Many Causes, Many Fixes For Low Water Flow

Q: I am considering buying a 39-year-old home in Shoreline with low water pressure. Portions of the plumbing have been replaced with copper and plastic. Some of the original galvanized plumbing is still in use and in good condition, my home inspector says. Are there devices that can be used to increase the pressure?

A: When homeowners complain about lack of water pressure, it is almost without exception a lack of flow rather than pressure. Normal water pressure is generally 60-90 PSI (pounds per square inch). The water pressure delivered to your home is determined by the utility serving you. It is a condition determined by where you are in relation to other users, pumps and reservoirs.

I've seen several brand-new homes with between 30 and 35 PSI that have no signs of unsatisfactory conditions. I check water pressure only to make sure there is not an overpressure situation. Too much pressure can damage older plumbing joints and appliance and fixture valves and can contribute to water hammer (the loud bang when valves are closed abruptly). Having too little pressure is not usually a problem unless the pressure is severely low. Talk to the water utility folks in that case.

What can cause a low flow then? Any type of constriction in the piping system from the meter to the faucet aerator, including undersized lines.

First thing to check is all the valves. The check the meter, the main shutoff at the house, the water heater, the angle stop valves at each fixture, and finally make sure a a pressure-reducing valve has not been installed that is not adjusted properly. Newer fixtures have flow-restriction devices built into the faucet heads.

Your galvanized pipes are the next likely culprit. Galvanized pipes have a tendency to build up mineral deposits. These build-ups restrict flow more every year until they are replaced. The horizontal pipe sections are affected early, and sections buried in the dirt are affected first because of chemical reactions with the soil.

Usually when pipe buildups are large, replacing the water service from the meter to the home with copper or plastic is enough to restore adequate flow. A plumber can do a flow check to see if this is the case.

It is also possible that previously replaced water service or interior lines are undersized. Again, a plumber could determine this for you.

Yes, there are devices that can increase the pressure in your lines. These pumps would need to be coupled with pressure tanks similar to what well systems have, or the pumps would need to cycle on every time the water came on. You would have increased pressure but decreased water flow.

The laws of fluid dynamics, which make jet engines and pressure washers work, apply to the plumbing system as well. In a given pipe size, with an increase in volume comes a decrease in pressure. In other words, you could actually get more flow from your pipes by decreasing the pressure.

Q: I'm having my roof replaced on my home, and the roofer suggested I get a continuous ridge vent. Wouldn't this make the home harder to heat in the winter? What does this do, and is it really worth the extra $255 he wants to do it?

A: Absolutely worth every penny. Ridge vents work in conjunction with your eave vents to dissipate heat buildup in the summer and the massive amounts of condensation in the winter. Vents at the top and bottom of the roof plane provide optimum venting naturally, by convection.

A well-vented attic or rafter space adds many years to the life of the roofing materials and keeps the house cooler in the summer. And ridge vents don't make homes harder to heat in the winter. The ventilation provided is on the cold side of the insulation, not the warm side, where heat loss would occur.

Building codes require the area of roof ventilation to be 1/150th of the area to be ventilated. Ridge vents are so effective that when they are installed in new homes, that required number is halved. Ask The Expert answers readers' questions every Saturday. Send questions to Ask The Expert, Seattle Times, P.O. Box 70, Seattle, WA 98111, or call 206-464-8514 to leave your questions on Ask The Expert's recorded line. E-mail address is dhay@seattletimes.com