How difficult can it be to figure out what a house’s water pressure is?
It is a good thing taking one’s own blood pressure is not as difficult.
One of the first things I do around the exterior of the home is test the water pressure at the first outside faucet I come to. They all get checked eventually. At a recent inspection the first faucet had a pressure of 120 psi–a wee bit high.
I usually recommend that the house water pressure be set below 80 psi, and it is fairly routine to recommend installation of a pressure regulator on the piping when I find pressures this high. Knowing the area this house was in, and having not seen water pressure this high before, I began to suspect there might be other issues, so I took off the test gauge and ran the water a few seconds and then re-tested the pressure. This time it tested at a more normal 65 psi.
I was not surprised–I see this condition quite frequently.
Before I go into the reasons for this condition I want to point out about the importance of inspection protocols. I like to do this first pressure test prior to running any water for the exact reason that the high pressure would not have been noted had the pressure been relieved by running the water first. Of course if someone is living in the home it is a moot point, but this condition is quite common in houses that have been vacant for a while. This one had been vacant for several months.
When I find this condition, it is a guarantee that there is some sort of back-flow protection on the system–possibly even a pressure regulator on the system without a thermal expansion device (tank). Some newer water meters being installed have built in back-flow protection. Many jurisdictions are changing out the older style meters with these newer type meters. Without this back-flow protection, any expansion of the water due to heating of the water used to be simply absorbed by the city water supply. It leads me to wonder if the local water utilities are notifying home owners when they change out the meters–and recommending installation of expansion tanks.
Sure enough, there was no expansion device on this system. As the water heater sat heating away in the months while the house was vacant, the pressure was slowly building up in the system. It is really a pretty easy fix–as simple as installing an expansion tank on the system. All of this is why modern installations of water heaters all require some means of protecting the system against the buildup of undesirable pressure within the piping when a means of back-flow protection is present.
High water pressure can damage sensitive electronic valves, water shut-offs and other plumbing fittings–not to mention waste water. Water conservation guidelines call for water pressure to be set below 70 psi.
So now you can see that figuring out what the water pressure is at the home is a little more complicated than just sticking a pressure gauge on a faucet and reading the gauge.
I know my own blood pressure is better now—how about yours—and how come humans don’t come with expansion tanks?
I certainly know a few that could use one.
By Charles Buell, Real Estate Inspections in Seattle
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Good info as usual, thanx
I agree with Jeff, good info as always. In the second full paragraph you mentioned recommending a pressure regulator under conditions of high water pressure. Do pressure regulators have a backflow device or would one need to be installed upstream of the new pressure regulator so that it doesn’t introduce pollutants to the public system?
Justin, most pressure regulators have enough back flow protection that an expansion tank is necessary—they are not typically considered back flow preventers. If you are looking to accomplish that, there are devices specifically for that.