Knowing the flow rate of each hot-water outlet can help you understand the layout of an existing hot-water distribution system without seeing the pipes. It might come in handy, for example, if you were trying to decide whether an under-sink circulating pump would satisfy a homeowner’s complaint about having to wait too long for hot water. Here’s how to test the system.
1. Fixture flow rate. Focusing on sinks and showers one fixture at a time, turn the hot tap on full and capture the water for 15 seconds. Measure the volume in gallons (16 cups per gallon), and multiply the result by 4. This is the flow rate in gallons per minute for each fixture.
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