The reason there are two shutoff valves is that the pressure relief valve does not have its own return line to the water supply tank. It uses the return line for the water flow test. The pressure relief valve is connected to the test line before the flow meter and there is a shutoff valve after the flow meter which is needed for testing. In addition to this shutoff valve there is a second one between the discharge of the pressure relief valve and the test line. Fire Ready recommends that a separate pipe be installed for the relief valve and when doing this remove the shutoff valve on the on the discharge side of the pressure relief valve.
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