How To: Shock Your Spa Without Additional Sanitiser

In Spa’s we usually use a non-chlorine oxidiser as a regular treatment to shock your spa, the most popular chemical is Potassium monopersulphate (MPS). It’s widely sold in Australia under names like “Spa Shock” or “Quick Fix” (by Poppits)” often labelled as a “non-chlorine oxidiser” or “non-chlorine shock”.

Here’s how it works:

Powerful Oxygen Release when added to water, MPS releases active oxygen molecules. These attack and break down organic matter at a molecular level.

Eliminates Chloramines/Bromamines in chlorine or bromine systems, MPS helps remove combined by-products (like chloramines or bromamines) that cause smells and irritation. This restores the sanitiser’s effectiveness and keeps the water fresh.

The spa needs to release the organic matter into the atmosphere so you need to leave the lid off the spa for 2 hours this will let the spa ‘breathe’.

Why do we need to Oxidise?

When we talk about oxidising in pools and spas, we’re referring to a chemical process that breaks down and removes unwanted organic contaminants from the water. These contaminants can include body oils, sweat, cosmetics, sunscreen, etc introduced during swimming or spa use.

Instead of “killing” like a sanitisers such as chlorine, bromine, hydrogen peroxide etc, oxidising is about destroying waste that builds up in the water. If left untreated, these contaminants can lead to cloudy water, unpleasant odours, and reduced sanitiser effectiveness.

Benefits for spa water care

Its great as it does not raise chlorine or bromine Levels unlike a chlorine-based shock. Instead, it supports the existing system by removing the “waste load,” leaving the sanitiser free to focus on killing germs and bacteria.

Fast Re-entry Time one of the biggest advantages of non-chlorine oxidisers is that you can usually use the spa again within 30 minutes of treatment (compared to chlorine shocks which often require hours for the chlorine level to drop to a safe level). Check your products instructions for specific information.

Eliminates odours by breaking down chloramines & bromamines

Activates bromide into bromine in bromine-based systems.

Gentle to eyes, skin, and spa surfaces compared with high-dose chlorine shock.

Using MPS with different sanitiser systems

Another significant benefit of a peroxy monopersulphate is that it is compatible with all four SPA sanitisers approved for use is Australia.

1. Bromine systems

MPS works as an oxidiser/activator, helping convert the bromide reserve in the water into active bromine but you will still need to monitor & control your bromine levels. In bromine spas, MPS is often dosed weekly or after each use to maintain consistent sanitiser performance.

2. Chlorine systems

MPS removes organics so chlorine can concentrate on killing bacteria and viruses, improving water clarity and swimmer comfort. It also helps lower combined chlorine levels, reducing “chlorine smell.” MPS won’t increase your chlorine residual, you’ll still need to maintain your usual chlorine dosing.

3. Hydrogen Peroxide systems (e.g. Poppits®)

In peroxide-based spas such as Poppits and Peroxsil395, hydrogen peroxide is the primary sanitiser and MPS can be used to give an extra oxidation boost on a routine basis.

• When to use:

as a “rescue” oxidiser if water clarity or odour issues appear, or if you need to quickly break down bather waste after high load.

Add it 4hrs before topping up your peroxide

• Caution: MPS can slightly raise sulphate levels, which may not be ideal for very long-term use in peroxide spas. Always check with the peroxide product’s manufacturer for compatibility, and avoid over-dosing.

4. Polyhexanide Hydrochloride (Spa Sanitiser)

Spa Sanitiser is a sanitiser but not an oxidiser, so an additional oxidising step is required to remove organics. In these spas, MPS should be used routinely to oxidise bather waste and prevent organic build-up that could cause cloudy water or biofilm.

• When to use: Add routinely every week when you add spa sanitiser & clarifier and also after every spa use.

General dosing guidance

(Always follow the exact rate on your product label.)

• Initial / heavy-use shock: ~30 g per 1,000 L
• Weekly maintenance: ~15 g per 1,000 L
• Broadcast evenly over the water with pumps running, or pre-dissolve in a clean plastic bucket of water.
• Run the spa for 10–30 minutes to circulate.
• Wait the label-specified time before using the spa.

Bottom line

Potassium monopersulphate is a versatile oxidiser for Australian spas. Its compatible with all 4 sanitisers approved for use in Australia so it’s an essential chemical to have on hand.

Always allow your spa to ‘breathe’ when shocking (remove the lid for a couple of hours) so the oxidising process can be completed.  Always follow the label instructions, always maintain your primary sanitiser, and use MPS as part of a balanced spa maintenance routine for the best results.