Shock and high CYA

[Jmerich]

Hi,
I have a couple of questions.

I am going to shock my pool for the first time (the real way with liquid and not powdered "shock").

My CYA is 100 so. Know I need LOTS of chlorine per the calculator.

My questions:
1. Is it better to do a partial drain first (few inches so I can water my lawn. In so cal drought)
2. If I water my lawn, what is an OK chlorine level to not harm vegetation?
3. How soon can we swim after the shock?

Thanks!

 

[RobbieH]

Are you sure the CYA is 100? How is this being measured? When CYA reads 100, it very often can be much higher as most tests top out at 100.

I have never seen FC hurt a lawn, even at shock level. And if you will lower the CYA level now, watering your lawn in the process, the shock process is going to be far cheaper and easier.

You can swim when the shock process is complete, and FC has fallen below shock level.

You've read How to Perform the Shock Process in Pool School?

 

[Jmerich]

More info. I have a small amount of algae I noticed on the tile grout. I have also noticed an intermittent odor (can't really describe) when in the jacuzzi with the jets on. Could this algae be causing the odor? Water itself smells fine.

I have read over the shock process briefly but will re-read before I do anything.

 

[RobbieH]

Be sure you brush off that algae during the shock process.

An odd odor should always make you wonder what is going on. It doesn't smell of bleach?

 

[Jmerich]

No, I don't smell bleach, indicating chloramines. It smells kinda organic to me (earthy) but I'm not sure. Odor remained even after cleaning filter and new DE. It is quite a puzzle.

 

[RobbieH]

It's never a bad time to perform an OCLT. All it really requires is that you test after dark and again before the sun is on the pool.

pool-school/overnight_fc_test

You should see less than 1ppm loss overnight. And you are correct, this is the right thing to do at this point.

 

[linen]

We would recommend lowering your cya level (maybe down to 70 since you have a swg) before doing the shocking process.

 

[Jmerich]

I would like to exchange the water gradually in order to use the water on my lawn, but this will probably take too long to lower the CYA in a timely fashion. Will have to give this some more thought. Thanks for all the help. It is much appreciated.

 

[linen]

Well you can do the shocking process at higher cya levels, but it will likely take more bleach/liquid chlorine...and more vigilance during and after the shocking process.

 

[JohnN]

Have you done the diluted CYA test? Lie was said, most CYA tests read anything over 100 as 100, so it could be higher.

 

[Jmerich]

I did do the diluted test for CYA. I'm confident my level is 100