Manual Flush Valve Locking Devices, Package Quantity 12 Manual flush-valve covers enclose the top of a flush valve (flushometer) to keep out debris and help maintain proper pressure within the valve. Outside covers are metal caps that help seal the valve's upper chamber. Inside covers are plastic or rubber caps that form a seal between the valve diaphragm and the outside cover. These outside and inside covers are commonly used as replacement covers to fix problems such as water leaking into the fixture or from the top of the valve, toilets that keep running, or flushes that are too long or too short.
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