Question:
She who must be obeyed decreed that we had to have a drinking water filter tap by the main one - that was 8 months ago. Now the flow through the filter appears to me to be just as it was when first installed - and there are no complaints about the taste / smell / colour of the water - and presumeably given that the capacity of the element is finite it's life will greatly depend on volume of water and concentration of contaminates which must widely vary from any 'norm'

Anyone got any experience of the longevity of these filters?

Answer: Some of the filters include a metering capability that alerts you after a preset amount of water has been passed through it - that makes it pretty easy. If yours does not then I suppose you could try and monitor the water useage through it for a few days to work out an average usage per day. Then (if the manufacturer gives a quantity of water that each filter can handle) calculate a number of months it will take you to use that much.... I live in Scotland and do not use a filter and drink the water straight from the tap but when I visit my son in Newbury his water tastes terrible straight from the tap so I bought a filter jug and it does make a difference. I'm trying to persuade him to fit a filter for his water but he drinks bottled water(comes in brown bottles or cans) and since he lives alone he does not think the expense is justified.One issue is growth of bacteria in the cartridges, in the material they have filtered out. Commonly, silver in some form is used to limit this, and I believe that is the component which wears out, resulting in increased bacteria levels. Having said that, I always use my Brita cartidges for at least 3 months, 3 times longer than you're supposed to, and these have the same issue. The water softener and whatever removes the chlorine "swimming pool" smell from our tap water in them has never worn out on me, and I'm in a hard water area. My Brita filter is always kept in the fridge though, which may also help with limiting bacteria