A water treatment system is only as good as its last service. Most of the failed systems we see were not bad equipment; they were good equipment nobody serviced. Here is what wears out, how fast, and how to know.
Sediment cartridges
The first stage catches the grit, so it clogs first. On municipal water a sediment cartridge may run six to twelve months. On a silty well or a lake intake it can need changing every few weeks in spring. A clear housing lets you see it. A pressure drop across the house is the other sign.
Carbon
Carbon adsorbs chlorine and taste compounds until it is full, then simply stops, with no warning. A cartridge on municipal supply typically runs six to twelve months. A backwashing carbon tank runs several years before the media is replaced. The tell is the chlorine taste coming back.
Reverse osmosis
Pre-filters yearly, or twice a year on harder or more chlorinated water, because they protect the membrane. The membrane itself lasts three to five years when the pre-filters are kept up. A TDS meter at the RO faucet tells you when the membrane is actually done, and we test it at every service rather than guessing.
UV lamps
Once a year, without exception. A UV lamp loses output long before it stops glowing, so a lamp that looks fine at eighteen months may not be delivering a safe dose. The quartz sleeve gets cleaned at the same time, because scale and iron film on it block the light. Our UV water purification page covers what a full UV service includes.
Iron filter media
Five to ten years depending on iron levels and how well the backwash keeps up. Staining creeping back is the sign. We check the media at each service.
Softener resin and salt
Resin lasts ten to fifteen years on clean water, less if iron has been getting through. Salt is monthly: keep the brine tank about half full and break up any salt bridge that forms. A yearly check of the settings, injector and brine system keeps a softener honest.
A simple service calendar
Most homes can group their maintenance into one or two visits a year rather than chasing each part separately:
- Monthly: check the softener salt level and look at any clear sediment housing.
- Once a year: UV lamp and sleeve, RO pre-filters, carbon cartridges on municipal water, and a check of softener settings and brine system.
- Every few years: the RO membrane when the TDS reading says so, and backwashing carbon or iron media when performance drops.
- As needed: sediment cartridges on wells and lake intakes, which follow the water rather than the calendar.
Writing the install date and next change date on each housing with a marker is the cheapest reminder system there is.
Why the box number is only a starting point
Every interval above depends on your water and your usage. A family of five on a silty well and a couple on Lake Ontario supply do not change cartridges on the same schedule. We set intervals from your test results and actual use, and our maintenance plan reminds you when each stage is due, on any brand, whoever installed it. On a well and not sure what your water is doing to your equipment? Start with in-depth well water testing. On town water with an RO system, see our reverse osmosis page.
Common questions
How do I know my RO membrane is done?
Measure it. A TDS meter reading at the RO faucet compared with the reading at an ordinary cold tap tells you how much the membrane is still rejecting. When the RO water reading creeps up toward the tap water reading, the membrane is worn. A change in taste is the other clue. Slow flow from the RO faucet, on the other hand, usually means clogged pre-filters or low tank pressure, not a failed membrane.
What happens if I do not change my water filter?
It depends on the stage. A clogged sediment cartridge drops pressure through the house. Spent carbon lets chlorine and taste back through without any warning. Overdue RO pre-filters let chlorine reach the membrane and shorten its life. A worn UV lamp can keep glowing while no longer disinfecting properly, which is the one that matters most on a well or lake supply.
How often should I change my UV lamp?
Once a year, whether or not it still lights. Clean the quartz sleeve at the same time. On a seasonal cottage, spring start-up is the natural time to do both. Our article on drinking Lake Simcoe water at the cottage covers the rest of a start-up.
How often should I add salt to my water softener?
Check it monthly and keep the brine tank about half full. Use salt made for softeners, and if the salt looks full but the water is getting hard again, push a broom handle down to break up any bridge that has formed over the water.
Can I change my own water filters?
Cartridge changes on a standard housing are a reasonable owner job if you shut off the water, relieve the pressure and lubricate the O-ring. UV lamps, RO membranes and media replacement are easier to get wrong, and a missed step on a UV system on a well is the one that matters. A maintenance visit also includes testing that a cartridge swap does not.
Why does my water taste odd after a filter change?
New carbon releases fine black dust and trapped air for the first few minutes. Run the water for several minutes after a change, and on an RO system empty the first full tank before drinking from it.