How to use chlorine granules
Updated: 21 October 2026
The tub is open, the liner is vinyl, and a scoop of dry granules looks like the quick way to fix a cloudy above-ground pool. How to use chlorine granules starts with a bucket, not a broadcast across the water. You stir until the solids have gone, pour the solution in with the pump or jets running, and use the gram line on the tub you bought. Then you retest before anyone swims. Brand choice stays on the [chlorine granules comparison](/hub/pool-care/chlorine-granules). This page is the method, from UK label guidance and the amazon.co.uk review files on 19 October 2026. A qualifying purchase can earn a commission at no extra cost to you.
The tub is open, the liner is vinyl, and a scoop of dry granules looks like the quick way to fix a cloudy above-ground pool. How to use chlorine granules starts with a bucket, not a broadcast across the water.
The tub is open, the liner is vinyl, and a scoop of dry granules looks like the quick way to fix a cloudy above-ground pool. How to use chlorine granules starts with a bucket, not a broadcast across the water. You stir until the solids have gone, pour the solution in with the pump or jets running, and use the gram line on the tub you bought. Then you retest before anyone swims. Brand choice stays on the chlorine granules comparison. This page is the method, from UK label guidance and the amazon.co.uk review files on 19 October 2026. A qualifying purchase can earn a commission at no extra cost to you.
Our top picks
| Badge | Product | Pack size | Stabilised | Dissolve notes | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  Deep Blue Deep Blue stabilised granules, 5 kg | 5 kg | Yes | No fail in 7 texts | 8.8 | about £22.00 | View offer |
| Best value |  aBalchemy aBalchemy stabilised granules, 1 kg | 1 kg | Yes | n/a | 8.4 | about £8.99 | View offer |
| Alternative |  Zagosa Zagosa chlorine granules, 5 kg | 5 kg | n/a | One review: easily | 7.6 | about £22.30 | View offer |
On this page
Dissolve them before they touch the pool
Clearwater tells you to pre-dissolve granules every time, including when a label allows a direct add once the water is above 20 °C. The chemical goes into water in a clean plastic bucket, and you stir until you cannot see grains. Total Pool’s text for its SP102 stabilised granules says never to place them directly in the pool, because they bleach.
The SP102 sheet lists serious eye irritation and respiratory irritation, and contact with acids liberates toxic gas. A jug that held pH reducer is the wrong jug. If solids remain, leave them in the bucket. CUQOO’s file, 3.3 from 230 reviews, describes grains still solid after a day, marks on vinyl, and one chemical burn from granules left on a hot-tub seat. Those reports belong to that listing, not to every brand.
Fast dissolving on a title is not permission to scatter the powder. Pool Pro’s 2 kg instructions cap a bucket at 100 g per 10 litres, so a large dose is several buckets. Turn the pump or the spa jets on before you pour.
Dose from the label, not from a single chart
UK gram charts do not agree, so a copied figure can double the dose. Pool Pro uses about 2 g per 1,000 litres to raise free chlorine by about 1 ppm. A Clearwater daily line often quoted here is 20 g for 5,000 litres, about 4 g per 1,000 litres. Total Pool’s SP102 label uses 100 g per 10,000 gallons for about 1 ppm. A UK gallon is not a litre. Reading that line as 100 g per 10,000 litres would under-dose. The number on your tub wins.
A 5,000-litre pool that needs about 1 ppm is about 10 g on the 2 g rule and about 20 g on the 4 g rule. Weigh it. A tablespoon is not a unit, and a heaped spoon in a 1,200-litre spa is a pool dose in a small box of water. Keep granules out of a skimmer that already holds tablets. The solution goes into the water with the pump running, not into the same chamber as trichlor. If free chlorine is already inside the label’s band, another scoop only adds cyanuric acid.
Wait, retest, and stop
People get back in when a test, not a clock, says free chlorine is inside the band on the label. For many domestic pool tubs that band is 1–3 ppm. PWTAG’s code for managed pools on chlorinated isocyanurates is 2.5–5 mg/l. Those are different rules. A garden pool follows the tub and a domestic test kit. A club pool follows the commercial code and a trained operator. Bestway’s shock sketch uses about 24 hours, then the same check. If your label prints a shorter wait, that label wins, and you still confirm with a strip or a drop test.
Stop and get help if someone has swallowed granules or the bucket mix: the poison-centre line is on the label. Eyes or breathing after a mix-up with acid or another chlorine is urgent care. A public, school, or club pool is a managed plant. A spa rash that stays after the water is back in range needs a clinician, not another teaspoon.
When to stop
If you can still see grains, they stay in the bucket. You do not add a second scoop to finish the job. If a test is already inside the band on your label, you stop. If the strip is still high after a shock, people stay out until it falls. If eyes, breathing, or a swallowed mix are involved, follow the label’s emergency line. The gram line on the tub you bought beats a chart copied from another brand.
Common questions
Do I have to dissolve the granules first?
Yes. Clearwater says pre-dissolve even when the water is warmer than 20 °C, and Total Pool’s SP102 text says not to place granules directly in the pool because they bleach. Put water in a clean bucket, add the powder, and stir until it has gone. Pour the solution in with the pump or jets on. If you can still see grains, they stay in the bucket.
How many grams per 1,000 litres?
There is no single UK figure. Pool Pro uses about 2 g per 1,000 litres for about 1 ppm. A Clearwater daily line works out near 4 g per 1,000 litres. Total Pool uses 100 g per 10,000 gallons, and gallons are not litres. On a 5,000-litre pool that gap is roughly 10 g versus 20 g. Weigh what your own tub prints.
Can I tip them on the liner if the water is warm?
Warm water does not make a dry pile safe. Labels that allow a direct add above 20 °C are overridden by Clearwater’s pre-dissolve advice and by Total Pool’s bleaching warning. Vinyl marks in CUQOO’s review file came from granules that never dissolved. Broadcast dosing is the method to retire.
When can people get back in?
When a test shows free chlorine inside the band on your label, often 1–3 ppm on domestic pool instructions. Bestway’s shock sketch adds about 24 hours before that test. PWTAG’s 2.5–5 mg/l is the managed-pool code, not an invitation to swim a garden pool at the top of a shock. If the strip is still high, you wait.
What if they have not dissolved after an hour?
Leave the solids in the bucket. Do not pour the slurry onto the pool floor, and do not add a second scoop to finish it. A thick paste is also past Pool Pro’s bucket limit of 100 g per 10 litres. Treat a tub that will not dissolve as a failed pack, and follow the label for disposal.
Should I add granules to the skimmer if tablets are already in it?
Put the dissolved granules into the pool water, with the pump running, and leave the tablets in their floater or basket. Two chlorine products in one wet chamber are a mix, even when the pool can see both forms on different days. Wash the feeder separately if it is due a clean.
What does a chlorine smell mean after dosing?
It means you should test, not that the level is correct. Smell can come from the bucket you just stirred or from chloramines in tired water. A mild smell left one Zagosa reviewer unsure, and they had not tested yet. Read free chlorine and pH, air the room, and add more only if the result is below the label.
Related pages
Sources
Public UK sources used for this page in October 2026. Shelf prices and star lines are the amazon.co.uk figures for these eight listings.
- HSE: Swimming pools (retrieved 21 October 2026)
- HSE: Biocides, product type 2 (retrieved 21 October 2026)
- PWTAG: Code of Practice (retrieved 21 October 2026)
- Total Pool: SP102 stabilised chlorine granules safety data sheet (retrieved 21 October 2026)
- BISHTA: Water treatment (retrieved 21 October 2026)
- Hydrospares: The facts about stabilised chlorine granules (retrieved 21 October 2026)
- Clearwater: Why pre-dissolve granules (retrieved 21 October 2026)
- PoolStore: What is available chlorine? (retrieved 21 October 2026)