Check your handbook to see if it has one ? It may have an IN LINE filter which some times is neath the sink,The common one which is mostly found will be where you plug your water pump into.I use what is known as a shifting key on mine while others may use pliers to turn it,It screws out ANTI clock wise and can be very stiff butat starting to screw off.
When you go to fit a new one put some cooking oil round the rubber seal.tighten but dont over do it.
I found these prone to frost damage even with system drained. Twice we had one crack over the winter. Since we don't drink the water from the aquaroll I replaced it with a piece of copper pipe. No more cracking.
------------- 74,going on 25
Beauty is in the eye of the beerholder
I removed mine and put a length of pipe in the same length as the filter so I can put one in if I decide later . I have kept the quick release couplings so no need to cut/ change pipes etc
Had one crack in an earlier van so we don't bother with one now and we drink from the aquaroll and have done so for years with no problem. Its cleaned along with pipes before every use while we set up.
Amazing family weekend with old steam engines, classic car displays, market stalls, and full catering and bar. And camping on site - Save £25 by booking in advance.