By Barry Stone
Dear Barry,
Since moving to our new home, we've had an annoying problem with the plumbing system. Whenever we flush the toilet or use the laundry, the shower pressure is reduced to a dribble. According to an article we read, this is usually caused by corrosion in old galvanized steel piping. But this house is brand new, and the water lines are all made of copper. We bought a pressure gauge from the hardware store and found the pressure to be about 65 pounds -- more than adequate, we've been told. So now we're scratching our heads and wondering about one other possibility. Our home is built on a flag lot, about 250 feet from the street. Could the unusual length of the main water line be causing our problem? -- Stan
Dear Stan,
You've done a good job of narrowing the list of possible causes for your plumbing problem. With new copper piping and 65 pounds of pressure, reduced water flow is most uncommon. The length of your main supply line could definitely be the cause.
The minimum pipe diameter for a residential water supply is 3/4 of an inch. The length at which this pipe dimension becomes inadequate depends upon the water pressure in the system and the number and type of water fixtures installed in the home. Even with few plumbing fixtures, a larger water supply pipe is likely to be needed for a run of 250 feet.
To determine the water supply requirement for your home, you'll need to compute the total number of fixture units in your home, and reference this information to the tables contained in the Uniform Plumbing Code. This kind of evaluation should be delegated to a licensed plumber. However, since your home is brand new, I recommend calling the matter to the attention of the contractor or builder responsible for the construction.
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