JK wrote:
New house has an under-sink water filter system. The tap is a rather
nice one made by Franke and the filtration system is called Triflow. I
feel I should replace the cartridge as I have no idea how old the old
one is. Anyone know a good/cheap supplier online?

I have bought replacement Triflow cartridges from

http://www.water-systems.co.uk/

They certainly seem to filter out the iron particles in my water supply
as effectively as the original one.

I replace ours when the flow slows down noticably which is precumably
when the filter is clogged up.

Neil