Need help...still cloudy after more than a week...very hard water

[PoolDoc]

If this --- CH: 750 => 425 --- is accurate, your filter is doing a heck of a job removing suspended calcium particles. You can test it with the DE test: http://pool9.net/de-test/

Retest your pH with 1/2 pool water and 1/2 distilled water (gallon jug from Walmart: MUST be "distilled"). Distilled water changes the pH very little, but reduces the chlorine by 1/2, so you can get valid results.

However it appears that you are doing a "lime softening" process without intending it: given your very high CH, this is a GOOD thing. Do not stop! What's happening, apparently, is the high pH + the high TA are continuing to produce calcium particles that your filter is removing. This is GOOD!

So . . . don't add any more muriatic acid, now. Continue cleaning your pool. After you complete the DE test -- assuming the filter 'passes' the test, you can continue to add DE to help the filter remove very fine particles. It will result in more frequent backwashes, however.

NOTE: salt has NOTHING to do with TA, and has no effect on it. WaterMom already gave you the link to the alkalinity page -- you need to read it.

BUT, do NOT try to lower your TA yet; doing so will STOP the CH removal process!

Instead:
1. Complete the process of removing all the debris from your pool; vacuum up calcium dust as needed.
2. Complete the pool equipment form: http://pool9.net/pf-equip-form/ That will help us know how to help you.
3. Keep your chlorine high-ish
4. Test your FILL water, and report those results. You only need to test pH, TA and CH