Replacement manifold seal The fibre washer forms the flat seal at compatible 1″ manifold ball-valve connections. It can be used to replace a missing, damaged or previously compressed washer when the joint is reassembled. Check the washer dimensions Confirm that the original washer measures 30mm x 23mm x 2mm and that the fitting is designed to seal against a fibre washer. Replace any washer that is split, distorted or otherwise damaged before tightening and testing the connection.