Hi Simon, as mentioned by demifrog, I'd definitely not recommend using water on these fine filter cartridges either, as to the best of my knowledge they are mostly manufactured from paper. The advice to use high pressure water sounds very dubious to me!! It would turn into an expensive lump of paper mache. Tapping and compressed air is your best bet once in a while to keep them clean.
Cheers
Nick
Jet
Cheers
Nick
Jet