How to Build a Stock Tank Cold Plunge (Step-by-Step)

The most popular DIY cold plunge vessel

The Rubbermaid stock tank cold plunge is the most popular DIY build for good reason: $130 vessel, food-safe plastic, structurally rated for a person's weight, fits through standard doorways, and has the largest accessory ecosystem of any plunge vessel. This guide walks through the complete build, start to finish.

Parts list

Build steps

Step 1: Position the stock tank

Place your stock tank on a level, load-rated surface. Remember: 50 gallons of water + your body weight = about 500 lbs. Concrete floors, reinforced decks, and ground-floor rooms are fine. Second-story rooms may not be. Avoid direct sunlight (UV degrades the plastic over time and adds heat load).

Step 2: Install bulkhead fittings

If you're using a chiller, you need two ports through the tank wall: a suction port near the bottom (about 4" above the floor of the tank) and a return port near the top (about 4" below the rim). Use a 1-1/4" hole saw to drill clean holes, then install 3/4" NPT bulkhead fittings with food-safe silicone on both sides of the tank wall. Let cure 24 hours before filling.

If you're starting with ice only (no chiller), skip this step — you can add fittings later when you upgrade.

Step 3: Add insulation (highly recommended)

An uninsulated stock tank loses 4–6°F of cold per day. Insulated, it loses 1–2°F. That's the difference between a chiller running 4 hours/day vs 12 hours/day. Wrap the sides and bottom of the tank in 2" XPS rigid foam board, sealed with reflective tape. Add an insulated cover on top — most heat loss is through the water surface.

Step 4: Plumb the chiller

Connect your chiller to the bulkhead fittings using 3/4" flexible PVC spa hose. Mount the chiller at or below the waterline of the tank (gravity-fed suction). Add a check valve on the suction line to prevent backflow. Seal all threaded connections with food-safe silicone — never pipe dope or Teflon tape.

Step 5: Wire the temperature controller

If your chiller doesn't have a built-in thermostat, install an Inkbird ITC-308. Plug the Inkbird into the wall, plug the chiller into the Inkbird's "Cooling" socket, drop the probe into the tank (mid-depth, away from the chiller return jet). Set your target temperature, set the compressor delay to 3 minutes.

Step 6: Install the filter pump

Mount the Intex C1500 filter pump on a separate loop (or T into the chiller line). Run it 4–8 hours per day on the same timer as your chiller. Replace the paper cartridge monthly.

Step 7: Install the ozone generator

Plumb the Coospider ozone generator into the return line (after the chiller, before the water returns to the tank). The venturi injector sucks ozone gas into the water flow. Run 30 minutes, 3× per week. See our ozone installation guide for detailed plumbing diagrams.

Step 8: Fill and test

Fill with tap water. Run the chiller and filter for 24 hours to verify everything works and there are no leaks. Test water with 5-way test strips and adjust pH to 7.2–7.8. Add a small chlorine residual (1–2 ppm) as backup. Add the floating thermometer and verify it matches your Inkbird reading.

Step 9: Add safety features

• Plug all electrical components into a GFCI-protected outlet (mandatory)
• Route all power cords above the waterline (no dips where water can pool)
• Add a non-slip mat around the tank
• Keep a phone within reach
• Mount a small first-aid kit nearby

Step 10: First plunge

Once water reaches target temp (typically 45°F for beginners), do your first session. Have a buddy present. Limit to 1–2 minutes. Read our breathwork guide first.