Pool flocculant clears cloudy water fastest, usually overnight, but it’s the harder job: you switch the pump off, let everything sink and then vacuum it out to waste. Clarifier is slower and gentler. It clumps the fine particles so your filter can catch them while the pump keeps running.
So the real question is how cloudy the water is, what filter you have and how much water you can afford to lose. Before you buy either bottle, though, find out why the water went cloudy in the first place. Otherwise it’ll just cloud up again next week. If you’d rather hand the whole thing over, our once-off pool cleaning service deals with cloudy water as part of the clean.
What causes cloudy pool water
Cloudy pool water is full of particles too small for the filter to hold. Neither product removes the cause, so check these first:
- Chemistry. High pH, high calcium or low chlorine all cloud water. Test before anything else.
- Dead algae. After a shock dose the dead cells hang in the water and turn it milky. That’s normal for a day or two.
- Filter problems. Worn sand, a dirty bed or a filter run too few hours a day lets fines straight through.
- Dust and debris. The summer south-easter blows fine dust and sand into Cape Town pools, and winter runoff can carry soil in from the garden.
- Overdosed products. Too much algaecide or clarifier can cloud the water by itself.
If the cloud appeared straight after a shock, read our guide to a cloudy pool after shocking before reaching for either product. Often patience and a good backwash are all it needs.
Pool flocculant vs clarifier: the difference
Both products work the same basic way: they carry a positive charge that pulls the tiny negatively charged particles together into bigger clumps. What happens next is where they part ways.
| Factor | Pool clarifier | Pool flocculant |
|---|---|---|
| What it does | Makes clumps the filter can catch | Makes heavy clumps that sink to the floor |
| Pump | Stays on | Off while it settles |
| Speed | Usually a few days | Often overnight to 24 hours, then vacuuming |
| Effort | Low: dose and backwash | High: careful manual vacuuming |
| Water loss | Normal backwashing only | Several thousand litres to waste |
| Filter type | Sand, glass or cartridge | Needs a multiport valve with a Waste setting |
Using a pool clarifier
A pool clarifier is the low-effort option for mildly hazy water. It works with your filter, so the filter needs to be in decent shape.
- Test and correct pH and chlorine first.
- Clean the skimmer and pump baskets.
- Backwash if the filter pressure is up. Our backwash guide walks you through it.
- With the pump running, add the label dose for your pool’s litres near a return jet.
- Run the pump continuously and backwash whenever the pressure climbs.
- Give it a few days. Don’t double the dose; overdosed clarifier can keep water cloudy.
Clarifier is also the right choice for cartridge filters and any setup without a Waste position, because it doesn’t leave a layer of sludge that has to bypass the filter.
Would you rather we cleared it?
Our team tests the water, sorts out the filter and clears the pool in one visit where possible. Tell us your pool size and how cloudy it is.
How to floc pool water with a pool flocculant
A pool flocculant is the heavy-duty route for very cloudy or milky water where you can’t see the floor. Liquid polymer flocs and powdered alum are both sold locally. Follow your product’s label, but the pattern is usually:
- Check the water level is near the top of the skimmer, because you’ll lose water later.
- Balance the pH into the range the label gives.
- With the pump running, add the pool flocculant (one liquid floc we checked is dosed at 500ml per 50,000 litres) and let it circulate for an hour or two.
- Switch the pump off and leave the pool completely still, usually overnight. Keep everyone out of the water.
- When a layer of sludge has settled on the floor, set the multiport valve to Waste with the pump off, then start vacuuming slowly.
- Top up with a hose as you go if the level drops near the skimmer.
- Backwash and rinse afterwards, then return to Filter and retest the chemistry.
Wear gloves and eye protection, add the product to the pool water, and don’t combine floc with clarifier, algaecide or chlorine in the same dose. Keep children and pets away while the pool is settling.
Cartridge filter? Don’t use floc. Vacuuming that sludge through a cartridge clogs it immediately, and most cartridge systems have no Waste setting to bypass it. Use clarifier instead.
Vacuum to waste: how much water you’ll lose
When you vacuum to waste, every litre the pump pulls goes out of the waste line instead of back to the pool. That’s the point: the sludge never touches the sand. The catch is the water bill.
Pool guides suggest vacuuming to waste can take out something like 5% to 10% of a pool’s volume. In a 50,000 litre pool that’s roughly 2,500 to 5,000 litres. Cape Town households pay for water in steps, and at the time of writing (October 2026) the 10.5 to 35 kilolitre step was R52.20 per kilolitre including VAT, so the refill shows up on your account.
Cape Town’s water restrictions are a recent memory, and water use rules can tighten again in a drought. Check the City’s current restrictions before you drain and refill. In a dry spell, a clarifier and more filter hours is often the better choice even if it takes longer.
Speed and care with the vacuum matter. Moving the head too fast lifts the floc back into the water and you’re back to square one. Go slowly, overlapping strokes, and stop to let it settle again if it billows up.
Which pool flocculant or clarifier to choose
Use this as a rough guide:
- Slight haze, floor visible: fix the chemistry, backwash, add clarifier and give it a few days.
- Milky water after a shock: wait 24 to 48 hours with the pump on before adding anything. Many pools clear by themselves.
- Floor not visible, sand or glass filter, water to spare: pool flocculant and vacuum to waste.
- Cartridge filter: clarifier only.
- Keeps clouding up every few weeks: look at the filter media. Our guide on how much sand a pool filter needs covers when it’s time to change it.
If the cloudiness has a green tint, you’re dealing with algae as well. Kill it with chlorine first, then see our guide to algaecide for pools to stop it returning. At the time of writing (October 2026), 1kg tubs of alum flocculant sell from around R59 in SA stores, so the product is cheap; the water and the hours of vacuuming are the real cost.
Keeping cloudy pool water from coming back
Once the pool is clear, a few habits stop you reaching for the bottle again. Run the pump long enough each day for the whole pool to pass through the filter at least once. Test pH and chlorine weekly, and more often in hot weather or after a big rainstorm. Backwash when the pressure gauge rises, not on a fixed date.
Net out leaves before they break down, especially after a windy day, and keep the skimmer basket empty so flow stays strong. Our weekly pool maintenance checklist puts those jobs in one place.
Pool flocculant and cloudy water questions
Is pool flocculant better than clarifier?
It’s faster, not better. Pool flocculant clears very cloudy water in about a day but needs the pump off and careful vacuuming to waste. Clarifier takes a few days but works with the pump running and wastes no extra water.
Can you swim in a cloudy pool?
It’s best not to. If you can’t see the floor, you can’t see someone in trouble on the bottom, and cloudy water often means chlorine or pH is off. Wait until the water is clear and the chemistry tests in range.
Can you use clarifier and shock at the same time?
Don’t add them together. Shock first with the pump running, wait until chlorine drops back towards normal, then add clarifier if the water is still hazy. Adding one product at a time is safer and lets you see what worked.
Why is my pool cloudy after adding algaecide?
Usually it’s dead algae in the water, or the algaecide was overdosed. Run the pump, backwash when the pressure rises and give it a day or two. If it stays cloudy, test the water and check the filter.
Can I use floc with a cartridge filter?
No. The settled sludge clogs a cartridge almost immediately, and most cartridge systems can’t vacuum to waste. Use a clarifier instead and clean the cartridge more often while the water clears.
If you’d rather skip the vacuuming, our once-off pool clean covers cloudy water, filter checks and water balancing, and our pool filter repairs team handles valves and filters that aren’t doing their job.
Get your water clear again
Send us a photo of the pool and the filter, and tell us your suburb. We’ll tell you whether it needs a clarifier, a floc and vacuum, or a filter repair.
