Chlorine levels after Hydrogen Peroxide treatment?

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arff

arff

Active member
Jun 23, 2022
31
Switzerland
Pool Size
120000
Surface
Vinyl
Chlorine
Salt Water Generator
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!
 
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.
 
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!
 
JamesW said:
How much and what strength (%)?
Click to expand...
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:
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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so here is the main question: should I be aggressively adding chlorine to get the chlorine up, waiting for the peroxide to decay then add chlorine, or gently add chlorine such that eventually over time it goes up?
 
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!).
 
arff said:
- Proper testing - looking to buy the TF Pro kit but need to figure shipping to Switzerland
Click to expand...
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.
 
JamesW said:
How much total chlorine did it take?
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Approx ... 15 liters of 4.8% bleach from my local supermarket.
I started to see sustained levels of FC after 10L, but I do not yet have an accurate testing kit and am using the combination of the cheap test kit and my redox probe on my SWCG to measure. Since the redox measure was still showing low and dropping slowly I continued from 10-15l. I'm away for a few days with the cover closed, and my SWCG is running about 7 hours a day with a combination control of constant output and redox measurement - so if all goes to plan, the level should build up to the setpoint by the time I get back on Sunday.
 
tim5055 said:
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.
Click to expand...
Thanks .... There is someone on ebay willing to ship me the 2005 SALT taylor kit so I might go that way...
 
The K-2005 doesn't have the FAS-DPD test, as a heads-up. You'd be looking for a K-2006c ideally (K-2006 without the 'c' has a smaller amount of the FAS/DPD reagents).
 
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