Cold plunge tub buying guide for UK homes
A cold plunge tub is a tub of cold water you sit or stand in for a short time. Prices run from a few hundred pounds for a basic inflatable to well over a thousand once a chiller and filtration are added. The big differences are not styling but insulation, whether the water is chilled, and how the water is kept clean.
This guide explains what to compare, using published specifications checked on 12 November 2026. We have not tested any tubs. We do not make health claims, and we do not tell you what temperature to use, because that is a decision to take with your own doctor. The safety section below sets out what UK organisations say about cold water.
The short answer
Decide first how you will keep the water cold. A simple insulated tub with an insulated lid relies on ice or cold tap water and holds its temperature for a limited time. A tub with a chiller holds a set temperature and usually includes filtration, but costs more, needs power and needs a base that can carry the weight of the water. Then check size, insulation, water treatment and power before you compare prices.
Types of cold plunge tub
| Type | Published example | Key specifications |
|---|---|---|
| Portable insulated tub, no chiller | Outsunny portable cold water therapy tub (B&Q listing) | 300 litres; 85 cm outer diameter x 75 cm high (inside 75 cm x 73 cm); 2.9 kg; inflatable thermal cover with "insulated time approximately 1 hour"; no chiller mentioned; listed out of stock |
| Inflatable tub with optional chiller | Pro-Line Direct inflatable ice bath | Three sizes: 135 x 80 x 65, 150 x 80 x 65 or 170 x 80 x 65 cm; drop-stitch PVC, 80 mm thick; 13 to 19 kg; £497.40; chiller (0.6 to 1.0 HP, WiFi) is an optional extra, giving 3°C to 42°C control; page showed variants unavailable |
| Rigid tub with chiller and filtration | LUMI Therapy Pro Duo with Cube Pro chiller | 500 litres; 160 x 95 x 67 cm; 1,400 W chiller; minimum water temperature 2°C; multi-stage filtration plus ozone treatment; £1,698; listed as sold out |
These are examples of what exists and how manufacturers describe it. They are not recommendations, and stock and prices change.
What to compare
Size and internal dimensions
Look at inside dimensions as well as outside. The Outsunny tub is 85 cm across on the outside but 75 cm inside, and 73 cm deep inside. If you are tall, or want to share, check whether you can sit comfortably with the water at the depth you want. A two-person tub is a different size class from a one-person tub.
Insulation and lid
The Outsunny listing says its thermal cover gives approximately one hour of insulation, so do not assume an insulated lid holds a temperature for days. The inflatable tub above claims "exceptional durability, insulation, and structure" without giving a rating. If insulation matters to you, ask the seller for a number, such as how many degrees the water gains in 24 hours with the lid on.
Chiller: power and minimum temperature
A chiller is a refrigeration unit that circulates and cools the water. Compare:
- Electrical rating in watts. The LUMI chiller is stated at 1,400 W. The Pro-Line chiller is quoted in horsepower, which does not tell you the electrical draw; ask for the wattage.
- Minimum water temperature. 2°C for the LUMI, 3°C for the Pro-Line tub with chiller. Most home users will not go that low, but it shows the system has headroom.
- Plug and supply. The LUMI page lists the chiller input as 220 to 240 V AC but does not state a plug type. Ask, and have any outdoor socket fitted by a qualified electrician.
Filtration and water treatment
Still water in a garden tub needs managing. The LUMI system includes washable hair and particle filters, a 20 micron filter, a 40 micron washable filter and an ozone treatment, according to its page. The Pro-Line inflatable listing mentions only an optional hot and cold chiller pump. Ask every seller what filtration and sanitising are included, how often to change the water, and what the filters cost to replace.
Weight and where it goes
Water weighs about 1 kg per litre (a standard rule used by Hydropool in its weight planning). So a 300 litre tub holds roughly 300 kg of water, and a 500 litre tub roughly 500 kg, before you add the tub and a person. A person adds more on top (Hydropool uses an average of 185 lb, about 84 kg, for planning).
Put the tub on a flat, level surface that can bear the load: concrete or a well-built paved area, not soft ground. A UK retailer recommends a concrete pad of at least 10 cm for hot tubs, and the same logic applies to heavy water tubs. If you plan a deck, ask a specialist decking installer or structural engineer, as a retailer notes a hot tub needs more joists than a normal deck. Our hot tub base and placement guide explains the sums.
Also plan how to empty the tub. 300 litres is a lot of water to move by bucket, and a drain or hose route makes life easier.
Running costs: the maths
At the Ofgem cap of 26.32p per kWh (1 October to 31 December 2026), a 1,400 W chiller costs 1.4 x 26.32p = 36.8p for every hour it is drawing full power. A chiller does not run continuously once the water is at temperature, so these are upper bounds:
| Chiller full-power hours per day | kWh per day | Cost per day | Cost per 30 days |
|---|---|---|---|
| 2 | 2.8 | 74p | £22.10 |
| 4 | 5.6 | £1.47 | £44.21 |
| 8 | 11.2 | £2.95 | £88.42 |
These are calculations, not measurements. A tub with no chiller has no running electricity cost, but you pay in effort and in the cost of ice, and the water warms back up quickly with the lid off. Filters, sanitiser and water replacement are extra on any tub.
Safety: what UK organisations say
This is general information, not medical advice.
- The RNLI says the effect of water at 15°C and below is often underestimated, that cold water can take your breath away and leave you unable to act within seconds, and that dips should last only a few minutes. It advises entering gradually, wetting your arms, neck and face first, and not dipping alone. Although the RNLI writes about open water, the cold shock response is triggered by the cold, and you should not assume a garden tub is exempt.
- The British Heart Foundation says cold shock can raise heart rate and blood pressure, may increase the risk of abnormal heart rhythms and possibly cardiac arrest, and recommends checking with your doctor or nurse before starting if you have a heart condition.
- Have a second person nearby at first, and never use alcohol before a plunge. (The second point is general safety advice, not from the sources above.)
Keep any power supplies well away from the water and have the outdoor wiring done by a qualified electrician. The IET's guidance for hot tub supplies calls for a 30 mA RCD on the supply; ask your electrician what is appropriate for yours.
Cold plunge buying checklist
- Decide how you will keep the water cold: ice, tap water, or a chiller.
- Check inside dimensions and depth, not just the outside.
- Ask for a real insulation figure, not just a claim.
- If there is a chiller: wattage, minimum temperature, plug type and noise.
- Check filtration, sanitising and filter replacement costs.
- Work out the full weight and the base.
- Plan electrics and drainage.
- Check the return policy, as bulky items are costly to send back.
Frequently asked questions
Do I need a chiller for a cold plunge?
Not necessarily. A tub with an insulated lid and ice can work, but the lid on the example we checked is rated at about an hour. A chiller holds the water at a set temperature, which is more convenient if you plunge often.
How cold should the water be?
We cannot give a safe temperature for you. Chiller tubs we reviewed go down to 2 to 3°C, but the RNLI says water at 15°C and below carries a risk of cold shock, and recommends short dips. Speak to your doctor, especially if you have a heart or blood pressure condition.
How much does a cold plunge tub cost to run?
For a 1,400 W chiller, no more than 36.8p an hour at full power on the current price cap. See the table above.
Can I leave a cold plunge tub outside in winter?
Check the manufacturer's instructions. The pages we reviewed did not state frost protection or winter storage for the tubs listed, so ask the seller before you buy.
Related guides: garden sauna vs indoor infrared sauna.
Sources (checked 12 November 2026)
- B&Q, Outsunny portable cold water therapy tub: diy.com
- Pro-Line Direct, inflatable ice bath tub: prolinedirect.co.uk
- LUMI Therapy, Pro Duo ice bath with Cube Pro chiller: lumitherapy.co.uk
- RNLI, cold water dipping safety advice: rnli.org
- British Heart Foundation, cold water swimming and your heart: bhf.org.uk
- Hydropool, what a hot tub weighs (1 litre is about 1 kg): hydropoolhottubs.com
- Happy Hot Tubs, best base for a hot tub (10 cm concrete, decking joists): happyhottubs.co.uk
- IET, domestic electrical supplies to hot tubs (30 mA RCD): electrical.theiet.org
- EDF, energy price cap 1 October to 31 December 2026 (26.32p/kWh): edfenergy.com