Need some math done please

[shub_31]

Im trying to lower my cya that is currently 100ppm. I dropped my pool about 11''. Its 18X36 grecian stated at 16,500gl. Any guess how much water i dumped and how low can I expect my cya to drop. I want to eventually get to adding only the 3qt jugs of bleach. instead of 2gallons. Thanks

[AnnaK]

That water volume seems very low for this size pool. How deep is your deep and and how deep is the shallow end? For 16500 gal. an 18x36 pool can only be 3.4 ft deep.

If you dropped the level by a ~ foot (11") then that is 18*36*7.5 = 4860 gal or 29% of the 16500 total in a flat bottom pool. So your ppm of cya is also dropped by 29%.

But I question the veracity because it's based on assumptions without enough information.

You can just let the CYA drift down on its own via the occasional refill. Do you have a sand filter? Backwashing and rinsing uses up water that has to be replaced. Use more chlorine for now, let time pass, test, and adjust your chlorine additions accordingly. All a high CYA really means is that you need more chlorine, as you've found out.

In the meantime, you might walk around with a measuring tape, record the dimensions of your pool (L x W x D) and make a note of its optimum volume. That's really useful information to have.

[shub_31]

omg! i just thought of something from your reply. my blueprint says 16500 imperial gl and i thought it was the same as us. my pool is actually 19000. no wonder my bleach isnt reading what i thought it should be. i thought i just had some extra water. i need to figure some things at now. thanks for the reply

[CarlD]

If your pool is clear, then you can simply maintain a residual Free Chlorine value of 8 to 15ppm for the season, the range for CYA of 100ppm or more.
You'll find you use less chlorine, too---but you MUST keep it in that range. If your CYA is really far beyond 100ppm, stay closer to the 15ppm level. You'll STILL use less chlorine.

Carl

[shub_31]

well i checked my cya after my water drain a pretty much no change. Still 100 I remember my builder saying that he put the skimmer in higher so that I can have a higher water level. Maybe I have more than 20000gl. Anyways, I guess Ill maintain the high fc level and see what happens next year. The pool is clear but with the rain and sun my levels drop more than i thought. Can someone tell me if my cc is less than 1 (all the time) and my fc drops 4-6ppm (daily) does that mean i have a problem or is that normal. Being said with a high CYA Thanks

[aylad]

You can tell if it's normal or not by testing at night after the sun is off the pool and again in the morning before the sun hits the pool. If you lose more than 1 ppm chlorine during that time, it's not normal.

Janet

[shub_31]

Im confused. Everyone says to add chemicals at night so they can work. If thats the case shouldnt you drop ppms every night based on swimming in it.

[kelemvor]

The reason to add chems at night is to avoid the sunlight. Sunlight will consume chlorine, the ammount burned up by the sun can be reduced by adding cyanuric acid. At night, you don't have the sunlight concern so all that chlorine you add can work to sanitize until the sun hits it in the morning.

Swimming introduces sweat, bacteria etc so that does consume some chlorine as the chlorine sanitizes away these things. I don't know how you could measure how much, though.