Chlorine levels after Hydrogen Peroxide treatment?

arff

Member
Jun 23, 2022
8
Switzerland
Hi,
my salt electrolysis died and my pool was very green due to unusually hot weather.
I ran my filter for 24hrs for 2 weeks with SLAM but there was still a green tinge and the water was murky, so I treated with H2O2 instead and in the meantime also installed a brand new salt electrolysis machine. I have rebalanced everything over the last few days; TAC, pH, chlorine stabilizer all within recommended levels and my water is crystal clean. But despite running the electrolysis for 24 hours for 4 days and even adding some slow release chlorine in my skimmers, I am unable to increase and see any chlorine in my pool when I test. My new electrolysis machine has a redox probe and also confirms excessively low chlorine despite running at 100% non-stop.

I know that H2O2 kills the Chlorine, but what are the recommendations for getting my chlorine back up and how long might it take?
How long is the H2O2 active, and how quickly should the chlorine level build back?

Thanks for any advice!
 

tim5055

Mod Squad
TFP Expert
LifeTime Supporter
May 11, 2014
11,393
Franklin, NC
It is going to take a while. You are going to use a lot of chlorine getting rid of the peroxide.....

Stick with liquid chlorine, solid forms of chlorine are adding things to the pool you don't want. Turn off the salt system. It doesn't produce enough chlorine to help and you are shortening it's life.

@JoyfulNoise - time for your expertise.
 

arff

Member
Jun 23, 2022
8
Switzerland
tim5055 - thanks for the advice. I shall act accordingly.

A few clarifications please:
1 - When you say "a while" - can that be quantified in anyway? Doesn't the peroxide react away and decay after a week? does the addition of chlorine help anything even though I am not seeing an effect, or should I simply wait a few more days for the peroxide to decay before adding chlorine?

2 - Also when you say that I am reducing the life of my salt system, are you implying normal wear/use of it running or does the generation of chlorine in the presence of peroxide particularly damage the salt cell?

Also another question I forgot to ask previously - I know that in theory, a zinc anode is recommended so I have put two zinc plates in my skimmers; does it actually make a difference in practice?

Many thanks!
 

arff

Member
Jun 23, 2022
8
Switzerland
How much and what strength (%)?
I have approx 120m3 pool. Based on the recommendation of my local pool expert, I added 20L of a product called Steriperox which does not give % strength but is labeled as 1.136Kg/L - this looks like specific gravity, but I am not sure what concentration this implies. The label on the product recommends 2L per 10m3 for a shock treatment so I was slightly under that recommendation.

PS - hunting on the net I found this chart: https://www.h2o2.com/images/Density-of-H2o2--(12-14).gif
If I am reading it correctly, 1.136Kg/L looks like 25-30% by weight? Is that possible?
 
Last edited:

tim5055

Mod Squad
TFP Expert
LifeTime Supporter
May 11, 2014
11,393
Franklin, NC
You are not waiting for the peroxide to decay, you are looking to have the chlorine eliminate it. In the US there are three acceptable pool sanitizers, chlorine, bromine and Biguanide (peroxide based sanitizer, usually under the trade name Baquicil). Biguanide takes a long time to oxidize out of the water.

Matt or James are the people ot answer the technical questions.
 

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JamesW

TFP Expert
Mar 2, 2011
29,540
Last edited:

arff

Member
Jun 23, 2022
8
Switzerland
Just to followup:
- followed the advice and found some cheap liquid chlorine at my local supermarket with no additives.
- I am now able to detect proper levels of free chlorine in my pool again!

Two next challenges:
- Proper testing - looking to buy the TF Pro kit but need to figure shipping to Switzerland
- My SWCG has a redox control, constant rate, and a combination of the two settings, so I need to figure out the best setting for my SWCG (Bayrol AS7)... I will try the combination as the pure redox setting seems not entirely reliable from other threads I have read.

In any case, thank you all for your help; I am very glad to have found this resource of knowledgeable people, to avoid having to filter what the pool store guys tell me (or better avoid them entirely!).
 

tim5055

Mod Squad
TFP Expert
LifeTime Supporter
May 11, 2014
11,393
Franklin, NC
- Proper testing - looking to buy the TF Pro kit but need to figure shipping to Switzerland
TF Test Kits is a reseller of Taylor chemicals and reagents. They are prohibited from selling overseas as Taylor has contract with other companies in other countries.

The next best thing to look for on the Continent is a test kit by LaMotte if it has the the all-important FAS/DPD chlorine test, not all of them do As a last resort, look for a LaMotte ColorQ. While this kit has many issues compared to drop based test kits it beats test strips in many ways.