High water pressure can be a problem

Q: A plumber came out recently for an unrelated problem and, when checking my water pressure, noted that it was 95 and should be in the 60 to 80 range. He suggested a new pressure regulator — at a cost of $350.

My water pressure probably changed due to the addition of new housing developments all around me. My questions:

Is this a problem for me to have high pressure? Will my pipes burst?

What about appliances like the refrigerator? What about the extra pressure on faucet fixtures?

: Water pressure is a problem if it is too high, true. Excess pressure can cause shortened water-heater life and failure of the dishwasher solenoid valve, and it is harder on the icemaker, faucets, fixtures and the whole plumbing system in general.

You are more likely to suffer water hammer as well. Especially vulnerable are older steel and flexible plastic pipes used for icemakers and water-purification systems.

Your plumber is right; anything above 80 psi (pounds per square inch) is too high and in fact requires a pressure-reducing valve under code.

But 95 psi is not exceptionally high, and I can tell you millions of homes have had water pressure above the recommended mark for decades, suffering no ill effects.

So I would consider it a very low risk at 95 psi. Quite possibly your water heater will not last as long, or a pinhole may develop in a pipe before it would otherwise.

Adding a pressure-reducing valve without an integral bypass makes the plumbing system "closed."

Complicating matters greatly, again under code, a closed plumbing system needs an expansion tank (basketball-sized steel tank with a bladder) mounted on the water heater to take up the extra strain you are putting on the water heater and plumbing system.

Water pressure is a function of the water utility serving the home. You have no control over it. Pressure can vary slightly depending on your home's relation to hills, reservoirs and pumps.

Water pressure delivered to your home can change from what it is at the meter.

My own house sits roughly 40 feet below the meter in the street. Adding the rule of thumb of half-pound pressure rise (or fall) per vertical foot, pressure at my bathroom is 20 pounds higher than delivered by the utility.

The reverse is true in multi-story buildings, which is why they are engineered to overcome this problem.

But the real story about the plumbing system is how it affects the occupants in the shower. Nobody likes a weak shower. The classic misconception is that a weak shower is the result of low water pressure.

Not so. Water flow is key. Flow is directly related to pipe size, with only a very loose association with pressure.

Give me big pipes and low pressure over high pressure and constricted (or undersized) pipes every day.

That's the theory of water-saving showerheads — small orifices allow only a predetermined amount of water to get through, despite the pressure or lack thereof.

Darrell Hay is a local home inspector and manages several rental properties. Send questions to dhay@seattletimes .com or call 206-464-8514.