Oxidizer (Hydrogen Peroxide)
The second half of a biguanide system. Sanitizing and oxidising are two jobs, and biguanide only does one of them.
- Ideal range
- 25 – 40 mg/L
- Measured in
- mg/L
A manufacturer operating target, not a health limit — the platform will flag a reading outside it as worth attention, never as unsafe.
What it is
Chlorine both kills organisms and burns off the organic debris they leave behind — sweat, sunscreen, skin oils, pollen. Biguanide does the first and not the second, so a biguanide pool adds hydrogen peroxide separately to handle the oxidising. It is the direct equivalent of shocking a chlorine pool, except that it is a routine maintained level rather than an occasional event.
Why it matters
Without enough oxidizer the organic load simply accumulates. The pool can hold a perfect sanitizer reading and still go dull, cloudy or slick underfoot, because nothing is breaking down what the swimmers left behind. It is the reading people forget, and cloudy biguanide water is nearly always this rather than the sanitizer.
How to measure it
Read it off the same biguanide strip that reads your sanitizer — the two pads sit side by side, which is the point of the strip.
Test strips
- How trustworthy
- Dependable
- Cost
- Low cost
- Effort
- Under a minute, wherever you drew the sample
A plastic strip with reagent pads on it. Dip it, hold it level, and match each pad against the chart on the bottle at the time the label tells you to. Most strips read several parameters at once.
The peroxide pad on a biguanide strip. Read it at the time the bottle specifies; peroxide pads in particular keep developing and a late reading runs high.
Where to find it: Pool shops, hardware stores, supermarkets and online, sold both per parameter and as multi-packs. Buy strips made for your kind of water: pool strips and drinking water strips read very different scales for the same chemistry.
Liquid reagent kit, colour match
- How trustworthy
- Dependable
- Cost
- Low cost
- Effort
- A couple of minutes, at a sink or poolside
A measured sample in a plastic comparator block, a few drops of reagent, and a colour you match against printed standards beside the tube. The two-tube kit sold everywhere for pools is this.
A titration for peroxide exists and is more precise, but for a level you are topping up on a weekly schedule the strip is generally enough.
Where to find it: Pool shops and online. Reagents expire, so buy replacement bottles rather than a whole new kit each season.
Taking the sample
For several of these the sample is where the error is, and no instrument recovers from a bad one.
- • Test before the weekly dose rather than after, so you are measuring what is left rather than what you just added.
If it is too low
Organic waste is building up faster than it is being destroyed. Expect water that looks flat or hazy before anything else goes wrong.
- • Add the oxidizer supplied for your system, on the schedule the brand specifies — typically weekly rather than as-needed.
- • Increase the frequency after heavy bather load or a spell of hot weather, which is when the organic load rises.
If it is too high
Wasteful rather than dangerous, though very high levels can interfere with the sanitizer reading on some test strips.
- • Skip the next scheduled dose and let it fall on its own.
- • Check you are not dosing on a fixed schedule while also shocking after every party; those add up.
Common questions
Can I use ordinary household hydrogen peroxide?
It is the wrong strength and the wrong formulation. Pool oxidizer is a far more concentrated, stabilised peroxide sold for the purpose; household peroxide is dilute enough that you would need an impractical quantity, and it is not stabilised for pool water.
Is this the same as shocking the pool?
It is the same job done continuously rather than in bursts. Chlorine pools shock to burn off accumulated organics; a biguanide pool keeps an oxidizer level present all the time so the burning-off is always happening.
WiseWaterGauge helps you record and understand your own readings. It is not a substitute for a certified laboratory test, and nothing here is medical or regulatory advice. If a health parameter is out of range, confirm it with an accredited lab and speak to your water provider.