Flow rate and static pressure (check both?)

[Richard Moore]

There was a “driftâ€

[Brandon Chew]

I check both. I don't think you get a complete picture of the supply system without doing so.

Flow rate at any fixture is a function of the inside diameter of the pipe and the velocity of the water flowing through it at that point in the system. Pressure is the driving force pushing the water through the system and friction is trying to slow it down.

You can have a faucet that has a good flow rate at what seems to be a reasonable pressure (at the faucet), but due to restrictions somewhere in the piping system a very high pressure is needed on the upstream side of the restriction to make it so.

Since we know that high pressure on the house supply plumbing can cause problems, it makes sense to measure pressure coming into the house as well as the flow rate coming out of the fixtures.

[John Dirks Jr]

I think it's a good idea to check the pressure, especially to make sure it's not to high. High readings could indicate a water heater problem even when you test the pressure on a cold side hose bib.

If the thermostat for the water heater is not shutting down the burner or element, the water can heat beyond a safe point and thus the pressure in the heater and throughout the supply system can be increased by the overheated water.

Take high line pressure to begin with and then add that to a malfunctioning water heater thermostat and the risk of someone getting burned by a TPR valve release is increased.

Gauges are cheap and the test takes about 30 seconds. Why not just do it?

BTW, I also test and report on the temperature of the hot water at the fixture nearest to the water heater.