Have hidden cistern for a Space toilet and has worked fine. Changed to Fluidmaster inlet valve and still worked fine although pressure v. low (less than 1m. head). As cistern filling some water trickles through the internal overflow and did sometimes even after cistern filled. Assumed this was down to hard water deposits stopping the flush valve (if that's what it's called) seating properly so gave it a good clean out with limescale remover but now water going through internal overflow when filling is as much as water coming in through inlet valve SO CISTERN WON'T FILL. Can fill by using shower pump on system so can use loo but want to solve problem. Happy to replace either valve, if that's what it takes although Space cistern doesn't seem amenable to replacing flush valve with B&Q/Screwfix etc. replacement. Anyone help?
PS tried things like checking washer (a la Project Page) but seems different. Also e mailed Space but no reply.