DIY Ice Bath — Build Guide

The concept

Core principle

You don't touch the refrigerant — that's illegal without an F-gas cert in Switzerland. Instead: coil copper tubing inside the fridge, pump your tub water through the coil, fridge chills it, water returns cold. The fridge becomes a water chiller.

Tub

→

Pump

→

Coil in fridge

→

Back to tub

CLOSED LOOP — WATER CIRCULATES CONTINUOUSLY

What to expect

1

Fill tub with cold tap water (roughly 14°C in Swiss summer)

2

Run the pump loop — a decent fridge pulls water down to 8–12°C in about 2–4 hours

3

Fridge maintains temperature while you use it — pre-cooling with tap water does the heavy lifting

✓ The fridge is a heat exchanger here, not the primary coolant. Always pre-fill with cold tap water — don't expect the fridge to cool from room temp.

Build A — ultra cheap

CHF 50–80 TOTAL

Vessel

Large plastic storage bin 200L+ from Jumbo or Ikea (~CHF 20–30) — or grab a free bathtub off Ricardo.ch. Both work fine.

Parts list

Copper tubing

8–10mm OD, 10–15m. Coils inside the fridge.

CHF 25–35

Aquarium pump

Used from Ricardo.ch. Any 300–600 L/h model.

CHF 5–15

Hose connectors

Garden type + hose clips. Connects pump to tubing.

CHF 5–10

Foam board

Baumarkt offcut. Wrap around the tub.

CHF 5

Estimated total CHF 40–65

✓ You already have the fridge — that's the expensive part of any commercial chiller. This build is just the loop around it.

Build B — proper setup

CHF 250–500 TOTAL

Vessel

300L galvanized stock tank from Landi (CHF 80–120) — proper size, durable, looks clean. The standard choice for serious builds.

Cooling options — pick one

Option 1

Aquarium chiller — CHF 150–200 used

JBL CristalProfi or Hailea unit off Ricardo.ch. Plug-and-play — just hook into a pump loop. Holds exact temp reliably, quiet, built for this use case.

Option 2

Window AC unit conversion — CHF 80–150 used

Route the AC evaporator coil into a sealed insulated box filled with water. Pump circulates tub water through that box. More powerful than a fridge — gets you to 5–8°C more easily.

Additional parts

Submersible pump

500–1000 L/h flow rate

CHF 20–30

PVC/silicone hose

2m length, matching pump diameter

CHF 10

Pipe insulation

Foam sleeve for connecting lines

CHF 8

Thermostat outlet

Auto-cycles pump. Jumbo, ~CHF 15

CHF 15–25

Fridge coil install

✓ No drilling needed. Feed through the door gasket — takes about 10 minutes.

Door seal method

1

Coil your copper tubing tightly inside the fridge, leaving ~50cm sticking out at one end

2

Gently pull the door gasket (rubber magnetic strip) away from the edge — it just clips into a channel, no screws on most fridges

3

Press the tubing flat against the door frame and re-seat the gasket over it

4

Close the door — the gasket compresses around the tube and seals reasonably well

5

Wrap the tubing at the exit point in foam pipe insulation or cloth, then add silicone sealant if you want it airtight

! Never drill through the fridge walls. Refrigerant lines run inside them — one wrong hole and the fridge is dead (and you'll breathe refrigerant gas).

Tubing size note

8mm OD tubing fits through most standard fridge door gaskets without issue. 10mm can be tight — if needed, flatten it slightly at the exit point or press it against the frame corner where there's more clearance.

Tips — both builds

❄ Insulate the tub. Foam board or a camping sleeping mat duct-taped around the sides cuts heat gain by ~40%. Cover the surface too — most heat enters from the top.

↓ Fill at night. Air temperature is lower, so the fridge has less ambient heat to fight. You'll reach target temp faster.

⚡ Thermostat outlet (CHF 15 at Jumbo) cycles the pump automatically when the water rises above your set temp. Don't run the pump 24/7.

→ Target temp: 10–15°C is the range for cold exposure benefits. Sub-10°C is advanced — start at 15°C and work down over weeks.

→ Session length: 3–10 minutes at 10–15°C is the typical range. Get out before shivering becomes uncontrollable. Never go in alone the first few times.