Cloudy water is full of particles so fine they pass straight through the filter. Both flocculant and clarifier clump them together so they can be removed. The difference is who removes them: with a clarifier, the filter; with a flocculant, you vacuum them off the bottom.
Who takes the dirt away?
First: find the cause
Neither of them fixes pH that's out of control, low chlorine or a filter in poor condition. Test pH and free chlorine first, check the filter and backwash. If the water is still cloudy after 24-48 hours of filtration, then go ahead.
The differences
| Clarifier | Flocculant | |
|---|---|---|
| What it does | Groups particles into slightly larger ones the filter can trap. | Binds them into heavy clumps that sink to the bottom. |
| Filtration | Running the whole time. | Switched off after spreading it. |
| Who removes the dirt | The filter. | You, vacuuming the bottom to waste. |
| Filter type | Any, including cartridge. | Sand or glass. Not for cartridge filters. |
| When to use it | Slight cloudiness or dull water. | Very cloudy water, when you need speed. |
How to use a clarifier
- Bring the pH into the recommended range (7.2-7.6).
- Add the dose on the label for your volume, spread around the pool or through the skimmers, with the pump running.
- Filter continuously for 24-48 hours.
- Backwash when the filter pressure rises.
How to use a flocculant
- Bring the pH into the recommended range.
- Spread the flocculant and leave the pump running for a while, as the manufacturer states, so it mixes in.
- Switch the pump off and leave the pool still, usually for 12 to 24 hours, until the clumps settle on the bottom.
- Vacuum the bottom very slowly with the multiport valve on "waste", so the dirt goes out without passing through the filter. If you go fast, the cloud rises again.
- Top up the lost water, backwash and filter normally again.
There is also flocculant in cartridges or tablets that sit in the skimmer and work with the filtration running: they act more gently and slowly, more like a clarifier.
Frequently asked questions
Can I use flocculant with a cartridge filter?
It isn't advisable: the clumps clog the cartridge straight away. With a cartridge filter, use clarifier.
Why is it still cloudy after flocculant?
It may have been vacuumed too fast, vacuumed to the filter instead of to waste, or the cause was something else, such as high pH or low chlorine. Check the readings and the filter before repeating.
Can I swim with clarifier in the water?
At the correct dose and with readings in range, yes. With flocculant, wait until the bottom has been vacuumed and the water is clear.