CYA Levels and SW pool with cover

[akropp]

I'm a new pool owner/maintainer. My pool was plastered/filled last winter, but they closed it without adding the salt, so I just opened it a couple of weeks ago. They had originally just cleaned it, shocked it, and balanced it, and threw in some chlorine tabs to make it swimmable for the Memorial Day weekend, and then came back a couple of days ago to add the salt and set up the SWG. I had been watching the levels and adjusting them prior to the pool guy coming back, but the one standout was that they never added any CYA (my initial readings were 0). After two weeks on trichlor tabs, the level was somewhere between 20 and 30 (I'm not that practiced at that test yet), but definitely nowhere close to the TFP suggested 60-80.

When they finally came to set up the SWG, I asked about the CYA level, and he said given that I have a pool cover and will be keeping it covered whenever I am not using it (little kids == scared wife == pool definitely closed all the time), I shouldn't need to worry about the CYA level or the sun burning off the FC.

Any thoughts on this? I don't really have a sense of just how fast sunlight will reduce the FC -- when I test in the morning, the FC is in the 3-5 range from the SWG. I just want to make sure if we have a long day of the kids playing in the pool my levels aren't going to drop too low.

Since I know you'll ask
FC 5
CC 0
PH 7.8 *** I added 2 quarts of MA
TA ~100-110 ** This has remained stubbornly high since they filled the pool
CH 275 ** planning to add some more to get up to the TFP recommended 350-450 for SW pools
CYA 30
Salt 3300
Temp 88 degrees!

 

[mknauss]

Not sure I would say you do not have to worry about CYA or sun burning off your FC, unless you plan to only swim at night!

You could get away with a lower CYA. Say 40-50 ppm. And you would need to ramp your SWCG up to create more FC on swim days. It will be up to you how you manage that.

It will probably be easier to run your normal FC higher than target range, say 10-12% of CYA, so on swim days you do not go below minimum. You may find you do not need to adjust the SWCG much for those swim days if you do that.

 

[santacruzpool]

I have a pool cover and the pool is covered most of the time.

I have decided to keep my CYA at around 40 - and I shoot for FC of 4-5 (the same as the 10-12% that Marty mentions above).

However, my automation allows me to adjust my SWCG % based on being open or covered - so I don't need to move it around too much. For example, currently I run the SWCG at 25% when covered, and 40% when open. I then adjust the pump run time up or down seasonally as the FC needs change. I will on occasion tweak the SWCG % a little bit as well to keep me closer to my target numbers.

 

[akropp]

Yeh, I wish my automation would let me set something like that up. It looks like on days when I leave the cover closed all day, FC gets up to around 6.5, but open it up for the afternoon and it drops to around 2. I guess I’ll bring up the CYA a bit so I can just run the SWG at a lower output and not have to worry about losing too much FC when I open it.