According to ChemGeeks spreadsheet my water is balanced with these numbers

[ubalr1]

Many folks are reluctant to completely drain even a gunite pool, so draining 60% of the pool twice is sometimes easier and a nice, buffered way to keep chemistry in balance throughout the process.

A single drain of 95-100% saves me 4000 to 5000 gallons of water. A valuable resource here in the desert. I can see the benefits to both methods though.

[chem geek]

OK, now that your CH number is more "normal", at least for your fill water, it is true that you don't need to go as low in TA (the 50 I mentioned). 80 should be fine and yes, some people run with more but you then run the risk of fighting rising pH, especially if you have water features or other sources of aeration. So if your final CH in your pool is around 300 and your TA gets to 80-100 you are in very good shape indeed, but don't worry about this combination being perfect (i.e. CSI=0) since it does not have to be.

As for doing a full refill in a safe way that doesn't have your pool crack from underground water table pressure, some people have found that they can use a large plastic pool cover that extends way beyond the edges of the pool (a very large plastic sheet, actually, not a solar cover). Then with this on top of the pool, they simultaneously drain the water from under the cover while filling with water on top of the cover. This way, you can replace as much water as you want without ever having a lower water level and doing this efficiently to use the least amount of water possible. Really neat and I wish I could remember who said it or where the post was since I'd love to give credit where credit is due (I just love clever ideas). You could probably use a solar cover for this technique, though there will be some mixing at the edges (hopefully not too much).

By the way, how in the heck did you ever get your pool water's CH to 990? Did you add tons of calcium chloride pellets at some point?

Richard

[ubalr1]

By the way, how in the heck did you ever get your pool water's CH to 990? Did you add tons of calcium chloride pellets at some point?

Richard

I wish I knew for sure how it got so high. I suppose the test could be in error. I followed the Taylor instructions to the "T". To avoid false readings (due to fading endpoint) I added five drops of titrant (hardness reagent) to the sample first and then continued the test as usual. At 99 drops the sample finally turned blue. Next time I check it I'll follow the procedure for high CH (smaller sample, less drops, multiply by 25).