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How to use pool flocculant

Updated: 21 October 2026

You are stood at the multiport with a bottle or a cube, and the water is dull rather than green. How to use pool flocculant depends on the label in your hand, not on one add-and-swim routine. Drop granules, a gel cube and a skimmer cartridge do not share a clock, a dose point or a valve position. Test, stay out if you cannot see the floor, then follow one sequence. Product choice stays on the [buying guide](/hub/pool-care/flocculant-pool/sub/flocculant-pool-buying-guide). The [Flocculant pool comparison](/hub/pool-care/flocculant-pool) lists the nine amazon.co.uk products. A qualifying purchase can earn us a commission at no extra cost to you. No pool was dosed.

You are stood at the multiport with a bottle or a cube, and the water is dull rather than green. How to use pool flocculant depends on the label in your hand, not on one add-and-swim routine.

Our top picks

Bayrol Bayrol Superflock Plus, 1 kg

Best overall

Bayrol Bayrol Superflock Plus, 1 kg
9.2/10about £22.02
View offer
Mineralsi Jolly Gel flocculent, 8 cubes

Alternative

Mineralsi Jolly Gel flocculent, 8 cubes
9.2/10about £24.99
View offer
Blue Horizons Blue Horizons granular floc, 2 kg

Alternative

Blue Horizons Blue Horizons granular floc, 2 kg
9.0/10about £18.91
View offer
On this page
  1. 1.Before any product goes in
  2. 2.Drop floc, two clocks
  3. 3.Gel cube and skimmer cartridge
  4. 4.Getting waste water out

Before any product goes in

Test chlorine and pH against the label in your hand. Blue Horizons' shop page asks for pH 7.2–7.6. Lo-Chlor's Maxi-Floc Plus sheet, a different product, asks for pH 7.8–8.0. Copying one band onto the other bottle is how a dose fails. PWTAG says cloudiness is often low chlorine, a stopped pump or high pH. If you cannot see the deep-end floor, do not swim. Turn the pump off before you move a multiport valve. Do not mix concentrated chlorine and acid. A flocculant does not kill algae. If someone is ill and the floor is invisible, or if sand is returning, call a pool engineer. The flocculant versus clarifier page is the check if the bottle might not be a floc.

Drop floc, two clocks

Blue Horizons is the sand-only example. Pre-dissolve at most 100 g per 10 litres and add it on recirculate. The shop page says about 30 minutes, then 12–24 hours before you vacuum to waste. The amazon lines do not print that wait, so the leaflet wins if it is shorter. If it has not worked, retest rather than tip in a second tub. Maxi-Floc Plus, not a product in this set, says 1–2 hours then about six hours, at a different pH. Do not blend the waits. Quickflock Super is 100–200 ml over the skimmer and 15 minutes, then filtration, not a floor vacuum. Cartridge pools belong on the sand-filter page.
Bayrol Bayrol Superflock Plus, 1 kg

Testsieger

Bayrol Bayrol Superflock Plus, 1 kg
9.2/10about £22.02
View offer

Gel cube and skimmer cartridge

Jolly Gel goes in the pump basket, not the skimmer and not beside chlorine tablets. One cube, on sand, glass or zeolite. Cut it if a whole block will not fit. If it is still there after two days, it missed the flow. Do not add a second cube. Backwash when the pressure rises in the first hours. Superflock Plus goes in the skimmer after a backwash, on sand or glass, one cartridge up to 50 m³. The about £22.02 listing is the best value and only says to place it in the skimmer. HTH Regularfloc is 10 sand-filter cartridges without that volume. Neither sock is a reason to vacuum the floor.

Getting waste water out

Vacuum to waste only when the label says the debris is on the floor. Pump off, multiport to waste, prime, then vacuum slowly. Letts says refill before the skimmer sucks air. Then pump off, valve to filter, pump on, top up, and retest, because waste water took treated water with it. Filter mode during that vacuum sends the floc back through the sand. Recirculate spreads the dose. It is not the clean-up. If it is still cloudy the next day, check the valve and the chemistry before a second dose.

Common questions

Do I turn the pump off?
Yes, before you move the multiport. Letts and 1st Direct Pools both start the waste setting with the pump off. You turn it on again once the valve is seated, whether you are recirculating a fresh dose or vacuuming to waste. Leaving it running while you twist the handle is what damages the valve. Turn it off again before you return the valve to filter.
Should the valve be on filter, recirculate or waste?
Recirculate while you spread a drop floc such as Blue Horizons. Waste when you vacuum the settled layer, with the pump off as you change position. Filter is the normal running mode afterwards, and it is where a skimmer cartridge such as Superflock Plus works. Filter is the wrong mode for vacuuming a drop floc, because the dirt goes back through the sand.
How long do I wait?
There is no shared wait. Blue Horizons' shop page says about 30 minutes of recirculation and 12–24 hours to settle. Maxi-Floc Plus, a different brand, says 1–2 hours of running and about six hours. Quickflock Super's lines say 15 minutes, then filtration, not an overnight settle. Jolly Gel's lines say a few hours, and reviewers still backwash. Use the clock on your packet.
Where does a Jolly Gel cube go?
In the pump basket, in the flow, not in the skimmer and not next to chlorine tablets. Cut it if a whole cube will not sit in a basic basket. One cube is the maker's dose, on sand, glass or zeolite. If it is still intact after a couple of days, it missed the flow. Backwash when the pressure rises.
Where does a Superflock cartridge go?
In the skimmer, after a backwash, on a sand or glass filter. Bayrol's sheet allows one cartridge up to 50 m³ and a pH around 7.0–7.4. HTH Regularfloc also names a sand filter and does not print that volume. It does not go in a cartridge filter, and it does not replace a waste vacuum.
What if I have already run floc through the filter?
Backwash before you add a second dose. Chemicals for Pools notes that too much floc can stick the media, and that a backwash about a day later is part of the routine. If the pressure is high and the water is milkier, the bed is loaded. Vacuuming on filter will not remove what is already in the sand. If sand is returning, stop and call someone who can open the filter.

Related pages

Best pool flocculant

Flocculant pool

How to choose a UK pool flocculant for your filter

Flocculant for a sand filter: what the listings say

Flocculant vs clarifier: which bottle for the pool

Sources

Public UK and maker sources used for this page in October 2026. Shelf prices and star lines are the amazon.co.uk figures for these nine listings, dated 19 October 2026.

  1. HSE: Swimming pools (retrieved 21 October 2026)
  2. HSE: GB CLP (retrieved 21 October 2026)
  3. PWTAG: Cloudy water technical note (retrieved 21 October 2026)
  4. PWTAG: Code of Practice (retrieved 21 October 2026)
  5. East Lindsey: Small swimming pools guidance (retrieved 21 October 2026)
  6. Bayrol: Superflock Plus data sheet (retrieved 21 October 2026)
  7. Bayrol: Quickflock liquid (retrieved 21 October 2026)
  8. Jolly Gel, Mineral Supplies International (retrieved 21 October 2026)