This is presented for informational purposes only. I'm not advocating this.

I have a 20,000 gallon inground pool with vinyl liner and sand filter. It's located in southern Ohio and I don't have any trees overhead or other things that might cause problems.

Last year (2006) was the first year I had a real pool. Fortunantely I found this site before opening the pool. Last year I ran CYA levels between 30 and 50, and tried to maintain proper pH. I was satisfied, but thought I would try something even easier this year.

This past season (2007), I opened the pool late April and closed it late September.

This entire past season, I didn't add anything except water and bleach. Except on opening, I never shocked it the entire season. When I opened the pool, it was really nasty - black water and baskets full of dead earthworms. I kept it at shock levels for about 3 days and vacuumed to waste about 3 times for very short periods of time to minimize water loss and get the really yucky stuff.

Within a week or so, it was sparkling.

My CYA level was not measurable, but there probably was some residual from last year.

All season, I simply brought the chlorine level up to about 3 ppm each evening after the sun went down. By the next evening, the level would be back to zero or near 0 ppm, and I would bring it back up again.

I seldom had HEAVY swim loads, but did a few times. In those cases, I would simply bring the level up to 3 ppm or slightly more BEFORE the party, and immediately bring it back up AFTER the party.

My kids and the neighborhood kids go back and forth between my pool and another pool in the neighborhood, and I'm told the other pool often burns their eyes, but mine doesn't.

These were the numbers after opening the pool and getting it clean:
FC=1.5 CC=0.5 TC=2.0 pH=7.6 Alk=90 Cal=150 Cya=0

These were the numbers when I closed the pool:
FC=0 CC=0 TC=0 pH=8.2 Alk=160 Cal=170 Cya=0

I didn't have any algae problems or anything. Take it for what it's worth. I don't expect this would work for a lot of pools, but I was pleased.