Test Port -

A test port/test header is the most common method for testing fire system performance. A connection on the discharge side of the fire pump routes water out of the system through a test header which carries an array of hose-valves. Each valve is capable of flowing around 300GPM, the actual number of valves required for a given flow is stipulated in NFPA-20. A pitot tube is used to measure the water flow from each valve and then calculate the system's performance.

Flow Loop -

A flow loop is a piping configuration that allows for fire system testing without flowing water out of the system. Instead of routing water through a hose-valve header it is instead directed through a flow meter and returned to the suction side of the fire pump to be cycled back through the system. This method of testing has a few drawbacks; it doesn't test the water available from the suction supply, and the flow meter itself can go out of calibration. On the plus side, a flow loop doesn't waste water (for a high capacity pump water waste can come to thousands of gallons) and you won't turn your parking lot/property into a swimming pool. Flow loops are commonly paired with test headers to ensure proper calibration of the flow meter.

City Bypass -

A city bypass loop is a piping configuration that allows water from the suction supply to bypass the fire pump itself and ties into the far end of the system discharge. NFPA-20 stipulates that if the suction supply is great enough to be of material use a city by-pass loop shall (NFPA-speak for mandatory) be installed. "Material use" is not defined but is taken to mean a suction pressure that is high enough to run at least a couple of sprinkler heads without the aid of a pump. The intent of a bypass is to provide some fire protection in the case of pump system failure, or of a fire occuring while the system is shut down for maintenance.

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