Flocculant for a sand filter
Updated: 21 October 2026
A sand filter still lets the finest dirt through, which is why the water can look cloudy when the chlorine is already in range. A flocculant for a sand filter makes those fines large enough for the sand to hold, or heavy enough to vacuum to waste. Glass counts only when the label names glass. A cartridge or fibre balls are the reason to stop. The [Flocculant pool comparison](/hub/pool-care/flocculant-pool) holds every form. A qualifying amazon.co.uk purchase can earn us a commission at no extra cost to you. Shelf prices are from 19 October 2026. We did not open your filter.
A sand filter still lets the finest dirt through, which is why the water can look cloudy when the chlorine is already in range.
A sand filter still lets the finest dirt through, which is why the water can look cloudy when the chlorine is already in range. A flocculant for a sand filter makes those fines large enough for the sand to hold, or heavy enough to vacuum to waste. Glass counts only when the label names glass. A cartridge or fibre balls are the reason to stop. The Flocculant pool comparison holds every form. A qualifying amazon.co.uk purchase can earn us a commission at no extra cost to you. Shelf prices are from 19 October 2026. We did not open your filter.
Our top picks
| Badge | Product | Filter named | Dose point | How you finish | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  Bayrol Bayrol Superflock Plus, 1 kg | Sand or glass (sheet) | Skimmer after backwash | Backwash | 9.2 | about £22.02 | View offer |
| Alternative |  HTH HTH Regularfloc, 10 cartridges | Sand | Skimmer cartridge | Backwash | 9.2 | about £22.84 | View offer |
| Alternative |  Blue Horizons Blue Horizons granular floc, 2 kg | Sand only | Pre-dissolve, recirculate | Vacuum to waste | 9.0 | about £18.91 | View offer |
On this page
What the sand has to do
Sand is a depth filter. Finer dirt passes until it clumps. Chemicals for Pools says floc makes those fines big enough to trap, you backwash about a day later, and too much floc sticks the media. A domestic pool is dosed by hand, outside the public-pool code.
A drop floc such as Blue Horizons ends on waste, not on filter. A skimmer cartridge ends with a backwash. If the multiport has neither, these products do not fit. Letts says the pump stays off while the valve moves to waste. The valve sequence lives on the how to use pool flocculant page.
Listings that name sand
Blue Horizons, 2 kg at about £18.91, prints sand filters only: pre-dissolve at most 100 g per 10 litres, then vacuum to waste. That is a drop floc, not a weekly sock. The shop page adds a 12–24 hour settle at pH 7.2–7.6, which the amazon lines do not print, so the leaflet wins if they differ.
HTH Regularfloc, about £22.84, is 10 cartridges for a sand filter, then a backwash, not a floor vacuum. Quickflock Super, about £20.50, names sand in the title: 100–200 ml over the skimmer, then 15 minutes. Several UK reviews say there were no English instructions. HTH rapidfloc does not name sand. Do not add it because the brand also sells Regularfloc.
Listings that need the maker's sheet
Superflock Plus is the awkward case. About £22.02, the best value of the two kilos, says skimmer and does not say sand. About £47.78 does not say sand either, and it prints 29.57 ml beside a 1 kg title. Bayrol's sheet says sand or glass, not cartridges, one cartridge up to 50 m³, after a backwash. That sheet is why it can belong here.
Jolly Gel, about £24.99, does not say sand on the amazon lines. The maker's page does: pump basket, sand, Zeoclere or glass, not a cartridge. Glass counts for Superflock Plus and Jolly Gel, not for Blue Horizons, which says sand only. The buying guide is the form choice once the media is allowed.
Cartridge, fibre balls and hot tubs
Intex says flocculant is not recommended with its cartridge pumps because the cartridge clogs. Magnum Filters says most flocs can affect a cartridge warranty unless you can send water to waste. PoolPro points liquid clarifiers at cartridges and jelly or tablet flocculants at sand. A Bestway-style cartridge pump is the stop, not a smaller dose of Blue Horizons.
Fibre balls failed in a UK review of the clarifier cubes: filtration stopped until the balls were washed. Nortembio at about £11.95 names spas and does not name sand. A UK reviewer reported floating slime in a hot tub. The 3.9 from 789 is the widest sample here and the weakest stars. If the bottle might be a clarifier, the versus page is the fork. Call a professional if sand is returning, if you mixed acid and chlorine, or if the pool is a club, school or holiday let.
Common questions
Is a sand filter enough, or do I also need a waste setting?
You need both for a drop floc. Sand catches what the floc has enlarged, and the waste line removes a sunk layer or lets you backwash a loaded bed. Blue Horizons is the vacuum-to-waste example. Superflock Plus and Regularfloc are the backwash examples. A sand filter with no way to dump water cannot finish either routine.
Does glass media count?
It counts for Superflock Plus and for Jolly Gel, because those maker pages name glass. It does not count for Blue Horizons, whose listing says sand filters only, or for HTH Regularfloc, whose line says a sand filter. Quickflock Super's title also says sand, not glass. If your filter is glass, use a sheet that says glass, and still backwash.
What about filter balls?
Leave them out. A UK review of the unnamed clarifier cubes said fibre-ball filters stopped until the balls were washed. Jolly Gel's maker excludes cartridge and diatomaceous-earth filters, and fibre balls are the same mismatch: no sand bed to hold the floc. Washing the balls after a failed dose is a recovery, not a method.
Can I floc an above-ground cartridge pool?
No. Intex says not to use flocculant with its cartridge pumps because the cartridge clogs. Magnum ties the same warning to the warranty if you cannot send water to waste. An above-ground pool with a real sand filter is a different machine. The plastic wall does not matter. The filter media does.
Which kept listings actually say sand?
Blue Horizons says sand filters only. HTH Regularfloc says a sand filter. Quickflock Super says sand in the title. Superflock Plus and Jolly Gel need the maker's sheet, because the amazon lines do not say sand. HTH rapidfloc, the unnamed cubes and Nortembio do not say sand. The about £47.78 Superflock listing does not say sand either.
Will floc void a cartridge warranty?
It can. Magnum Filters says most flocculants are incompatible with cartridge filters and may void a warranty unless the water can go to waste. Intex's support page tells cartridge owners not to use flocculant. If the filter is a cartridge, treat the products in this comparison as the wrong chemical.
Related pages
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.
- HSE: Swimming pools (retrieved 21 October 2026)
- HSE: GB CLP (retrieved 21 October 2026)
- PWTAG: Cloudy water technical note (retrieved 21 October 2026)
- PWTAG: Code of Practice (retrieved 21 October 2026)
- East Lindsey: Small swimming pools guidance (retrieved 21 October 2026)
- Bayrol: Superflock Plus data sheet (retrieved 21 October 2026)
- Bayrol: Quickflock liquid (retrieved 21 October 2026)
- Jolly Gel, Mineral Supplies International (retrieved 21 October 2026)