How often should I drain my cold plunge?

With ozone + filter + low chlorine, every 4-6 months (2-3 times per year). Without ozone, every 2-4 weeks. Without ozone AND without a filter, weekly. Signs it's time: TDS above 1500 ppm, water won't clear, persistent smell, or it's been 6 months since last drain.

How do I drain my cold plunge?

Turn off all equipment, attach a garden hose to the drain fitting, run the hose to a safe drain location (sanitary sewer cleanout or lawn - never storm drains), open the drain valve and let gravity drain (20-30 min for 50 gallons), clean the interior with 10% bleach, refill with tap water, re-balance chemistry.

Can I drain cold plunge water into my lawn?

Yes, if chlorine levels are low (under 1 ppm) and you let the water sit 24 hours for chlorine to dissipate first. Don't pour chlorinated water directly on edible garden plants. For water with higher chlorine, neutralize with sodium thiosulfate (pool supply store) before draining. Never drain into storm sewers - chlorine harms aquatic life.

How do I clean the inside of my cold plunge?

Spray with 10% bleach solution, let sit 10 minutes, scrub with microfiber cloth or soft brush (never abrasive scrubbers), rinse thoroughly. For stubborn stains, sprinkle baking soda and scrub with a damp cloth. Re-seal any compromised bulkhead fittings with food-safe silicone before refilling.

How to Drain & Refill Your Cold Plunge (7-Step Process)

When to drain

Even with perfect water care, you'll need to drain and refill your cold plunge every 4–6 months. Signs it's time:

Total dissolved solids (TDS) above 1500 ppm (test with a $10 TDS meter)
Water won't clear even after filtration and shocking
Persistent smell that doesn't resolve after ozone treatment
Cloudiness that doesn't resolve after 24 hours of filtration
It's been 4–6 months since last drain (the practical maximum)

What you'll need

Garden hose (long enough to reach a safe drain location)
10% bleach solution in a spray bottle
Clean microfiber cloth or sponge
Baking soda (for stubborn stains)
Food-safe silicone (for re-sealing any fittings you remove)
Replacement filter cartridge (if due)

The 7-step drain process

Step 1: Turn off all equipment

Power down chiller, filter pump, and ozone generator. Unplug from the wall. This is critical — running a chiller dry will burn out the compressor in minutes.

Step 2: Attach drain hose

Most stock tanks and plunge tubs have a threaded drain plug near the bottom. Remove the plug and thread in a garden hose adapter (available at any hardware store for $5). Run the hose to a safe drain location. Never drain chlorinated water into storm drains — it harms aquatic life. Drain to a sanitary sewer cleanout, a lawn (chlorine dissipates in 24 hours), or a gravel area.

Step 3: Drain the water

Open the drain valve and let gravity do its work. A 50-gallon tub takes 20–30 minutes to fully drain through a standard garden hose. While it drains, this is a good time to inspect the tub interior for cracks, stains, or biofilm buildup.

Step 4: Clean the tub interior

Once empty, spray the interior with a 10% bleach solution. Let sit for 10 minutes. Scrub with a microfiber cloth or soft brush — never use abrasive scrubbers, which scratch the plastic and create habitats for bacteria. For stubborn stains, sprinkle baking soda and scrub with a damp cloth. Rinse thoroughly with fresh water.

Step 5: Inspect and service equipment

With the tub empty, this is the perfect time to:

Check all bulkhead fittings for leaks or cracking
Re-seal any compromised fittings with food-safe silicone
Vacuum the chiller's condenser coils (improves efficiency)
Replace the filter cartridge if due
Clean the ozone generator's injector nozzle
Inspect the chiller's water pump for debris

Step 6: Refill with fresh water

Close the drain valve. Fill with tap water using a garden hose. Fill to about 4" below the rim — overfilling causes overflow when you enter. Add a hose-end carbon filter ($15) if your tap water has high chlorine — this prevents chemical smell and reduces eye irritation.

Step 7: Re-balance water chemistry

Once filled, run the chiller and filter for 1 hour to mix the water. Test with 5-way test strips:

pH: adjust to 7.2–7.8 with pH Up or pH Down
Total alkalinity: adjust to 80–120 ppm with baking soda
Chlorine: add to 1–2 ppm with trichlor tablet
Hardness: if too soft, add calcium hardness increaser

Run the ozone generator for 30 minutes to sanitize the fresh water. Your plunge is now ready for use.

Disposing of old water responsibly

Cold plunge water contains chlorine, ozone breakdown products, skin cells, and possibly pathogens. Responsible disposal options:

Option	Best for	Notes
Sanitary sewer cleanout	Best option	Municipal water treatment handles chlorine and organics
Lawn or garden	Low-chlorine water	Let chlorine dissipate 24 hrs first; don't pour on edible plants
Gravel/drainage area	Outdoor plunges	Filters naturally through soil; avoid near waterways
Storm drain	NEVER	Chlorine kills aquatic life; illegal in most jurisdictions

⚠️ Local regulations

Many municipalities have specific regulations on draining pool/spa water. Check your local water utility's website before draining. Some require you to neutralize chlorine first (add sodium thiosulfate, available at pool supply stores) and may limit drain volume per day.

Quick reference: drain cycle math

How long your water lasts depends on your setup:

Setup	Water lifetime	Annual drain cycles
No ozone, no filter	1–2 weeks	26–52
Filter only	2–4 weeks	13–26
Ozone + filter	3–6 months	2–4
Ozone + filter + low chlorine	4–6 months	2–3

The combination of ozone + filter + low chlorine is the gold standard — most DIYers with this setup drain just 2–3 times per year.

📚 Related

For the full water care protocol, see our water care guide. For weekly maintenance, see our clean water routine.