Chemical mistake when slamming - What are the side effects

[Richard_S]

Ok, my fault....

opened up the pool this year and time for the trusted method of SLAMing the pool. Having done this for several years now with perfect results, I know how much liquid Chlorine I need to put in the pool....So down to the local pool store to purchase my 2 x 20L containers of Chlorine.

having bought both, I poured in approx 12L of what I thought was Chlorine into the pool....Went away for a few hours.....Came back to test pool and found NO Chlorine, so popped another 10L in......and just as I was rinsing the container in the pool I realised that this was actually Hydrogen Peroxide - same colour container, same colour lid, same colour label, just different name...

A quick moment of panic ensued and I headed over to the pool store to discuss. Turns out that it's brilliant at shocking pools but you need to use much smaller amounts. My pool would have been fine with 3L not 20L. I was advised that it would not harm anything apart from the bacteria, but that it would essentially destroy any Chlorine in the pool too, hence the zero reading of Chlorine during testing. On the upside I paid for Chlorine and got something three times more expensive...

I am now running the filtration system 24hrs per day and also the pool pilot chlorinator and have a crystal clear pool, with a view that at some stage the chlorine will come back into action once the hydrogen peroxide has dissipated.

My questions to all you clever people are;
1) how long will this destroy chlorine at these levels so make any chlorine testing pointless?
2) Is there an effective way of speeding up the reaction of hydrogen peroxide without refilling the pool - to effectively get rid of it?
3) Should I be worried....?

Many thanks for any help

 

[domct203]

I'm no chemistry expert, but I know that the H2O2 is not a sanitizer/disinfectant, but an oxidizer that will eat chlorine as fast as you can put it in.

I've reached out for help from others that are much more experienced with chemistry than I am, I'm sure someone will be along soon to offer more info.

 

[Richard_S]

Thanks for that. Yes, realise that H2O2 destroys chlorine, just wondered how long this effect could go on for with the concentrations that I have put in and make any testing redundant. As the Chlorine production is "free" I am simply letting the chlorinator do it's thing until such time as it finally sticks around.

 

[JamesW]

Same thing happened at the Olympics. They were using ORP as process control. Since hydrogen peroxide creates an ORP reading, the error was missed.

Basically need to SLAM to get rid of the hydrogen peroxide. What concentration was the hydrogen peroxide?

 

[JoyfulNoise]

There's no point in speeding anything up by making more of a chemical soup. Just keep adding chlorine until you start getting a reading. The reaction between peroxide and chlorine is nearly instantaneous so, like having ammonia in the pool, you just keep adding chlorine until all the peroxide is gone. Roughly speaking, the rule of thumb is that the volume of 3% hydrogen peroxide neutralizes the same volume of 6% bleach. Also, the reaction is acidic so it will lower pH. You may need to readjust pH after the chlorine starts to hold.

A quick and dirty determination can be made by adding DPD powder to the water sample and then the R-0003 drops. The peroxide will oxidize the iodide to iodine and the iodine will react with the DPD to turn it pink. The number of drops of R-0871 titration will give you the total oxidizer level in units of chlorine gas.

But even without all that testing, just add chlorine until you see a reading.

 

[Richard_S]

Joyful, thanks for that - interested to here about the pH. When I last checked it it was fine, but let's see what a week of chlorination does. Will also see what the DPD test gives and report back.

James - I think that this is what the press suggested - or at least that was there excuse - and they sorted it by changing the water. They didn't actually bother to SLAM. My main concern is if the peroxide sticks around or if it naturally degrades. I think somewhere I read that UV light is important for the chemical process to happen....Perhaps someone could confirm?

 

[BestJoeyEver]

They didn't actually bother to SLAM.

In their defense, they couldn't really wait around for a SLAM, there was an Olympic competition going on!

 

[Richard_S]

In their defense, they couldn't really wait around for a SLAM, there was an Olympic competition going on!

No appreciate that!! Sadly I don't have a spare pool of water to swap things over as they did. I'm wondering whether it's actually worth adding liquid Chlorine or just letting the chlorinator do it's thing over time. It might take a little longer but at least I wouldn't be throwing good money after bad....and I'm not actually in any hurry as no one will be using the pool for the next month. More's the point, if I don't quickly add chlorine will the sanitising aspect be compromised sooner rather than later, leading to the pool going green and me having to start the whole process again.

 

[domct203]

No appreciate that!! Sadly I don't have a spare pool of water to swap things over as they did. I'm wondering whether it's actually worth adding liquid Chlorine or just letting the chlorinator do it's thing over time. It might take a little longer but at least I wouldn't be throwing good money after bad....and I'm not actually in any hurry as no one will be using the pool for the next month.

Pay me now, pay me later.....

If you let it ride, the pool will most likely go green, requiring large amounts of chlorine to clear (SLAM).

Why not use bleach to get FC to start to hold, then try just maintaining that with the SWG until you can really devote time for the SLAM.

 

[JoyfulNoise]

Dom is right. You need to neutralize the H2O2 or else your sanitizer levels will be ineffective. Peroxide is a terrible sanitizer compared to chlorine and your pool will be improperly sanitized while you wait for it all to degrade naturally.

 

[BestJoeyEver]

Maybe I'm wrong, but it sounds like OP is thinking the H²O² will just keep on neutralizing the CL until it dissipates naturally, but I *believe* that they neutralize each other. So as you add Chlorine, it is neutralized by the Holy Spirit, but the Hydrogen Peroxide is also in turn neutralized by the chlorine. So if you keep dumping chorine, they will eat each other until there's nothing left, then the FC will start to hold. If I'm correct on that then the sooner the better.


Edit: Obviously by 'Holy Spirit' I mean hydrogen Peroxide. Otherwise we're talking about a WHOLE DIFFERENT kind of cleansing.

 

[JoyfulNoise]

Maybe I'm wrong, but it sounds like OP is thinking the H²O² will just keep on neutralizing the CL until it dissipates naturally, but I *believe* that they neutralize each other. So as you add Chlorine, it is neutralized by the Holy Spirit, but the Hydrogen Peroxide is also in turn neutralized by the chlorine. So if you keep dumping chorine, they will eat each other until there's nothing left, then the FC will start to hold. If I'm correct on that then the sooner the better.


Edit: Obviously by 'Holy Spirit' I mean hydrogen Peroxide. Otherwise we're talking about a WHOLE DIFFERENT kind of cleansing.

Agreed. On all points.

Yes, a very epic autocorrect...

 

[Richard_S]

Ok, so from what I am getting here, best to add a large measure of liquid Chlorine to get rid of the "Holy spirit" as soon as rather than letting nature take its course.

 

[needsajet]

And keep it at high FC until you can fit a SLAM into your life

 

[domct203]

Ok, so from what I am getting here, best to add a large measure of liquid Chlorine to get rid of the "Holy spirit" as soon as rather than letting nature take its course.

Yes, but don't go 'nuking the pool', lets be sensible here.

What is the CYA level? I would aim for a FC of 50-60% of CYA until FC starts to hold, then drop back to 40% and SLAM.

So if the pool has a CYA of 40ppm, aim for FC of 22ppm (40 x 0.55) until the FC holds, then maintain a FC of 16ppm for the duration of the SLAM.

If the pool has zero CYA, dose FC to 10ppm.

To quickly oxidize the H2O2, you need to stay on top of the FC at first......

1) Add chlorine to get to 22ppm (for CYA 40ppm)
2) Wait 10 min then test
. 2a) If FC is less than 50% of target (11ppm), repeat steps from #1.
. 2b) If FC is greater then 50% of target go to step #3
3) SLAM

 

[BestJoeyEver]

FYI, it will likely seem. Like you're getting nowhere at first, then all of a sudden you'll male progress. Don't get discouraged!

 

[Richard_S]

I'm having to do this all at a distance as I'm not actually at the pool or in fact in the country where the pool is.... Sadly I didn't catch the process outlined in the posts above and Chlorine has gone in at high levels...can't do the "little by little" approach. Hopefully the quantity of Chlorine will be sufficient to combine with the peroxide and get things back on track. Effectively I am doing a one time only shock to get rid of the peroxide.. Frankly what with the peroxide and the Chlorine there ain't going to be anything living in there.... Just need to get it down to the sensible swimming levels....And I have a month to achieve this.

 

[domct203]

I'm having to do this all at a distance as I'm not actually at the pool or in fact in the country where the pool is.... Sadly I didn't catch the process outlined in the posts above and Chlorine has gone in at high levels...can't do the "little by little" approach. Hopefully the quantity of Chlorine will be sufficient to combine with the peroxide and get things back on track. Effectively I am doing a one time only shock to get rid of the peroxide.. Frankly what with the peroxide and the Chlorine there ain't going to be anything living in there.... Just need to get it down to the sensible swimming levels....And I have a month to achieve this.

I understand your limitations, you'll have to do the best you can then.

BTW- H2O2 is NOT a sanitizer, and the sanitizer (chlorine) you are adding is being immediately oxidized by the H2O2, this means your pool is without a sanitizer if FC=0. A pool without proper levels of sanitizer will go green, guaranteed.

 

[Richard_S]

Thankfully the weather is not too warm yet, although pool is at 21-22c at mo... fingers crossed that I will win the chlorine battle before the algae does.

 

[JoyfulNoise]

I will make the following correction for technical clarification purposes. Peroxide is considered a sanitizer it is just a very poor sanitizer for swimming pool applications. In order to act as a sanitizer with equivalent CT kill times as chlorine, the peroxide levels would have to be so high (somewhere above 100ppm) that water would be very uncomfortable to swim in (stinging eye, bleached swimsuits, etc). So, as long as you keep adding chlorine and maintaining a measurable level of chlorine (try using an OTO test kit to see the total chlorine levels), you should be ok. Even if algae got started in the pool (cloudiness), a very quick SLAM would easily take care of it. You're only in danger of a green swamp if someone lets the pool just sit around with no chlorine in it.