Complete Replacement Schedule for Every Filter Type
I've seen it countless times in my 24 years in the industry: people invest in a quality water filter, then forget about it for years. An overused filter isn't just ineffective—it can actually make your water worse.
| Filter Type | Replace Every | Typical Cost |
|---|---|---|
Filter Jug Cartridges Brita, ZeroWater, Aqua Optima | Every 2-3 months | £5-15 per cartridge |
Tap-Mounted Filters Brita On Tap, PUR | Every 3-4 months | £15-25 per cartridge |
Under-Sink Carbon Filters Waterdrop, Doulton, Aquasana | Every 6-12 months | £30-60 per filter |
RO Pre-Filters (Sediment) All RO systems | Every 6-12 months | £10-20 per filter |
RO Pre-Filters (Carbon) All RO systems | Every 6-12 months | £15-30 per filter |
RO Membrane All RO systems | Every 2-3 years | £40-80 per membrane |
RO Post-Filter (Polishing) All RO systems | Every 12 months | £15-25 per filter |
Whole House Sediment Various brands | Every 3-6 months | £10-30 per filter |
Whole House Carbon Various brands | Every 6-12 months | £40-80 per filter |
Fridge Water Filters Samsung, LG, Bosch | Every 6 months | £25-50 per filter |
Don't wait for these signs—they mean your filter is already past its prime. But if you notice any of them, change your filter immediately:
Having worked with reverse osmosis systems for over 20 years, I can tell you the most common mistake people make: neglecting the pre-filters.
Your RO membrane is the most expensive component (£40-80), but it's protected by cheaper pre-filters. If you don't change those pre-filters regularly, chlorine and sediment will damage your membrane, forcing an early replacement.
Months: Change Pre-Filters
Sediment filter + carbon pre-filter
Months: Change Post-Filter
Polishing carbon filter (final stage)
Years: Change RO Membrane
Can last 5+ years with proper pre-filter maintenance
Most water filter jug cartridges (Brita, ZeroWater, Aqua Optima) should be changed every 2-3 months or after filtering approximately 100-150 litres. If you use your jug heavily (a family of 4+), you may need to change it more frequently. ZeroWater filters typically last 2-3 months but can vary based on your water's TDS level.
Under-sink carbon filters typically need changing every 6-12 months, depending on usage and water quality. Most manufacturers recommend 6 months for heavy use or 12 months for average use. Always check your specific filter's documentation, as some high-capacity filters can last up to 18 months.
RO membranes typically last 2-3 years with proper maintenance. However, the pre-filters (sediment and carbon) in an RO system need changing every 6-12 months. If you don't change the pre-filters regularly, the membrane will wear out faster. Some high-quality membranes can last up to 5 years.
An overused filter becomes less effective at removing contaminants and may actually release trapped contaminants back into your water. It can also become a breeding ground for bacteria. You may notice reduced water flow, bad taste, or odours. In worst cases, an old filter can make your water quality worse than unfiltered tap water.
Warning signs include: reduced water flow or pressure, return of chlorine taste or smell, visible discolouration of water, filter indicator light (if equipped), and reaching the manufacturer's recommended time or volume limit. Don't wait for all signs—if you've reached the time limit, change it even if water seems fine.
Yes, whole house filters need regular maintenance. Sediment pre-filters typically need changing every 3-6 months. Carbon filters every 6-12 months. The frequency depends on your water quality and household usage. Homes with well water or high sediment may need more frequent changes.
Your water filter is only as good as its last replacement. Set a reminder, keep spare filters on hand, and don't push it past the recommended schedule. The cost of a new filter is nothing compared to the health benefits of properly filtered water.
My rule of thumb: When in doubt, change it out. A slightly early replacement is better than drinking water through an exhausted filter.
Find Your Next Filter →Water Filtration Specialist | 24+ Years Experience
Keith has installed and maintained thousands of water filtration systems across the UK, from simple filter jugs to complex whole-house RO systems.
Read full bioReplacement schedules are general guidelines. Always refer to your specific filter's documentation for manufacturer recommendations. Information accurate as of January 2026.