How to use chlorine tablets in a pool
Updated: 16.10.2026
The lid is already off, and a bullet that said the water would be safe is not a dose. How to use chlorine tablets in a pool, for the tub you actually opened, is a short sequence: read the label, test the water, put the tablet in a feeder that matches it, run the pump, and put the cap back on. If the label is missing or the pump is off, you stop. The seven listings are on the [chlorine tablets for pools](/hub/pool-care/chlorine-tablets-pool) comparison. The Products Compared editorial team based these steps on those amazon.co.uk listings, PWTAG Technical Note 68 and HSE guidance, for 15 October 2026. This is not a dose for a managed public pool.
The lid is already off, and a bullet that said the water would be safe is not a dose.
The lid is already off, and a bullet that said the water would be safe is not a dose. How to use chlorine tablets in a pool, for the tub you actually opened, is a short sequence: read the label, test the water, put the tablet in a feeder that matches it, run the pump, and put the cap back on. If the label is missing or the pump is off, you stop. The seven listings are on the chlorine tablets for pools comparison. The Products Compared editorial team based these steps on those amazon.co.uk listings, PWTAG Technical Note 68 and HSE guidance, for 15 October 2026. This is not a dose for a managed public pool.
Our top picks
| Badge | Product | Where it goes | Tablet size | Tablet type | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  Relax Relax 5 kg multifunction tablets | Not stated on the listing | 200 g (3 inch) | Multifunction | 8.8 | about £26.99 | View offer |
| Alternative |  Deep Blue Deep Blue 5 kg 200 g multifunction tablets | Skimmer, dosing chamber or floater | 200 g | Multifunction | 8.1 | about £28.23 | View offer |
| Best value |  Deep Blue Deep Blue 5 kg 20 g multifunction tablets | Not stated | 20 g | Multifunction | 8.4 | about £21.98 | View offer |
On this page
Read the label before the lid stays off
If the label is missing, or you cannot read the instructions, stop before the tablet goes anywhere. Two reviews of the Bulla kit say the instructions are unclear or in broken English. That is a stop, not a prompt to invent a dose from a different tub. HSE’s SR9 sheet tells you to read the label, replace the cap, and keep the product cool, dry and ventilated.
If you have no free-chlorine reading and no pH reading, you are dosing blind. A garden tub is not a managed pool under PWTAG. Which tub to buy, if you have not opened one yet, is the chlorine tablets buying guide.
Floater, skimmer, or feeder
Put the tablet in a feeder built for that chemical and that tablet size. PWTAG Technical Note 68 says the feeder is only for its own chemical. ChlorineXpress, the Deep Blue stabilised listing and the Deep Blue 200 g multifunction listing name a floater, a skimmer or a feeder. Relax and the Deep Blue 20 g listing do not say where the tablet goes.
SINPY’s tablets go in the 5 inch floater in the box. Bulla’s line that 1 inch tablets can go straight into the pool is a bullet on that kit. Do not copy it onto a 200 g puck. One Deep Blue review warns against leaving tablets in the skimmer when the pump is off. A paddling pool with no pump is a different case, on chlorine tablets for a small pool.
One listing’s dose is not the next listing’s dose
The Deep Blue stabilised listing prints one tablet per 25,000 litres a week, with free chlorine at 1–3 ppm and pH at 7.2–7.6. That text belongs to that label. The pack weight on the same listing is unresolved, so it is not a weekly dose for every tub in the house. Bulla prints seven tablets per 2,500 gallons and does not say which gallon. Do not convert one figure into the other, and do not crush a tablet into boiling water. Multifunction or stabilised changes what else you dose, on multifunction vs stabilised chlorine tablets, and it still does not replace the test.
Dust, a second chemical, and the cap
One Relax review describes split blocks and chlorine dust that irritated the reviewer’s throat. Stop. Do not tip a second chemical in to make up for it. Pool acid does not go in the same bucket. PWTAG Technical Note 68 says not to mix calcium hypochlorite with chlorinated isocyanurates. If you have already combined them, stop.
That is the point where someone who handles pool chemicals for a living takes over. Keep chlorinated isocyanurates below 30°C, closed and dry.
Stop when the label or the pump is missing
Use the place and the dose printed on the tub you opened. Run the pump if that place is the skimmer, and do not leave tablets there when the pump is off. If the label is missing, the instructions are unreadable, or the tub is dusty, stop before the next tablet. A qualifying purchase can earn a commission at no extra cost to you.
Common questions
Should the tablet go in the skimmer or in a floater?
Use the place the label names, and run the pump if that place is the skimmer. ChlorineXpress and both Deep Blue 200 g listings name a floater, a skimmer or a feeder. SINPY and Bulla include a floater. Relax and the Deep Blue 20 g tub do not say, so do not invent a skimmer dose for them.
Can the tablet go straight into the pool?
Only if the label on the tub you opened says so. Bulla’s bullets say the 1 inch tablets can go straight in, and they also include a floater. That line is not a method for a 200 g puck. ChlorineXpress and the Deep Blue 200 g listings name a floater, a skimmer or a feeder instead. If your label is silent, keep the tablet in a feeder made for it.
What dose should I use?
Use the dose on the tub in your hand. Deep Blue’s stabilised label says one tablet per 25,000 litres a week, with free chlorine at 1–3 ppm and pH at 7.2–7.6. The pack weight on that listing conflicts, so the line is not a universal dose. Bulla says seven tablets per 2,500 gallons, without saying which gallon. Do not convert one into the other. If your tub prints no dose, do not borrow one.
What if the tablet is the same size after two days?
Stop before you add more. Bulla reviews describe tablets that do not dissolve, including after two days in the dispenser, and a bucket that barely moved the chlorine reading. If the instructions are unreadable, the next tablet is not the fix. A slow 200 g puck getting smaller is a different observation from a tablet that does not shrink. Do not crush it into hot water.
Can I put pool acid in the same bucket?
No. Keep acid out of the bucket and the floater. PWTAG Technical Note 68 says not to mix calcium hypochlorite with chlorinated isocyanurates. If those have already met, do not add another chemical to balance it. Stop, and hand it to someone who handles pool chemicals professionally. Replace the cap. HSE SR9’s short version is to read the label and put the cap back on.
What do I do with dust in the tub?
Stop. One Relax buyer found split blocks and chlorine dust that irritated their throat. Do not rinse the dust into the pool and carry on. Close the tub, get into fresh air, and do not dose a second product in the same session. If your throat stays irritated, treat that as a health problem rather than a pool problem.
Related pages
Sources
Public UK sources listed in the research digest. Listing prices, stars, and review counts are from the amazon.co.uk capture dated 15 October 2026, not a live re-check.
- HSE — Swimming pool safety management (retrieved 15 October 2026)
- HSE SR9 — Safe use of pool biocides (retrieved 15 October 2026)
- HSE — Biocides regulations (retrieved 15 October 2026)
- HSE — GB CLP classification and labelling (retrieved 15 October 2026)
- PWTAG Code of Practice (retrieved 15 October 2026)
- PWTAG TN68 — Handling and storage of pool chemicals (retrieved 15 October 2026)
- UK Pool Store — What is cyanuric acid (retrieved 15 October 2026)
- Swimming Pool Chemicals — Chlorine tablets (retrieved 15 October 2026)