How often to change RO filters
A plain guide to the filters inside a home RO purifier, how long each one lasts and how to tell when it is due.
- Visit charge: told to you on the call, before we visit
- Warranty: 90 days on the work done
How often should I change the filters in my RO water purifier?
As a general guide, the sediment and carbon pre-filters are changed about every 6 to 12 months, the post-carbon filter about once a year, and the RO membrane every 2 to 3 years, sometimes longer with good water. Hard water, muddy water or heavy daily use shortens these times. Your purifier's manual and filter alert come first, and slow flow or a change in taste means a filter is due.
What each filter does
- Sediment filter: catches sand, rust and mud. It clogs first, especially with muddy or iron-rich water
- Carbon pre-filter: takes out chlorine and some odours that would damage the membrane
- RO membrane: removes most dissolved salts and many other impurities. It is the costliest part
- Post-carbon filter: polishes the taste of the stored water
- UV or UF stage, if your purifier has one: the UV lamp also has a rated life, given in the manual
Signs a filter is due
- Water comes out slower, or the tank takes longer to fill
- The water tastes or smells different
- A TDS meter shows a higher reading than it did after the last service
- The filter-change alert on the purifier comes on
- The purifier makes noise but gives little water, or stops
Why the pre-filters matter most
The sediment and carbon filters protect the membrane. When they are clogged or used up, dirt and chlorine reach the membrane and shorten its life. Changing the cheaper pre-filters on time is how you avoid buying a membrane early.
Do not wait for the water to taste bad before changing them.
When to call us
We change filters and membranes in home RO purifiers of most brands, and check the flow, the TDS and the pump while we are there. Price: Quote after diagnosis. See RO filter change.
Questions
Can I wash a sediment filter instead of changing it?
Most pre-filter cartridges are made to be replaced, not washed. Washing does not clear the fine pores inside, so the flow stays low.
Does a low TDS reading mean the water is safe?
No. A TDS meter measures dissolved salts, not germs. It is useful to watch how the membrane is doing, but the UV or UF stage and clean filters handle the rest.
Why does my new filter make the water taste odd?
A new carbon filter can give a slight taste until it is flushed. Let the first tank or two run to waste after a filter change.
Last updated 2026-11-08
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