Most cold plunge upkeep is about clean water. The filter is different. It protects the chiller, the most expensive part of the tub.
This article covers when to change a filter and which one to buy. For the other accessories, see the cold plunge accessories buying guide.
Short answer: change the filter on the maker’s schedule, buy the maker’s own filter for your exact chiller, and keep spares on the shelf.
Why the filter matters to the chiller
A chiller moves water through itself all day. The filter catches what would otherwise go through the pump.
Plunge puts it plainly on its filter page: “Operating your plunge without a filter or with a dirty filter can shorten the life of the chiller and may void the warranty.”
Which filter fits
Filters aren’t universal, even within one brand.
| Filter | Fits | Doesn’t fit | Price |
|---|---|---|---|
| Plunge Filter Pack (All-In and Pro Chiller) | Plunge All-In, Pro chiller | Standard and 1st-generation chiller | $46 for 6 |
| Renu standard maintenance filters | Cold Stoic Classic, Cold Stoic 2.0, standard Siberian | Cold Stoic 3.0, Aurelius, Siberian Pro | $67 for 12 |
The Plunge filter is 30 micron and NSF-50 rated. Plunge also sells it in 12-packs and 24-packs.
How often to change it
Here’s what the spec sheet won’t tell you. Plunge’s product page doesn’t give an interval. It says regular replacement keeps performance up and links to a maintenance guide. Check your manual.
Renu Therapy does give one: its filters last 2 to 6 weeks in home use, depending on water quality and how much you use the tub. It says most customers change them every 2 to 3 weeks.
What a year costs
Run the numbers for your own pace.
| Change interval | Filters per year | Plunge (at $46 per 6) | Renu (at $67 per 12) |
|---|---|---|---|
| Every 2 weeks | 26 | About $199 | About $145 |
| Every 4 weeks | 13 | About $100 | About $73 |
| Every 6 weeks | 9 | About $69 | About $50 |
These are per-filter costs at the 6-pack and 12-pack prices. You’d buy whole packs, so round up.
Signs to change early
My rule of thumb: change the filter early if it looks dirty when you check it, or if the water has gone cloudy. A filter costs under $8. A chiller doesn’t.
Use the maker’s filters
You get a part rated for your chiller with the official filter. You give up the lower price of a generic one. Since Plunge ties filter care to the warranty, I wouldn’t take that risk to save a few dollars.
Chiller coverage varies by brand. The cold plunge buying guide covers warranties.
Bottom line: filters are the cheapest insurance on the tub. Buy the right ones and change them on time.
Sources
- Plunge, Filter Pack (All-in and Pro Chiller) product page (price, rating, compatibility, warranty statement), accessed October 8, 2026: plunge.com
- Renu Therapy, 12-Pack Maintenance Filters product page (price, compatibility, 2 to 6 week life), accessed October 8, 2026: renutherapy.com
- Renu Therapy FAQ (filter change frequency), accessed October 8, 2026: renutherapy.com