The stated intervals
| Filter | Stated life | Where, and a note |
|---|---|---|
| K45-B shower cartridge | Up to 3 months | Product page: "Cartridge life is up to three months, depending on water quality and usage." |
| SK99-NEW stages 1, 2, 3 | 3-6, 6-12, 12-18 months | Product page replacement schedule (M3001, M3002, M3003). The M3005 set is listed as a 1-year pack. |
| MK99 FZ-2 | 3-6, 6-12 and 6-8 months | Three lines on the product page: the parts note, the parts list and the FAQ. |
| PD600-TAM3 ASR211, ASR212-600G | 12 and 24 months | The FAQ also gives hours of pump running: 60 hours (about 900-1000 gal) and 120 hours (about 1800-2000 gal). TAM3: about 900-1000 gal. |
| PX600 ASR711, ASR712-600G | 6 and 24 months | Parts list on the PX600 page. |
| MD40 dual filters | Up to 6 months or about 400 gal | Product page: depends on feed water and daily use. |
What the maker says about these numbers
- Lives come from lab tests on specified water; the real life depends on your water quality and daily use (FAQ).
- For the MK99 the FAQ says "there is no exact time to tell customers when to change the filter".
- For the RO systems the life indicator is based on pump running time: "if you didn't use the system much, the indicator will not change colors." The maker's advice: change on the suggested time.
- The MD40 page says homes with higher use or poorer source water may need to replace sooner, and to follow the indicator and watch taste and flow.
Worked example: first change windows
This is our arithmetic. Rule: the first change window for a stated range of a to b months runs from month a to month b; the second window, if you change on schedule and the clock restarts, runs from 2a to 2b. For a single figure, the window is that month. Install in month 0.
| Filter | Change 1 | Change 2 | Inputs |
|---|---|---|---|
| K45-B | by month 3 | by month 6 | up to 3 |
| SK99 stage 1 | months 3-6 | months 6-12 | 3-6 |
| SK99 stage 2 | months 6-12 | months 12-24 | 6-12 |
| SK99 stage 3 | months 12-18 | months 24-36 | 12-18 |
| MK99 FZ-2 (earliest figure) | months 3-6 | months 6-12 | 3-6 |
| PD600 ASR211 | month 12 | month 24 | 12 |
| PD600 ASR212-600G | month 24 | month 48 | 24 |
| PX600 ASR711 | month 6 | month 12 | 6 |
Count over 24 months, our arithmetic: a K45-B cartridge used to its 3-month maximum is changed 24 / 3 = 8 times, and more often if it clogs sooner. An SK99 stage 1 filter is changed between 24 / 6 = 4 and 24 / 3 = 8 times.
Gallon limits, our arithmetic. The MD40 states about 400 gallons or 6 months, whichever comes first. 6 months is about 182 days, and 400 / 182 is about 2.2 gallons a day. If you pour more than that, the gallon figure arrives before the month figure. The PD600-TAM3 ASR211 states 900 to 1000 gallons or one year. 900 / 365 is about 2.5 and 1000 / 365 is about 2.7 gallons a day.
Your worksheet
| Filter | Install date | Maker's stated life | Reminder date (short end) | Changed on |
|---|---|---|---|---|
What the pages do not say
- What happens to a filter's claimed performance if you run it past its stated life.
- A gallon figure for the K45-B shower cartridge. It states months only, so a shower you run a lot may shorten it.
- Why the MK99 page and its FAQ give different figures for the same FZ-2 filter.
- We left out prices on purpose. They move. Check the page for the current cost of each cartridge.
The cheaper or simpler option
A calendar reminder costs nothing. Set it at the short end of the range, then adjust when you see a change in flow or taste. For a shower, our showerhead guide covers flow, and a drop in flow is worth checking before you blame the cartridge. If the schedule looks like more upkeep than you want, a filter that needs no plumbing may fit better; see our pitcher guide.
If you want the schedule next to the system
Our reason to click: the PD600-TAM3 and SK99-NEW pages list each replacement cartridge with its stated life beside the system, so you can plan the changes before you buy.
We earn a small commission on qualifying sales, and 90% of it goes to charity (you can pick which); your price is unchanged. Full disclosure.
Sources
- Frizzlife K45-B, SK99-NEW, MK99, PD600-TAM3, PX600 and MD40 product pages, and the FAQ page, frizzlife.com, read 2026-11-01. Maker claims; the arithmetic is ours.