Safe Free Chlorine Level

[benadkins]

I am just starting to do my own pool maintenance. I have had a major battle with algae this year and in past years. It looks to me like the best solution for my pool is to use Clorox to maintain the proper FC level. Up to this point I have been using chlorine tablets which have caused the CYA to increase to 80. Consequently, I have continued to have an algae problem.

My plan is to decrease the CYA to between 30 & 50 by draining water from the pool. Once I do this, I will shock the pool to get rid of any algae that is present. According to Pool Math the recommended FC level for my pool is 6-8 and the shock level is between 20 & 29. My plan is that I will shock the pool about once a week to prevent the return of algae. My concern is that I have read that it is not safe to enter a pool with the FC level greater than 9. Therefore, I will have to monitor the pool after shocking to allow the FC to drop below 10 before swimming in it - is this correct?

Basic pool facts: 33,000 gallons, Pebble Tec finish, Paramount in-floor water jet circulation system, Sta-Rite cartridge filters, Pent-Air variable speed pump.


I would appreciate any comments/recommendations regarding my plan. Your TFP site has been very helpful and extremely educational. Prior to my association with TFP, I was using test strips and occasionally taking a water sample to a pool store, which always ended up costing a fortune in chemicals. With your help, I look forward to having a Trouble Free Pool. Thanks!

 

[cfherrman]

A good rule of thumb is to ignore any traditional pool info as they ignore the last 40 years of science on pools. If you follow tfpc you do not need to shock the pool weekly, or ever. In tfpc you closely regulate the fc level to your cya level and nothing grows, ever. One will have to perform a slam if they forgot to take care of the pool or during opening. There is members that have gone over 4 years without a slam. I have never done a slam but this is year one for me on tfpc.

Your pool is safe to swim in if:

Can visually see the deep end, can be cloudy but if you can see the floor in the deep end.

Fc up to slam level for your cya, round up your cya to a whole 10's and that's your cya level, I'm guessing 29 is your shock level, so 28.99 fc and lower you are fine to swim in, the clorine at this level is less harsh then 3 fc and 0 cya. Science wins the day!

There is one more requirement, I can't remember, someone will back me up soon.

I am having a pool party today for my daughter's 6th birthday, about 20 kids are coming, I didn't do anything different for my pool and it's as clear as can be, I will boost the fc a bit for swimmer load.

 

[Topher55]

Shock level is 40% of cya. After you do a partial drain and fill check the cya and slam accordingly.

It is safe to swim at slam level and below, again this is determined by your cya level.

With the tfp method you have to get your head wrapped around the FC to CYA ratio. It's never __FC is shock or save level. It's all based on your CYA. shock level is 40% of cya, minimum is 7.5% of cya.

 

[Mike1162]

I think the FC levels you mentioned are a just a little low for CYA @ 80. Here's the chart:
https://www.troublefreepool.com/content/128-chlorine-cya-chart-slam-shock