Yes, you can turn your bath into a cold plunge. The simplest way is to fill it with cold tap water and add ice, and the more consistent way is to use a bath chiller that cools the water to a set temperature and holds it there. Ice is cheap to try but hard to control, while a chiller costs more upfront but gives you the same temperature every session.
This article is part of our cold plunge buying guide. If you are new to the terms, our explainer on cold plunges vs ice baths is a good starting point.
Option 1: cold tap water and ice
Run the bath cold, check the temperature with a thermometer, and add ice until you reach the temperature you want. It needs no equipment beyond ice and a thermometer, which makes it a reasonable way to find out whether cold water suits you.
How much ice do you need?
More than most people expect. Melting a kilogram of ice absorbs about 334 kilojoules of heat, and the meltwater then absorbs a little more as it warms up. Using those figures:
- Cooling a 150 litre bath from 15°C to 10°C takes roughly 8 to 9kg of ice.
- Cooling the same bath from 15°C to 5°C takes roughly 18kg.
These are rough physics estimates that ignore heat coming in from the room, the bath itself and your body, so in practice you may need more. Tap water temperature also changes through the year, so in summer you start warmer and need more ice.
The downsides of ice
- Inconsistent temperature. The water warms steadily as the ice melts and as heat flows in from the room.
- Buying, making and storing ice. Several bags per session add up and need freezer space.
- A fresh fill every time. With no filtration, the water is drained after each session.
Option 2: a bath chiller
A bath chiller is a self-contained cooling unit that sits beside the bath, circulates the water, removes heat and holds a set temperature. Instead of guessing with ice, you choose a temperature and the chiller works to keep it there. Our guide to cold plunge chillers explains how they work and what the numbers mean.
The ThermoX Drop
The ThermoX Drop is designed for exactly this. It is a self-contained chiller that cools the bath you already own, with no plumbing. Key facts:
- 3.5kW of cooling with a temperature range of 3 to 25°C.
- Ozone sanitation plus 20 micron filtration.
- Runs on a UK 220 to 240V supply with a rated power of 1.02kW.
- Measures 41.5 x 39 x 43.6cm and weighs 36.5kg, on locking castors.
- £1,995, with free UK delivery, a 1-year warranty and 30-day returns for unused items in their original condition.
For an idea of electricity costs, see how much a cold plunge costs to run in the UK, which includes worked examples based on the Drop's rated power.
Is your bath big enough?
A standard UK bath is commonly sold at 1700mm long by 700mm wide, but the internal space is smaller because of the sides and the slope at one end. Two things matter for plunging:
- Length. You want to sit with your legs out or slightly bent. In a shorter bath, you may need to bend your knees more.
- Depth. Many baths are shallower than a dedicated plunge tub, so you may need to recline to get the water to your shoulders. Check how high you can fill it before it reaches the overflow.
To estimate volume, multiply the internal length, width and water depth in metres, then multiply by 1,000 for litres. For example, water 1.4m long, 0.5m wide and 0.3m deep is roughly 210 litres. Baths taper, so treat this as a rough figure, but it helps when working out ice quantities or cool-down times.
Safety in the bathroom
Electricity near water
Electrical Safety First notes that your body conducts electricity more easily in wet conditions, increasing the risk and severity of an electric shock. It also says that sockets are generally not allowed in bathrooms unless they are at least 2.5 metres from the edge of a bath or shower tray, that all circuits in or passing through bathrooms now need RCD protection, and that you should not use extension leads to power appliances in a bathroom.
Many UK bathrooms have no sockets at all, so think about where any bath chiller will plug in before you buy. Follow the manufacturer's instructions, never run an extension lead into the bathroom, and speak to a registered electrician if you are unsure. Never improvise with mains-powered equipment near a bath; our article on DIY chest freezer cold plunges explains why.
Getting in and out
The RNLI notes that cold water can seriously affect your breathing and movement. Your hands and legs may feel clumsy after a cold session, and bathroom floors get slippery. Use a non-slip mat, keep a towel and warm clothes within reach, and lower yourself in slowly rather than dropping in.
Your body
The RNLI describes cold water shock, an involuntary gasp and rapid breathing that can follow immersion in water below 15°C, and the British Heart Foundation notes that cold immersion can raise heart rate and blood pressure. Speak to your GP first if you have a heart condition, high or low blood pressure, are pregnant or have any other medical condition. Never plunge after drinking alcohol, avoid plunging alone, and start warmer and shorter than you think you need. Our beginner guide covers your first sessions.
Ice or chiller: which suits you?
If you want to try cold water a handful of times, ice is a low-cost experiment. If you plan to plunge regularly, want a predictable temperature and do not want to buy, store and carry ice, a bath chiller is the more practical long-term option, and it avoids the space and cost of a separate tub.
Frequently asked questions
How much ice do I need to make a cold plunge in my bath?
As a rough guide, cooling a 150 litre bath from 15°C to 10°C takes about 8 to 9kg of ice, and down to 5°C about 18kg. You may need more in practice, as heat flows in from the room and your body.
Can I leave cold plunge water in my bath between sessions?
With ice alone, it is best to drain after each session as there is no filtration. A bath chiller with filtration and sanitation, such as one using ozone and a fine filter, is designed to help keep water clear between sessions, but follow the manufacturer's care guidance.
Is a bath deep enough for a cold plunge?
Often, yes, although many baths are shallower than a dedicated plunge tub, so you may need to recline to get the water to your shoulders. Measure the internal length and the depth up to the overflow before deciding.
Is it safe to use an electrical chiller next to a bath?
Only with equipment designed for the job, used as the manufacturer instructs, on a properly protected supply. Never use extension leads in a bathroom, and speak to a registered electrician if you are unsure about sockets or RCD protection.