1Free and combined chlorine
Test free chlorine with DPD 1 and total chlorine with DPD 1 + 3. Combined chlorine is total minus free, and it should always be lower than free.
WA limit: the WA Code recommends combined chlorine no more than 30% of free. Some other Australian guidelines set a maximum of 1.0 mg/L (ppm), ideally under 0.2 mg/L.
Combined chlorine high? Other Australian guidelines shock dose to at least 10 times the combined chlorine reading; follow the label for product and dose. Nobody swims during a shock dose. The WA Code’s in-use maximum for total chlorine is 8 mg/L.
Low sanitiser lets bacteria and algae grow, and that clouds the water. For the first day or two, algae can look like plain haze before it turns green.
Healthy WA warns that some domestic salt chlorinators can’t keep up in heavy use. The pool turns milky and shouldn’t be swum in until it’s clear.
The water is dirty. Restore sanitiser, following the label, then keep going through checks 2 and 3.
Sanitiser isn’t the cause. Move on to check 2.
2pH, alkalinity and calcium
Sanitiser fine but the water milky? Check the balance: test pH, alkalinity and total hardness with a LaMotte Insta-Test strip or bring a sample in for a Spin Touch analysis, and calcium hardness with a calcium hardness reagent or tablet test. Hardness salts coming out of solution cloud clean water. High pH, especially with high alkalinity or hardness, drops calcium carbonate out of solution, and high alkalinity and calcium hardness push the water towards cloudiness and scale. Correct pH, alkalinity and hardness.
Run the numbers through the LSI calculator, and see calcium scale and the LSI.
3Circulation and filtration
Air in the suction. Air in the water makes clean water cloudy. Bubbles coming back through the returns point to a suction-side leak. Check, in order:
- The water level. Low water lets the skimmer draw air. Some manufacturers recommend keeping it at least halfway up the skimmer box. Pump makers warn never to run the pump dry, as that can damage the mechanical seal.
- The pump lid and its O-ring, then the fittings and valves on the suction side.
Run time. Domestic systems are generally sized to turn the pool over in about 6–8 hours; a pump run well short of that won’t keep up. Manufacturers extend run times in hot weather and heavy bather load. Sunscreen, body oils and other swimmer residues cloud water on their own. An undersized pump or filter may never catch up.
The filter itself. Rising pressure means it’s dirty. Some manufacturers say backwash or clean at 40–50 kPa above the clean-filter reading; check the manual for your model. Worn media stops catching fine particles. Some manufacturers say replace the media if the backwash is still dirty after 2–3 minutes, the water won’t clear after treatment and a few backwashes, or a backwash no longer brings the pressure down. Sand can also clump or channel, letting water through unfiltered. Suspect the filter? Run the broken-lateral checks.
What “clear” looks like
You should clearly see the floor at the deep end from the pool edge. The WA Code’s test is a 150 mm Secchi disk on the bottom of the deepest part, visible from the concourse at 9 m. Can’t see the bottom? Nobody swims. Cloudiness also shields micro-organisms from the disinfectant.
The WA Code covers public and commercial aquatic facilities (including residential developments of 30 or more dwellings, B&Bs, farm-stays and retirement villages), not backyard pools, but it’s a useful benchmark.
When it isn’t chemistry or the plant
If the chemistry and plant are sound, the particles may simply be finer than a sand or cartridge filter can catch.
| What you see | Use |
|---|---|
| Hazy, or the bottom is still visible | A clarifier, such as AquaGUARD Crystal Clear Tab or AquaGUARD Crystal Clarity. It clumps the fine particles so the filter can catch them. |
| Very cloudy, or you can’t see the bottom | A floc, such as AquaGUARD Crystal Express. It clumps the particles so they drop to the floor with the pump off, usually overnight. Then vacuum them to waste. |
Never send floc through the filter. With a cartridge or DE filter, take the cartridge out or bypass the filter. With a sand filter, vacuum on Waste, never Filter. Follow the label for every dose.
Final step
Vacuuming to waste takes water out of the pool. Top up, then re-test and rebalance. For where vacuum-to-waste water can go in WA, see green pool recovery. If it clouds over again, go back to check 1.
Based on
- WA Health, Code of Practice for aquatic facilities
- Healthy WA, swimming pools and spas
- Australian state health guidelines for public aquatic facilities
- Pool equipment manufacturers’ installation and operating manuals
- Product labels and pool-chemical manufacturers’ trade guidance
Checked against these and other manufacturer and trade sources, October 2026. Always follow the manufacturer’s manual and the product label.
General information for pool and spa trade professionals. Every pool is different. This guide does not replace the product label, the SDS, the equipment manual or advice from a licensed tradesperson, and figures quoted from the WA Code of Practice apply to public aquatic facilities. To the extent permitted by law, AGent Sales & Services Pty Ltd accepts no liability for loss or damage arising from reliance on it. Website terms.