Put a cold plunge on a level, solid surface that can carry its full filled weight, close to a suitable socket and a place to drain it, with clear airflow around the chiller and a route in that it will actually fit through. Because one litre of water weighs about one kilogram, a filled plunge with someone in it can weigh several hundred kilograms, so a ground floor slab or patio is usually best and anything else should be checked by a structural engineer.
This guide is part of our cold plunge setup and care hub.
Step 1: work out the filled weight
The empty weight on a spec sheet is only the start. Add the water and the person using it:
Filled weight = empty weight + litres of water (1 litre is about 1kg) + the user's weight
Then divide by the footprint to see how concentrated that load is. The examples below are illustrative; your actual fill level and body weight will change the numbers.
| Example | Footprint | Approximate load |
|---|---|---|
| ThermoX Elite: 113kg empty, plus 300 litres of water, plus an 80kg user | 1950 x 800mm, about 1.56m² | About 490kg in total, roughly 315kg per square metre |
| ThermoX Pro: 700 litres at full capacity plus an 80kg user, before adding the tub's own weight | 1700 x 750mm, about 1.28m² | About 780kg or more, over 600kg per square metre |
| ThermoX Core: every 100 litres of water | 1000 x 1000mm, 1m² | Adds about 100kg per square metre |
Those numbers are why location matters. A filled plunge can weigh as much as several adults standing shoulder to shoulder in one small area, and it stays there all the time, not just for a few minutes.
Step 2: choose a suitable floor
Usually the simplest options
- Ground floor concrete slab: garages, utility rooms, plant rooms and many ground floor extensions.
- Patio or concrete base outdoors: level, sound and laid on a properly prepared sub-base.
Ask a structural engineer first
- Suspended timber ground floors, common in older UK homes
- Any upper floor, including bedrooms and loft rooms
- Balconies, roof terraces and flat roofs
- Raised decking, where the load sits on joists and posts
- Garden rooms and sheds built on timber bases
Domestic floors are generally designed for everyday loads such as furniture and people moving around, rather than a concentrated, permanent load of half a tonne or more. A structural engineer can assess the joists, spans and supports and tell you whether strengthening is needed. It is a modest cost compared with repairing a damaged floor or ceiling.
Level matters too
A plunge should sit level so the load spreads evenly and the water line sits correctly. Avoid soft ground, gravel without a firm base, and lawns, which can settle unevenly over time.
Step 3: check the route in
Many installations are decided by the delivery route rather than the final spot. Measure every point the plunge has to pass:
- Door and gate widths, with doors fully open
- Hallway turns and tight corners
- Steps, stairs and changes in level
- Side passages, bins, low branches and overhead obstacles
Compare those with the product dimensions, allowing extra for packaging and for the people carrying it. The ThermoX Elite measures 1950 x 800 x 710mm and weighs 113kg empty, so plan for several people to move it. The ThermoX Pro tub is 1700 x 750 x 580mm with a separate chiller of 60 x 40 x 47.5cm. The ThermoX Core is a compact 1000 x 1000 x 990mm. All our plunges come with free UK delivery, and our team can talk through access before you order.
Step 4: plan power, drainage and airflow
Power
Place the plunge within reach of a suitable socket so you do not need an extension lead. Larger models may need a dedicated 13A outlet, ideally on a dedicated circuit, and any outdoor socket should be weatherproof and RCD protected. Read cold plunge electrical requirements in the UK before you decide.
Drainage
Work out where several hundred litres of water will go when you change it. A floor drain, outside gully or short hose route makes water changes far easier. If you use a chemical sanitiser, do not drain into ponds, streams or surface water drains that lead to watercourses.
Airflow
A chiller removes heat from the water and releases it into the surrounding air. Keep its vents clear of walls, fences and planting, and avoid tight, unventilated cupboards. A plunge with an external chiller also needs space beside the tub for the unit and a tidy hose run.
Step 5: think about daily use
- Shower nearby: showering before each plunge keeps the water cleaner, so a short walk from a shower is ideal.
- Safe surround: a non-slip surface to stand on and space to dry off.
- Shade: outdoors, direct sun warms the water and makes the chiller work harder.
- Debris: keep away from overhanging trees where possible, and always use the cover.
- Ventilation: indoors, choose a room with an extractor or opening window to manage moisture.
- Privacy and lighting: especially for early mornings and winter evenings.
Still deciding between inside and out? Our guide on choosing an indoor or outdoor cold plunge compares the two, and Using a Cold Plunge in a UK Winter covers frost protection for outdoor setups.
Location checklist
| Check | Good sign |
|---|---|
| Floor | Ground floor slab or patio, or an engineer has approved it |
| Level | Flat and firm, no soft ground |
| Access | Every door, gate and corner measured |
| Power | Suitable socket within reach, RCD protected |
| Drainage | Clear plan for emptying the tub |
| Airflow | Chiller vents unobstructed |
A quick safety note
Speak to your GP before cold plunging if you have a heart condition, high or low blood pressure, are pregnant or have any other medical condition. Never plunge after drinking alcohol, and avoid plunging alone. The RNLI warns that cold water shock is real: water below 15°C can trigger gasping and a sharp rise in heart rate and blood pressure. Start warmer and shorter.
Frequently asked questions
How much does a filled cold plunge weigh?
Add the empty weight, the water and the user. One litre of water weighs about one kilogram, so 300 litres adds about 300kg. For example, a ThermoX Elite at 113kg empty with 300 litres of water and an 80kg user comes to roughly 490kg.
Can I put a cold plunge upstairs?
Only after a structural engineer has assessed the floor. Upper floors, suspended timber floors, balconies and decking may not be designed for a concentrated, permanent load of several hundred kilograms, so they need checking.
Can a cold plunge go on decking?
Possibly, but decking spreads the load through joists and posts that may not be designed for it. Ask a structural engineer, or use a level concrete base or patio instead.
How much space do I need around a cold plunge?
Allow room to step in and out safely, a non-slip area to dry off, access to the filter and controls, and clear space around the chiller's vents so it can move air freely. Check your manual for specific clearances.