As a result of yesterday’s post regarding test kits for hydrogen peroxide in swimming pools we received a number of questions from readers asking if they should switch to peroxide instead of chlorine and also if hydrogen peroxide as the main sanitizer would save them money.
Comparison of required concentrations?
Swimming pools can, under certain circumstances (i.e. with a pass-through UV water filter), remain ‘safe’ for use with a free chlorine concentration of 0.5ppm while the same pool using hydrogen peroxide would require a concentration of around 30ppm to 40ppm… and sometimes more.
Mathematically, and on a good day, it would require 60 times the amount of hydrogen peroxide (or more!) to do the same job as free chlorine in this example.
When last we checked a gallon of 27% or 35% hydrogen peroxide shock had a cost of around $15 to $25 (see Splashes Oxidizer at In the Swim)… and in those concentrations it would require approximately 1 gallon of shock per 10,000 gallons of pool water to reach a 30ppm and 40ppm concentration.
Please note that the aforementioned ‘math’ also assumes a normal biological contaminant load — meaning no excessive amounts of body oils, algae, leaves, dead animals, feces, etc. in the water at the time the shock gets added.
By comparison, a gallon of liquid chlorine still costs around $5 or $7 at the local pool store… and may treat the same amount of water with a slightly higher than usual amount of biological contaminants.
Possible problem with use of hydrogen peroxide as main sanitizer?
Aside from cost — and in case you did not know, hydrogen peroxide volatilizes (i.e. leaves the water) at a faster rate than chlorine meaning you will need to add it more frequently — we have seen a number of cases where swimming pools with DE (diatomaceous earth — that ‘finely ground white powder’ added through the skimmer after backwashing) using hydrogen peroxide on a regular basis have had issues with the filter elements getting clogged prematurely and requiring acid washing more often than expected.
We have read in a few places that the hydrogen peroxide actually breaks down the diatomaceous earth leaving the cloth filter elements susceptible to clogging by contaminants passing through the filter. The diatomaceous earth, under normal circumstances, coats the cloth filter elements and keeps contaminants from getting trapped in their mesh. Backwashing the filter then shakes loose the DE as well as the contaminants and they get flushed out of the system.
Is peroxide safer to handle than chlorine?
Not really. Both have the power to cause eye, skin and nose irritation. Read the warnings on both products before handling either one and ALWAYS USE PRECAUTION!
When in doubt, don’t do it! Seek advice from a pool water professional before adding chemicals you do not know much about to your water… because bad things CAN and WILL happen if you do not take the proper precautions!
As an example, adding chlorine to a biguanide pool, or vice versa, will result in the formation of really nasty solids that take a lot of time, effort, energy, and money to remove. Granted not a health hazard, but still a really nasty problem to have to deal with!
Why do people switch from chlorine/bromine to peroxide?
Typically the reason for switching from chlorine/bromine to an alternate sanitizing system like peroxide involves a person having allergic reactions or sensitivity to chlorine/bromine. In cases like these no options exist and other water sanitizing systems must get used.
Other reasons for switching to a non-chlorine/bromine sanitizer system include pool professionals not telling ‘the truth’ about pool sanitizing options so they can make more money, people having bad experiences with chlorine/bromine in the past due to improperly maintained pools, and often times just not fully understanding the ins and outs of each pool sanitizing system.
No matter what, TEST for sanitizer levels regularly!
Regardless of whether you choose chlorine, bromine, peroxide, ozone, biguanide, or some other type of sanitizer, remember that it serves your first (and most important!) line of defense against potentially hazardous pool water contaminants and algae.
The only way to way to know for sure that your swimming pool contains the correct concentration of sanitizer… is to test the water!