Unable to attain a cistern syphon watertight seal
Hi, I am in the process of replacing a syphon in a toilet cistern. I have removed the cistern and syphon without a problem. However upon cleaning the cistern around the syphon outlet hole I have noticed a lump of porcelain on the upper side of the hole at the edge. This is porcelain and not lime scale, it is 2-3mm high and about 10mm wide with rough edges. This is preventing me from getting a water tight seal when installing the new syphon unit. I have tried without any success to remove the lump. Any ideas?
Is it possible to remove the lump of porcelain without breaking the cistern or do I try and pack all around the outlet hole with sealant, if so what type of sealant.