hoping that water mixing would be minimized with the shallow end being forty feet (horizontal)ly and eight feet (vertically) away from the deep end drains, and with no water agitation from the return jets. Do you think the "new" water would sink to the deep end level that quickly? (I don't know - tap water is a good 20 F colder than our pool water...maybe its density would be enough to make it sink really quickly. On the other hand, it would have to go around a corner as well.)

I'm certainly not looking for extra work...so I'm glad that it sounds like I can postpone this indefinitely!

Alison