Gazebo over spa (no sun) = no need for CYA?

[KerryR]

Hi all,

This is my second post, I'm new to TFP. I have a TF100 that I use for my pool, but I haven't yet tested my spa water because I was using dichlor and the CYA is very high. I'll do a drain and refill soon. (While I've used the TF100 CYA test for my pool, I'm basing my high CYA level in the spa on results obtained with Aquacheck test strips, which show the CYA off the high end. I don't want to 'waste' a TF100 CYA test on water I plan on replacing soon...)

Here's my question: When I drain and refill, will I need to add CYA, by whatever method, even though my spa is under a gazebo and never sees the sun, except, perhaps for an hour or so very late in the day, if the cover is off (rare)? If CYA is primarily for UV stabilization, I'd think I could skip it if the spa doesn't see direct sun.

Any thoughts?

 

[Richard320]

Hi all,

This is my second post, I'm new to TFP. I have a TF100 that I use for my pool, but I haven't yet tested my spa water because I was using dichlor and the CYA is very high. I'll do a drain and refill soon. (While I've used the TF100 CYA test for my pool, I'm basing my high CYA level in the spa on results obtained with Aquacheck test strips, which show the CYA off the high end. I don't want to 'waste' a TF100 CYA test on water I plan on replacing soon...)

Here's my question: When I drain and refill, will I need to add CYA, by whatever method, even though my spa is under a gazebo and never sees the sun, except, perhaps for an hour or so very late in the day, if the cover is off (rare)? If CYA is primarily for UV stabilization, I'd think I could skip it if the spa doesn't see direct sun.

Any thoughts?

CYA also acts as a buffer. Think of buffered aspirin. It sort of takes the harsh edge off without lessening the effects.

3 FC at 30 CYA is actually easier on hair and skin and swimsuits than 1 FC at zero CYA. At 1 FC and zero CYA, you'll have .5 Cl₂.
3 FC at 30 CYA will be .06 Cl₂

The graph and a lot more technical info is in this thread: Pool Water Chemistry

 

[KerryR]

Thanks for the info!

I'll get some CYA into the water after I refill.

Interesting graph-- it also appears to illustrate why we need higher chlorine concentrations in the solution as CYA goes up, and that bacteria and algae don't die off at the same saturation. Cool stuff.

Thanks!