Short answer: the Pure Water Treatment Kit contains a 16 fl oz sanitizer, a 32 fl oz oxidizer, and 25 test strips, for $75. The doses are small, so the bottles last a long time. The test strips will run out first.
Run the numbers
Renu’s published dosing is:
- At each water change: 2 tsp of sanitizer and 2 tsp of oxidizer
- Weekly: 1 tsp of oxidizer
- Sanitizer: more as needed, based on the test strips
There are 6 teaspoons in a fluid ounce. So the oxidizer bottle holds 192 tsp and the sanitizer bottle holds 96 tsp.
At 1 tsp a week plus 2 tsp at each water change, a year of oxidizer is under 70 tsp. The bottle covers more than 2 years at that rate. The 25 strips, used weekly, last about 6 months. So the first thing you’ll reorder is test strips, at $15 a pack.
Check the expiry dates on the bottles. A product that would last 2 years by volume may not keep that long once opened.
What does each part do?
- Sanitizer: controls bacteria and algae in the water.
- Oxidizer: breaks down the sweat, oils, and lotions that people bring in.
- Test strips: show sanitizer level, pH, alkalinity, and calcium hardness.
You need all three. Sanitizer without oxidizer can leave the water cloudy. Either without testing is guesswork.
Will it suit your tub?
The dosing is sized for a home cold plunge, not a pool. Renu’s Cold Stoic holds about 95 gallons. If your tub is much larger or smaller, ask Renu how to scale the dose. The listing says the kit is not marketed for tubs with certain metal or specialty finishes. If your tub has an aluminum or copper interior, check with its maker first.
How do you use it safely?
Measure with a dedicated spoon. Add each product to the water separately. Never mix the two liquids together, and store them out of reach of children. Run the pump after dosing so the water mixes before you get in.
How it compares
The Renu Sanitizing Spa Stick is a drop-in mineral option at $27.99 for about 3 months. Cold Plunge Sanitizer: Mineral Stick or Full Kit? compares the two. Our button goes to Renu Therapy’s product page.
