Water Filter Replacement – How Often?

How often should I change my water filter?


If you have a carbon Filter (the majority of water filters have a carbon filter), here is my advice on how often to change the filter.  For a reverse osmosis (RO) unit changing the filter is a little different, but you still need to change filters regularly – see below.

How often should I change my carbon water filter?

There are four ways you will know it’s time to replace your water filter.

Time or Taste or Look or Flow

Time:  In general, replace your filter every six months.  This is for normal usage (although I never know what the definition of “normal” is!).  Replace the filter more often if you drink a lot of water.

Taste: if your water starts to taste or smell funny, it’s time to change the filter.

Look: if the water is discoloured, or if you see things floating in it, it’s time to change the filter.

Flow: if your flow of hot water through the filter gets slower and slower, it could mean your filter is clogged and it’s time to change it.

How will I remember to change the filter?

Filters with Indicators: this is the easiest method.  Some water filters, especially those attached directly to faucets, have indicator strips which change colour when it’s time to change the filter. These indicators may not correspond with the number of calendar months suggested by the manufacturer, but they are usually quite accurate.   (Be aware though, that some water filter systems are affected by hot water flowing through the faucet; so be careful when making the switch from passive to active filtering mode).

Sign up for an e-mail reminder: many of the better-known companies such as Brita offer a reminder service, or use this reminder service for any other brand.

Bonus tip – you can also use this general reminder service to get an e-mail whenever you need to change your air-conditioning or furnace filter!

Mark it on your calendar:  If a water filter is rated to last 6 months, for example, then make a note on your calendar six months from the date you installed the new cartridge.  You could also mark the date of installation somewhere near the filter unit itself together with the replacement date.

Do I HAVE to replace my filter at the recommended time?

No.  Some water filters perform well even months after their recommended change.  Others may not last nearly as long.   It depends on:

  • How much water you use
  • What’s in your water that needs to be filtered out
  • The quality of your filter

Since replacement filters can be expensive, you may want to wait until the filter has definitely reached its maximum capacity.

You can have a look at the filter to see how ‘dirty’ it is.  You can wash off particles from the surface of the filter to extend its life.  You can even back-flush it (normally only once) which will make it last longer.  Eventually of course it will become full of gunk and you’ll have to replace it.

Do you have any tips for changing the filter?

Of course!

  • Save the packaging from the last filter – it will have instructions on it, plus you can use the packaging for when you recycle it.
  • Have the new filter ready to go when you open the compartment containing the old filter.
  • Have a waterproof container (e.g. plastic bag, trashcan) ready to receive the old filter.
  • Either use gloves or wash your hands very well after changing the filter.
  • After you’ve changed the filter, let some water to run through the filter in order to eliminate left-over contaminants and to prime the new filter.  Don’t drink the water which first comes out of the tap after replacing the filter. After a few minutes, the water should be perfectly safe to drink.
  • And of course, don’t let that first water go down the drain – use it to water the plants or for cleaning!

How often should I change the filter on a reverse osmosis unit?

There are more components in an RO system, and they need to be changed at different times.

Most Reverse Osmosis Filter Systems say that:

  1. Pre and post filters should be changed every 6 to 12 months.
  2. The membrane should be changed every 2-3 years OR if you notice a significant drop in water passing through the reverse osmosis system.
  3. The O-rings should be changed every other filter change on the pre and post filters and every change on the membrane.

See the tips above for carbon filters – most of them apply to RO units too!


Other interesting articles on water filters:

Choose the best water filter for YOU!

Which type of water filter is best?

The best water filter for Las Vegas and for Barcelona

Is your drinking water safe and tasty?

Is chlorine in water good or bad?

Bottled versus tap water – the taste test (video)


Comments on this entry are closed.

  • Bud Oct 2, 2013, 7:30 pm

    How do you change Ecco Water Osmosis filters? I have 3 in my system.

  • Stephanie Aug 25, 2012, 10:51 pm

    We changed our GE fridge water filter but the water came put hot after a couple of minutes. When we put the old one back in the water is not hot. We tried a third new filter and got hot water again. What to do? All three filters came together in a package

    • Clare Delaney Aug 26, 2012, 4:55 pm

      Hi Stephanie, I know all about eco friendly, but warm water from a fridge – no, I’m really sorry I can’t help you there. That seems so weird, that a fridge water filter can have that effect. I think I’d take them back to where you bought them from. Sorry I can’t help more – I would if I could!

  • Will Oct 3, 2011, 8:25 pm

    Have read with interest all the last weeks comments on Clare’s blogs about filters. If a representation of the US it would appear that vast numbers of people in the US ONLY drink at least filtered water. And then don’t change the filter…………… In conclusion, I typically drink tap water, unfiltered for over 50 years wherever I have lived, make the occasional foray in to bottled due to travel, but still alive and kicking.

  • Neil Dhawan Oct 3, 2011, 4:13 am

    Another Brilliant and Helpful article, Clare ~

    It’s easy to see why you are in demand to give lectures about going green. Now you may have already written an article on the subject, but if you could explain a bit about this “back-flushing” – what is it and how do you do it?

    Stay Extraordinary and Do Great Things, Neil

  • Internet Dating Success Oct 3, 2011, 3:02 am

    Hi Green Goddess,

    Thank you for mentioning the timing of water filter replacement in you complete coverage of the topic of drinking water and water purification.

    Happy Dating and Relationships,

    April Braswell

  • The Knowledge Stylist Oct 3, 2011, 1:57 am

    This is something that I myself sometimes struggle with. Even though I see the reminder I’m like “ugh, do I really need to change the filter!.” Great info as always.


  • Rob Malone Oct 3, 2011, 1:07 am

    Thanks Clare – one thing we are definitely not diligent enough with at our house is changing the filters.

  • Eva Palmer Oct 2, 2011, 11:48 pm

    I never remmeber when I am supposed to change my filters!
    I should just do what you say about writting it down on the calendar! So easy.,…

  • Kevin Bettencourt Oct 2, 2011, 8:54 pm

    For my water filter replacement I change the water filter cartridge in my refrigerator. I usually do it every six months or so.

  • John Moulder Oct 2, 2011, 4:55 pm

    I was wondering if you had to stick by the manufacturers suggestion , when changing filters , Thanks Clare .

  • Dennis Perry Oct 2, 2011, 1:17 pm


    This is a very helpful reminder. I have a filter within an espresso machine that is waaayyyy overdue. Got to get it changed TODAY!

    Thank you.

  • Body language Oct 2, 2011, 11:13 am

    My filter also is through the door of my freezer and I have to change it every 4-6 months but it is better than drinking non filtered water.
    Scott Sylvan Bell

  • Michael D Walker Oct 2, 2011, 11:12 am

    I remember changing out the filter on my refrigerator water line once and it was pretty disgusting by the time the change filter light came on. Glad it reminded me but after that I switched to marking it on my calendar.


  • Andrew Miner Oct 2, 2011, 10:49 am

    Sooo… what you’re saying is the the filter I’ve been using for 2 years now is bad? 🙂
    Very informative post on the different intervals and factors of changing your water filter. Carbon or Reverse Osmosis. Thanks!


  • Cherie Miranda Oct 2, 2011, 9:25 am

    I am using a Zero Water filtration system, which is pretty incredible for a pitcher type system. My biggest gripe, however, is that the filters don’t last long at all and are VERY expensive. I use the filtered water for cooking as well, so I do tend to go through quite a bit of it.

    I’m thinking of getting a second pitcher, a Brita, now that you’ve mentioned the recyclability of the filters. I might use that one just for cooking and the Zero Water pitcher for drinking. Or something like that. 🙂

    Thanks for the info!

    Cherie Miranda

    Holistic Health Expert

  • Lisa McLellan Oct 2, 2011, 7:55 am

    We only filter the water that comes through the freezer door, and thankfully there is a little light indicator that tells you when it is time to change the filter. We did have one on the faucet on the kitchen sink but it broke and we never replaced it. I can’t remember if it had an indicator or not. I remember the filter looking pretty nasty when we changed it though! Filters are important.

    Lisa McLellan