Pressure discs are designed to rupture if the jetter pressure rises to unsafe levels. This could occur when a jetting nozzle becomes blocked or hoses are crushed. After rupture, the failed disc harmlessly allows the pump pressure to release, protecting the operator and equipment.
Sometimes called burst discs or rupture discs, they are single use and must be replaced after the cause of failure has been rectified.
A stock should always be kept with the jetter and only genuine replacement parts should be used in the pressure disc holder. The adaptor and holder should be checked regularly for signs of leakage. A worn adaptor or holder could lead to premature disc failure.