How to repair the diaphragm valve?
If the rubber diaphragm has worn out or its operation is disturbed by impurities in the water, turn off the water supply. Disassemble the valve putting the parts in the order in which they were removed, to facilitate subsequent assembly.
Wash the diaphragm in warm soapy water. If it is broken, replace it with a new one. Let the water run for a moment, to flush out any debris and put the diaphragm back in place – mount the valve.