Can you extend the recommended operational duration of a water filter? Part 1

Dear Chen Ko

I hope this email finds you well!

Thank you for your insights which helped me greatly in choosing a water filter previously. Doulton has served me well. 🚰

I write again for your advice on when to replace filters - the most troublesome part as it can be a bit of an art and science, especially where there is no replacement indicator on the filter.

1. The recommended period for replacement for my Fluoride pre-filter cartridge and ceramic candle was
   9  to 12 months. However, because of [a] what I view as low usage (about 6 litres a day), and [b] also the fact that the ceramic candle can be periodically cleaned (not that it is terribly yellow either), I had not followed this recommendation. 
• Are those two reasons "justifiable" for the delay in replacing my filters? 
• Are there any good, objective ways of gauging when exactly I should replace my filters? 
• What are the health dangers of delayed filter replacements? For one, you'd previously advised me about silver leaching even more from an old filter.
2. Based on the (considerably low) fluoridation levels in Singapore's water, is it possible to actually calculate a suitable replacement period for my Fluoride pre-filter cartridge? This is assuming that I may replace it at longer intervals compared to my ceramic candle, instead of replacing both at the same time. I'm presuming here that the ceramic candle will need to be replaced earlier - but do enlighten me if this is likely to be so.
3. Is it a good idea to store up replacement cartridges (be it Fluoride pre-filter or ceramic) for a year or two before use? Not sure if the material and elements will degenerate/degrade slowly.

I look forward to your thoughts on this topic. Oh yes - and a very Happy Lunar New Year to you!

Warmly, 

Paloma

Dear Paloma,

A very Happy Lunar New Year to you too! And good to hear that my recommendation has been useful to you. (For new readers to my blog, I do not derive any benefits from my recommendations unless explicitly stated otherwise.)

You have touched on a very relevant topic on water filters and yet there is so little useful information out there for the consumer. This is not without reason though.

Manufacturers of water filters make recommendations (say 3, 6, 9 or 12 months) of when you should change your water filter. 

1. Such recommendations are obviously based on certain assumptions e.g. number of people in a household, amount of drinking water consumed per person per day, tap water quality which may or may not apply to the consumer. Unfortunately, these assumptions are usually not communicated to the consumer.
2. There are filters out there with their operational lives given by the total volume of water filtered (say 1000 to 100000 gallons). Though still based on certain assumptions e.g. water quality, this is a lot more accurate than a time based measure. The obvious downside is the consumer will find measuring volume a lot more difficult (or expensive) than just keying a date in the calendar for replacement.
   
3. The operational duration is typically a conservative value to safeguard the claims made by the manufacturer who is confident that the filter can work effectively within given period.
4. Remember how printer suppliers earn their profits from you buying their printer cartridges? Same here. You are expected to change your filters regularly to provide  consistent profits to the water filter suppliers.

Besides time, are there other ways to know if your water filter is up for replacement?

1. Some purely ceramic filter elements (no activated carbon (AC) or other fanciful filtration media incorporated within) come with a ceramic gauge. The idea is a ceramic element can be scoured periodically to remove the residue on its surface. Scouring also removes some of the ceramic, gradually thinning the ceramic. The gauge serves to measure the thickness of the ceramic so once it goes beyond a certain limit, the element is no longer effective.
   
   Unfortunately, if your ceramic element does not come with a gauge, you are out of luck as there is no way to guess/calculate/estimate the thinness of the element before it is due for replacement.
   
   Or if your ceramic has AC or other media impregnated within, the AC or media will determine the life of the entire element as their effectiveness tend to run out MUCH faster than the ceramic itself. Incidentally, you did not mention which Doulton element you are using.
2. Total volume
   Already mentioned above but I just want to add that if you are really keen to keep track of the total volume of water filtered, you can install a flowmeter to automatically monitor this for you. Not cheap and not practical for a gravity filter, it is nevertheless an accurate way to tell you when to change filter.
   
   A cheap version of the above test is to work out your daily volumetric usage. Divide the capacity of the filter by your daily usage and you get your operational duration. This is provided the filter manufacturer has specified the capacity of the filter in total volume.
3. Blue dye test
   Certain filters incorporating AC allow you to test their effectiveness by running a blue dye solution (prepared by e.g. adding 2 drops of blue food dye into a cup of water) through your filter. If the filtered water has no visible blue colour, the AC is still working well. Otherwise, it is time to change filter. (Apparently, blue is commonly recommended as other coloured dyes do not work so well.)
4. Colour, odour, pressure drop
   Depending on a degradation in the colour and odour of your filtered water is somewhat like waiting to do something only when the problem arises. A reactive kind of attitude at best and dangerous at worst when contaminants from the raw water are already going into your drinking water.
   
   Another reactive solution is to wait for the filter to show an apparent drop in pressure i.e. your filtrate is not coming out as fast as before. Usually, this means the filter is clogged up with residue. Contaminants may or may not be going through the filter. Time to change filter or in the case of a ceramic element, time to scour its surface.
5. My solutionAs I don't use my Doulton filter regularly so I estimated the volume filtered in each trip and keep a record with the filter. Once it has reached the rated capacity (say 2000 litres), I changed it.Still, if the filter looks dirty or the flow is not smooth, I scour the filter surface. I keep a record of scouring too together with the usage. I believe Doulton specified a maximum number of scouring at 100 but treat this number with a pinch of salt as ultimately, it depends on how rough or gentle your scouring session is.

I believe this post has gone on longer than I wished. Thanks for your thought provoking questions. Let me answer the rest of your questions in another post.

Good luck!

Figure: A flowmeter that can total the volume of water passing through. Expensive but very useful to tally the amount of water going through your filter