Tdi 300 Water seperater located near the fuel tank.

I have a DEFENDER C130 1995 Tdi300 owned for about 15 years. I have only ever drained the water seperator via the nylon fitting but never performed any other maintainance on it. There are two canisters, i expect the top one is to collect the rubbish from the tank.
I see there is a bolt on the top of the housing that is unscrewed to release these two canisters.
I would appreciate being advised what will i find when the two canisters are remove. I expect it will require cleaning, there may be a filter to be replace and new O rings to be purchased.
I replace the engine bay fuel filter every 12 months and it is drained every 26 weeks.
I want to have the parts on hand so i do not get stuck.
Thank you in advance.

Hello and welcome to the forum

Thank you.
After posting, I realised my post was in the incorrect location.
Time has moved on for the real, 'Landrover Defender'. At some stage, they will be gone like their driver. But never forgotten.

It’s called a sedimenter with two O rings, unbolt from the top and drop both the cylinders,
No filter it’s just a sediment and moisture trap, give it a clean and refit with new O rings,

Welcome to the forum