DIY Cold Plunge: How to Build One and What It Costs

The easiest DIY cold plunge is a stock tank of about 100 gallons, filled with cold water and ice. When buying ice gets old, add a plug-in chiller with a filter. We sell cold plunge tubs and chillers, so we'll also say when you don't need one.

DIY cold plunge options compared

The big difference between builds is how you keep the water cold: ice you buy, or a chiller you plug in.

How much does ice cost?

The tub is the cheap part. Ice is the cost that sneaks up on you.

By our math, cooling 100 gallons from 70 °F to 40 °F takes about 175 pounds of ice. That ignores heat from the air and your body. It assumes 8.34 pounds per gallon and about 144 British thermal units (BTU) of heat absorbed per pound of melting ice.

Here's an example. If a 20-pound bag costs $3 where you live, about 9 bags (175 pounds) is about $27 per full cool-down.

What you need: build or buy each part

Every cold plunge has the same five parts. Build the cheap ones and buy the rest. Retail prices below were listed at Tractor Supply and Home Depot in October 2026; prices change.

• Tub, build: A stock tank, chest freezer or bathtub. A 100-gallon poly stock tank was listed at about $120.
• Tub, buy: The Dynamic Inflatable Plunge, $899 and 38 pounds dry, with a chiller sold on its own.
• Cooling. Build: bags of ice, as in the math above. Buy: a plug-in chiller that cools to 37 °F.
• Filter. Build: a spa cartridge filter on a small pump. Buy: a chiller with a pump, filter and ozone (a gas that sanitizes water) built in. A spare Coldture Large 20-Micron Filter is $36.
• Cover, build: Foam board and a lid you cut to fit. Owens Corning FOAMULAR 150 1-inch rigid foam board was about $27 a sheet.
• Cover, buy: A tub that comes with a cover, like the Dynamic Inflatable.
• Power, build: Have an electrician add a GFCI outlet. Listed 20-amp GFCI models ran about $28 to $34 for the part. Check your chiller's nameplate for what it needs.
• Power, buy: A chiller with GFCI protection built into the unit or its cord.

We found no sourced price for a pump with cartridge filter, a DIY lid, a chest freezer or an electrician's labor, so get local quotes.

How to build a stock tank cold plunge

Set up the tank

1. Pick the spot. Choose level ground with drainage, some shade, and a grounded GFCI outlet within reach of the cord.
2. Build a level base. Use pavers, compacted gravel or a concrete pad to keep stress off the tank walls.
3. Insulate underneath. Lay foam board under the tank now, since you can't move it once it's full.
4. Choose your plumbing. Hoses over the rim need no drilling. Bulkheads, which are fittings that pass through the tank wall, look tidier but need a hole saw and a good seal. If you drill, add a drain valve at the bottom.

Fill it and cool it with ice

1. Fill and leak-test. Fill the tank, dry every fitting, and watch for drips.
2. Add ice. Add it right before you get in, since it starts melting at once.
3. Cover it. A lid keeps out sun and leaves between sessions. Keep it covered and latched if kids or pets are around.

If you're using a chiller

1. Measure the rim. The Coldture adapter clamps onto walls 2 to 6.5 inches thick.
2. Clamp on the adapter. It comes with two return pipe sizes, so pick the one that fits your tank's depth.
3. Connect the lines. Run the supply and return lines from the adapter to the chiller.
4. Power on and check flow. With the tank full, plug into a grounded GFCI outlet, switch on, and make sure water flows back into the tank.

Do insulation and a cover help?

Yes. Insulation under and around the tank usually slows how fast the water picks up heat, so ice lasts longer and a chiller runs less.

Don't skip the cover. The Dynamic Inflatable's has child-safe locking clips.

Adding a chiller: size and setup

A chiller is a small refrigeration unit. It pulls water from the tub, cools it, and sends it back. Most also filter and sanitize the water.

What size chiller do you need?

Chillers are rated in HP (horsepower), the size of the cooling unit. Size depends on tub volume, insulation and climate.

Both Dynamic models list up to 135 gallons. Dynamic says the Premier 1.0 HP cools 1 to 3 °F every 20 minutes. The 0.8 HP takes 30.

The Chiller Pro has no published gallon limit. Before you pair it with a 100-gallon stock tank, email your tank size to help@myfitnessoutlet.com so we can confirm the fit.

The Chiller Pro lists operating air from 14 °F to 120 °F. In a hot climate, shade and insulation give any chiller less work.

Expect the first chill-down to take hours. Dynamic lists its Standard chiller at 1 to 3 °F about every 30 minutes, depending on air temperature and water volume.

By our math, that's roughly 2 to 5 hours per 10 °F. For the same 70 to 40 °F drop as the ice math, expect roughly 5 to 15 hours, so start the day before.

Which chiller works with a stock tank?

For a stock tank, we suggest the Coldture Water Chiller Pro with the Coldture bathtub adapter. The adapter's listing names stock tanks and DIY plunges as compatible. If your rim falls outside the 2 to 6.5 inch range, email us before you buy.

Dynamic says its chillers are designed to work with Dynamic Cold Therapy tubs. So we pair them with Dynamic tubs, not stock tanks.

Coldture Water Chiller Pro

Our pick for a stock tank or other DIY tub, once you've confirmed the fit with us. It draws 850 W on average.

Can you build your own chiller loop?

Some builders do. Water runs from the tub outlet to a filter, a pump and the cooling unit, then back through a return line. We can't advise on self-built loops. If you try one, open the filter's bleed screw until water, not air, comes out, since trapped air can keep the pump from priming.

You also wire it next to water and chase every leak yourself. Most people buy a plug-in unit with the pump, filter and ozone in one box.

Read the warranty before you hook it up

A chiller warranty assumes you follow the manual.

• Coldture doesn't cover damage from "chemical abuse or poor water chemistry," neglected filter care, low water flow or restricted air flow. It also excludes "unauthorized electrical modification."
• Dynamic Cold Therapy doesn't cover damage from poor water chemistry or "failing to regularly change out water," or use at or below 32 °F. Labor isn't covered.

So use a tub the maker lists as compatible, never rewire the chiller, and keep the water clean. See Coldture's warranty page for full terms.

Chest freezer cold plunge: read this first

A chest freezer is already insulated and has its own compressor. But it's built to cool food, not to hold 100 gallons of water with a person in it.

A 15-cubic-foot freezer holds at most about 112 gallons (15 × 7.48 gallons per cubic foot), and less once you count the walls.

Here are our cautions:

• It isn't made to hold water. Seams can leak, and bare metal can rust.
• The lid can trap you. A closed lid is hard to open from inside. Remove it or prop it so it can't close on you.
• The wiring sits inches from the water. A leak or a splash near the compressor is a shock risk.

Can you turn a bathtub into a cold plunge?

Yes. The cheap way is cold tap water and ice, but you'll need fresh ice every session.

For no ice, use an adapter and a chiller. The Coldture Bathtub Cold Plunge Adapter is $449 and weighs 3.3 pounds. Clamped onto tub walls 2 to 6.5 inches thick, it connects to the Chiller Pro with 0.5-inch lines.

Together they cost $3,948. We suggest the pair for renters and small spaces: nothing to drill, nothing big to store.

Coldture Bathtub Cold Plunge Adapter

Best for renters and apartments: paired with the Chiller Pro, it turns the tub you have into a cold plunge.

No bathtub? The Coldture Classic + Chiller Pro pairs an inflatable tub with the same chiller for $3,499.

Power and electrical safety

A GFCI (ground-fault circuit interrupter) is a fast-acting breaker. OSHA says it cuts power within as little as 1/40 of a second when current leaks to ground.

• Use a grounded GFCI outlet. Dynamic chillers list a built-in GFCI and Coldture's has a GFCI cord, but Coldture still asks for a grounded socket. Outdoors or around pools, spas and hot tubs, the CPSC says to plug in only to working GFCI outlets.
• Test it monthly. Press TEST and the power should cut off. Press RESET and it should come back. If not, replace it.
• Skip extension cords. The CPSC notes they aren't as safe as permanent house wiring. If the cord won't reach, add an outlet.
• Keep gear dry. The CPSC warns that wet products can leak current, even plastic ones. If something falls in, unplug it before you reach for it.
• Check the nameplate. Match the outlet to the label on the unit. The Chiller Pro lists 110-120 V and 850 W average. The Pro Plunge (NEMA 5-15, 850 W) and Dynamic chillers plug into a standard 120 V outlet. If your outlet doesn't match the label, ask an electrician.
• Hire it out. A new circuit is a job for a licensed electrician.

How to keep the water clean

• Filter. Rinse the cartridge on the maker's schedule and replace it when worn.
• Ozone. The Chiller Pro cycles the water every 15 minutes through a skimmer, a filter and ozone.
• Sanitizer. There's no cold plunge standard. As a hot tub benchmark, the CDC calls for at least 3 ppm (parts per million) free chlorine and advises against stabilized chlorine (cyanuric acid) in hot tubs. Its public hot tub guidance lists 4 ppm for bromine. For a cold plunge, follow the label on the pack.

The Coldture Premium Chemical Starter Pack ($100) has stabilized chlorine granules, an alkalinity product, an oxidizer and test strips. Add them to the water, never to the skimmer or pump basket. It's with spare filters in our cold plunge accessories.

How often should you change the water?

There's no cold plunge standard for this either:

• Ice, no filter: change it often. Every few days is our rough estimate, not a published rule.
• Chiller with filter and ozone: the Coldture Chiller Pro listing says it keeps water clean for up to 30 days of daily use.
• Any chiller: Dynamic's warranty doesn't cover failing to change the water regularly, so follow the manual.

Change it sooner if the water looks cloudy or smells off.

Where should you put a cold plunge?

A 100-gallon tank holds about 834 pounds of water before you get in. Indoors, make sure the floor can carry that.

• Drainage. Water splashes out each time you get in, so pick a spot where it can run off.
• Airflow and shade. Leave open space around the chiller's vents, since Coldture's warranty excludes restricted air flow. Give it shade too.
• Winter. Per Coldture, its tubs and chillers work outside down to 14 °F, with a low heat mode that keeps water from freezing. Dynamic's warranty doesn't cover chiller use at or below 32 °F.

Build or buy: when a ready-made plunge makes sense

Once you add a chiller, the price gap between building and buying gets small.

The Classic bundle costs the same as the Chiller Pro alone, tub included. A stock-tank owner may be better off with it.

The Pro Plunge holds 110 gallons and has a 1 HP chiller, filtering and ozone built in. The downsides are price and size: it's 76.75 inches long and 1,187 pounds full.

Coldture Pro Plunge

Cold plunge tub: 110 gal, cools to 37°F (heats to 104°F), 1 HP chiller

For anyone who wants to skip the build: everything in one unit on a standard 120 V NEMA 5-15 plug.

How cold and how long should your first plunge be?

Mayo's news network says water 50 °F or colder, and people typically start with 30 seconds to a minute. Harvard Health notes there's no agreement on the best temperature, timing or length. Our guide on how long to stay in covers it in detail.

Cold water triggers a gasp and fast breathing at first, so get in slowly.

The bottom line

Start your DIY cold plunge with a stock tank and ice, and add a plug-in chiller on a grounded GFCI outlet if you plunge daily.

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