Effect of rain

chasut

Silver Supporter
Mar 17, 2020
6
Austin/TX
It is that time of year. We have had two significant rain events in the last month or so and another on its way. As expected, the rain diluted my salt content by about 300ppm on a basis of ~3500. Not unusual as the pool auto-drains with heavy rain.

Question: Is it reasonable to assume that CYA has been reduced by a similar amount?

The reason I ask is that I am seeing increased chlorine usage. The CYA test is just not that Precise. Based on stabilizer additions I should be at 83ppm with the dot disappearing at the 80 mark. Last test though I testing at 70ppm. Given the amount of sun the pool gets, I am looking to stay in the 80’s, but certainly don’t want to overshoot the mark (like I recently did with salt)

TIA
 

Richard320

TFP Expert
LifeTime Supporter
Jan 6, 2010
23,633
San Dimas, CA (LA County)
Yes.

Rainwater has no CH, no salt, no CYA, no TA. If you replace 10% of the water with rain, they will go down 10%

pH could go either way, depending on the pH of the rain and how aerated the surface of the pool gets and how much TA was already in there.
 

chasut

Silver Supporter
Mar 17, 2020
6
Austin/TX
Yes.

Rainwater has no CH, no salt, no CYA, no TA. If you replace 10% of the water with rain, they will go down 10%

pH could go either way, depending on the pH of the rain and how aerated the surface of the pool gets and how much TA was already in there.
Excellent, thank you