The toilet is hissing and the cistern isn’t filling up with water properly. We have pneumatic flush valve. Have tried fixing over the last couple of days but not having luck It’s a concealed cistern in a toilet/sink combination unit, with the cistern behind a panel above the pan. It has a pneumatic dual-flush valve, a side-entry fill valve and a blue isolation lever. What happened: the toilet had a weak flush and left tissue behind. We took the button out to get to the cistern, and since then: • the fill valve hisses constantly, even with the float arm held up, until the blue isolation lever is closed • the cistern sometimes won’t fill • water was trickling into the bowl after a flush, though that seems to have stopped What we’ve checked: the flush valve seal and seat look fine, the float had come apart and we snapped it back together, and we’ve taken the fill valve apart, applied limescale and put it back. Nothing looks worn or broken to us The cistern is already open, so access is easy. We have party starting from 7pm we need a working toilet for