Ever looked outside, seen your pool, and thought… “Why does it look like a glass of diluted milk?”
You’re not alone – cloudy pool water is one of the most common questions we get.
And yes, chemicals matter…
But cloudy water is almost always a sign that something else in the system isn’t happy.
Here’s what’s really going on – and how to clear it quickly.
1. Your Filtration Isn’t Keeping Up
This is the number one culprit. Cloudiness happens when the filter can no longer grab the tiny particles floating in your water.
Check these:
✔ Filter pressure – If the pressure is 10 PSI/50 kPa higher than normal, it’s overdue for a clean or backwash.
✔ Pump run time – NZ pools typically need 8–10 hours a day in summer. Less than that = water sitting still = cloudy.
✔ Dirty or old media – Sand older than 5 years? Cartridge clogged or collapsing? Biofilm building up on the media?
All of these reduce filtration and create cloudy water.
2. Low Chlorine – Even if It Looks Fine
Cloudiness often appears when chlorine can’t keep up with:
- heat
- heavy swimming
- rain
- debris
- sunscreen and body oils from swimmers
- organic material blowing into the pool
If your free chlorine is low or CYA (stabiliser) is way off, sanitising simply… stops. Even if the pool still looks blue-ish, bacteria and micro-organisms scatter light and make the pool look hazy.
3. Early-Stage Algae (The Cloudiness Before the Green)
Cloudiness is often your first warning sign that algae is starting to grow – long before you see green. Warm water + low chlorine + sunlight = the perfect breeding ground.
If the pool suddenly goes from sparkling → dull → cloudy? That’s almost always algae waking up.
A proper shock, good brushing, and correct chlorine levels stop it in its tracks.
4. Unbalanced Water Chemistry
If your water balance isn’t right, it can literally make the pool look cloudy even when it’s clean. The biggest offenders are:
• High pH – Chlorine becomes “lazy” and doesn’t sanitise properly.
• High Total Alkalinity – Causes pH to rise, increases risk of scaling and causes cloudiness.
• High Calcium Hardness – Common in some areas of Canterbury – high CH can turn water milky, cause flakes, and clog equipment. If these levels drift, clarity ALWAYS suffers.
Weekly testing is essential – or bring a sample in-store and we’ll test it for free.
5. Contaminants & Tiny Debris That Your Filter Can’t Catch
These can include:
- pollen (big issue during Christchurch nor’westers)
- dust
- fine silt
- sunscreen
- hair and skin oils
- body lotions
- tiny insects
- Shocking the pool + using clarifiers or a product like Pool Complete helps clump these micro-particles so your filter can remove them.
The Fastest Way to Fix Cloudy Water
- Test pH, chlorine, and alkalinity immediately
- Give the pool a long run time (8–12 hrs)
- Backwash or clean your filter
- Shock the pool (chlorine shock or non-chlorine shock depending on chlorine levels)
- Brush the entire pool
- Use a clarifier or Pool Complete if needed
- Re-test in 24 hours
Most cloudy pools clear within 1–2 days if these steps are followed.
Cloudy Water = A Warning Sign (Not a Mystery) When your pool goes cloudy, it’s telling you that:
- filtration isn’t keeping up
- sanitiser is too low
- something is growing
- or particles are floating around that your filter can’t catch
Sort it early and it’s an easy fix.
Ignore it… and it turns into algae.
If you want tailored advice, just bring a sample into the store. We’ll test it and give you a simple, step-by-step plan to get your water clear again.
