Chlorine float for a hot tub
Updated: 23 October 2026
You have a hot tub, not a 40 m³ pool, and you are deciding whether a garden dosing float is the right dispenser. A family tub can use a small 20 g float and a test. A tub you let to paying guests needs the inline feeder that HSE guidance HSG282 describes. Heat and a few hundred litres change the dose before the plastic shape does. The eleven listings are on the [dosing float comparison](/hub/diy-supplies/dosing-float). Peter F. checked the stored listings, not a lab. A qualifying purchase can earn a commission at no extra cost to you.
You have a hot tub, not a 40 m³ pool, and you are deciding whether a garden dosing float is the right dispenser. A family tub can use a small 20 g float and a test.
You have a hot tub, not a 40 m³ pool, and you are deciding whether a garden dosing float is the right dispenser. A family tub can use a small 20 g float and a test. A tub you let to paying guests needs the inline feeder that HSE guidance HSG282 describes. Heat and a few hundred litres change the dose before the plastic shape does. The eleven listings are on the dosing float comparison. Peter F. checked the stored listings, not a lab. A qualifying purchase can earn a commission at no extra cost to you.
Our top picks
| Badge | Product | Tablet size | Stated places | UK review note | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  Steinbach Steinbach Mini 20 g float | 20 g | Hot tub only as a question | Missing lid; ring spins | 8.8 | about £5.39 | View offer |
 Gre Gre FDP20 20 g float | 20 g | All pool types | Holds tablets; rub mark | 8.6 | about £11.82 | View offer | |
| Alternative |  Jonuin Jonuin turtle floater | 1 inch and 3 inch | Pools and spas | One shell cracked | 8.2 | about £12.99 | View offer |
On this page
Why a hot tub is not a small pool
A hot tub holds much less water than a garden pool, and it holds it hot. A tablet that is a gentle dose in a large pool can push a spa reading up in an afternoon. Happy Hot Tubs tells you to use 20 g tablets, about 1 inch in their wording, and to treat a 200 g pool puck as the wrong object.
Chlorine tablets still have a UK how-to for tubs. You pick one chemistry. Steinbach’s file only raises hot tubs as a question. The Jonuin turtle at £12.99, claiming five 3 inch tablets, is a large-pool load.
20 g tablets, and one chemistry
For a family tub, use a small chamber and 20 g tablets. In this set, the Steinbach Mini at £5.39 and the Gre FDP20 at £11.82 are the listings that state 20 g. Happy Hot Tubs says those tablets go in a float, an inline feeder, or a skimmer, and never on the shell. If the reading is high, they suggest lifting the float. That is retailer practice, not a certificate.
Choose chlorine or bromine and stay with it. Happy Hot Tubs’ dispenser sheet bans mixing bromine with chlorine, and trichlor with calcium hypochlorite. If you switch, wash the empty float outdoors and keep the sludges apart. A 200 g pool tablet does not belong in the spa float. NEIQIUWING states 1.5 inch, which is neither the 20 g shop size nor the 200 g puck. The inch-by-inch match is on chlorine tablet size for a floater.
Marks, liners, and taking it out
One United Kingdom review of the Gre FDP20 says the float left a black mark where it rubbed a hot tub. A four-year warranty claim does not erase it. A hard plastic body, left against one patch of shell, can mark acrylic. Move the float. Do not park it in the same corner all weekend. Moving it is a different job from an inline feeder, which doses in the pipework.
PoolPro says slow chlorine tablets and a floater can bleach a vinyl-style liner and cover, and points those owners to granules. Other UK shops sell 20 g floats for hot tubs. Take the float out while anyone is sitting in. Deep Blue’s 20 g label says about 3–5 mg/l in a hot tub, with pH 7.2–7.6. That figure is their label, not a law. The fill order is on how to use a chlorine float.
When the tub is let
If nobody pays to use the tub, HSG282 treats a private spa as outside the Health and Safety at Work etc. Act. A domestic-type spa you let falls under that Act. Paragraph 76 describes disinfection with bromine or chlorine through an inline feeder, a residual even when the tub is empty, and a water-change pattern.
East Ayrshire’s holiday-let FAQ gives free chlorine 3–5 mg/l, bromine 4–6 mg/l, and pH 7.0–7.6. Those numbers are a council explainer, not the same as SureSpa’s 3–5 ppm bromine. A marketplace bullet that names a spa is not an inline feeder. If you let the tub, talk to environmental health about the feeder, the log, and the water changes.
Common questions
Can I put a pool dosing float in the hot tub?
You can put a small 20 g float in a family tub if the tablets are 20 g and you test and lift it out. You should not put a pool puck, or a turtle loaded with 3 inch tablets, into that water. Steinbach’s listing does not give you a spa specification. Gre’s does not either, and one UK review says that float marked a hot tub.
Chlorine tablets or bromine tablets?
Use one. Bromine is the spa default on SureSpa’s 20 g tablets because of temperature, with their page talking about 3–5 ppm once a residual exists. Chlorine tablets still have a UK how-to, including Deep Blue’s 3–5 mg/l hot-tub line on their 20 g product. Never put both in one float.
Will a 3 inch puck fit, and should it?
A 3 inch puck is the large tablet, about 200 g in UK shop wording, and it should not go in a hot tub or in a 20 g mini. Jonuin claims five of them. That claim is a reason to leave the turtle out of a small spa, not a reason to try one puck.
Why did a float leave a mark on the shell?
A UK reviewer of the Gre FDP20 reported a black mark where the float rubbed the hot tub. Hard plastic, left in one place, can mark a shell. The listing does not warn you in the bullets. Move the float, and take it out while you bathe. If the tub has a vinyl-style liner, PoolPro’s separate warning is that slow chlorine tablets and a floater can bleach the liner and cover. Read both.
Is a float enough if I let the tub?
No. A tub you let is a business in HSG282’s terms, and that guidance describes an inline feeder, a residual when the tub is empty, and a water-change pattern. A garden float does not meet that description. East Ayrshire’s holiday-let note gives free chlorine 3–5 mg/l and bromine 4–6 mg/l for that setting. Those are council figures for a let. Speak to environmental health before the first guest.
Related pages
Sources
Public UK sources and the amazon.co.uk listings compared on this page. Updated 22.10.2026.
- HSE: HSG179, Managing health and safety in swimming pools (retrieved 22.10.2026)
- HSE: Swimming pools (retrieved 22.10.2026)
- HSE: HSG282, Control of legionella and other infectious agents in spa-pool systems (retrieved 22.10.2026)
- PWTAG: Code of Practice (retrieved 22.10.2026)
- PWTAG: Technical note 68, swimming pool chemicals (retrieved 22.10.2026)
- Pool Warehouse UK: chlorine tablets 5 kg (retrieved 22.10.2026)
- Consumer Rights Act 2015 (retrieved 22.10.2026)