Quick answer
Replace a filter at the earliest of its manufacturer’s stated time limit, capacity limit or indicator alert. For current examples, BRITA states up to 150 litres or four weeks for MAXTRA PRO; Waterdrop currently gives the WD-10UA an up-to-12-month service limit. Neither example should be used as a schedule for a different model.
Why changing filters on time matters
I have 25 years working in industrial coatings filtration, including 18 years building and refining RO, carbon and resin systems. The common mistake is simple: a filter is easy to forget when it is out of sight. Once it reaches its stated service limit, it may no longer perform as intended.
Use the manual first, then the practical signs
- Time, capacity and indicator: use the earliest applicable manufacturer limit.
- Flow, taste or odour: a change is a useful prompt to check the filter and instructions; it does not prove a particular cause.
- Unusual water: if water looks or smells unusual, stop using the filter and follow the manufacturer’s hygiene or support advice.
Replacement schedules: start with your exact model
The table deliberately avoids fixed prices and made-up category averages. Those figures become stale quickly and can lead you to use a different product beyond its intended limit.
| Filter or system | Replacement guidance | What to follow |
|---|---|---|
| BRITA MAXTRA PRO cartridges | Up to 150 litres or four weeks, whichever comes first | This is BRITA UK’s current MAXTRA PRO guidance. Check the cartridge and jug instructions for the exact product you own. |
| Waterdrop WD-10UA | Up to 12 months | Waterdrop’s current UK product information gives a 12-month service limit. Capacity wording varies within the live product information, so follow the current manual or product page for your exact version. |
| Other jug and faucet filters | The exact model’s stated time or capacity limit | Do not transfer a replacement interval from another cartridge, brand or model. |
| Reverse-osmosis systems | The exact system manual and its replacement indicator | Pre-filters, post-filters and membranes have separate schedules which vary by system and feed water. |
| Whole-house and sediment filters | The housing/filter manufacturer’s stated limit | Sediment load and local water conditions can affect the practical service life. |
What can affect a schedule?
Water conditions
Hardness and sediment can affect practical service life, but there is no responsible universal percentage adjustment. Use the model’s limit and indicator rather than guessing from your postcode.
How you use it
More filtered water normally means reaching a capacity limit sooner. Note the installation date and follow any litres-used, app or indicator guidance for your own product.
Storage and hygiene
Check the pack and manual for storage guidance. Follow the manufacturer’s cleaning instructions, especially after a long period of non-use.
Temperature
Do not run hot water through a filter unless the exact product manual says it is suitable. Temperature limits are product-specific.
A special note for RO systems
Reverse-osmosis systems have several components with separate schedules. Treat the system manual as the authority: it explains which pre-filters, post-filters and membrane apply to your model and what its indicators mean. Do not use a generic RO calendar to override it.
A sensible RO maintenance record
- 1. Record the model and installation date.
- 2. Keep the manual or official product page with its service intervals.
- 3. Set reminders based on the system’s separate components.
- 4. Follow the support guidance if performance changes or an indicator appears.
Frequently asked questions
How often should I change my water filter jug cartridge?
Use the interval and capacity stated for the exact cartridge. BRITA currently states that MAXTRA PRO cartridges provide up to 150 litres or four weeks, whichever comes first. Other jug cartridges can differ, so check the packaging and manufacturer guidance rather than borrowing a schedule from another brand.
How often should I change an under-sink water filter?
There is no reliable universal interval. Follow the exact filter’s time limit, capacity limit and any service indicator. Waterdrop currently gives the WD-10UA an up-to-12-month service limit, but you should check the current product guidance for the version you own.
How long does a reverse-osmosis membrane last?
Follow the manual for your particular RO system. The pre-filters, post-filter and membrane may have different replacement schedules, and feed-water conditions can affect them. Do not rely on a generic membrane lifespan when the manufacturer gives a specific service interval or indicator.
What happens if I do not change my water filter?
A filter used beyond its stated limit may no longer perform as intended. Reduced flow, a return of taste or odour, or a service indicator can be useful prompts to check the instructions. If water looks or smells unusual, stop using the filter and follow the manufacturer’s hygiene and support guidance.
How do I know when my water filter needs changing?
The manufacturer’s time limit, capacity limit and service indicator take priority. A noticeable change in flow, taste or odour is also a reason to check the product. These signs do not diagnose the cause, so follow the manual and contact the manufacturer if you are unsure.
Do whole-house water filters need changing?
Yes, but the correct schedule depends on the filter housing, media, source water and manufacturer instructions. Check the exact filter’s stated service interval rather than relying on a generic whole-house schedule.
The bottom line
Write down the installation date, keep the correct manual, and follow the earliest time, capacity or indicator limit for the exact filter you own. If you are unsure which standard or filter type applies to your concern, use the guides below before you buy a replacement.
Related Reading
About Keith
25 years working in industrial coatings filtration, including 18 years building and refining RO, carbon and resin systems
On Filter Authority, Keith translates hands-on experience into plain-English guidance and evidence-led, certification-aware recommendations for UK homes. You won't find hype here — just clear options, honest trade-offs, and how to check claims for yourself.
Read full bio and methodologyMaintenance guidance is model-specific. This article was last reviewed in September 2026. Always use the current documentation supplied with your own filter or system.