Question:
I have a problem that is driving me crazy. I can’t figure it out and am about to call a plumber. I thought to try asking you first, in hopes that I may save a bundle of money on a plumber. Hoping you can help.
There is a terrible knocking sound whenever someone uses one particular bathroom in our home. I don’t know where to begin. Is this something I can investigate on my own and maybe fix? Is this common?
– Rich C.
Answer: Rich, the hammering is typically due to one of two things: one, a pipe is not strapped properly in a wall within the home, or two (most likely), there is too high a pressure with the pressure reducing valve.
The PRV cannot be set higher than 80 pounds, per the UPC (uniform plumbing code). The ideal setting is 65 pounds, which allows proper flow and pressure. If you set it too high, it wastes water and, if high enough, causes damage. When the PRV goes bad, the pressure that goes into the home is whatever the city is providing.
Depending on where you are in the city, the pressure can be as high as 100 pounds per square inch. If the PRV is bad and the pressure entering the home is not stepped down, this can blow plastic ice maker lines, washing machine lines and toilet valves.
In the case of your complaint, the hammering noise, this can also be the culprit. The first thing I recommend is to go to a big-box store and purchase a water pressure gauge, approximately $20, and attach it to a hose bib. This will show you what the water pressure is, entering the home. If it’s over 80 PSI you can try to see if the gauge will respond and go down. If not, it’s time to replace the PRV. Good luck.
Robert Lamoureux has more than 40 years of experience as a general contractor, with separate licenses in electrical and plumbing contracting. He owns IMS Construction Inc. in Valencia. His opinions are his own, not necessarily those of The Signal. Opinions expressed in this column are not meant to replace the recommendations of a qualified contractor after that contractor has made a thorough visual inspection. Email questions to Robert at [email protected].
