Water Pressure Too Low

Water pressure too low or is it low functional flow

When it doesn’t seem like enough water is coming out of a sink faucet, showerhead, or sprinklers, we often say that the water pressure is too low. But in reality, it may not be the water pressure at all. It may be low functional flow.

What is water pressure? 

Water pressure is the amount of water pressure coming into the home from the city. It is measured in psi (pounds per square inch). Normally inspectors like to see that the water pressure is between 40 and 80 psi.

To discover what the water pressure is at your home, ask your home inspector, have a plumber measure it, or call the local water company and ask them. You can also simply get a $10 water pressure gauge from a local home improvement store, hook it to a hose bib, turn the hose bib on, and see what your water pressure is. Like many others, you may wonder if the size of the waterline will affect the water pressure. It doesn’t matter what the size of the waterline is, the pressure will be the same whether it’s a quarter-inch waterline or a 1-inch water line. On the other hand, the functional flow may be significantly different depending on the waterline size.

If the water pressure is low, there are several things you can check and do

First, check with the water department to see what the water pressure is in your area. They may have a pump down, they may be working on the system, or planning on increasing the pressure in your area.

If the house has a pressure regulator, check to see if it is set too low and if it is working properly. Sometimes, just adjusting the pressure setting will solve the problem. Pressure regulators have a tendency to wear out or stop functioning properly after a number of years.

If the city pressure is too low, then adding a booster pump to your water system may help. This is usually done by a plumber.

Low functional flow

Low functional flow is not having enough water flowing through your sink faucet, tub spout, or system.

First, check the following:

If the functional flow is low for the whole house, then check to see if the main valve at the meter is fully open and that the house shut-off valve is fully open. They may only be partially open.

If the functional flow is low at one or more fixtures, then check the small shut-off valve going to the fixture. This is sometimes called an angle stop. They may be only partially open.

Is the fixture a water conservation fixture? These have a much lower flow rate than older ones. Also, consider whether there an aerator on the end of the faucet that is clogged or needs cleaning.

In older homes, it may be due to corrosion or rust build-up in the galvanized piping.

Occasionally, the low functional flow may be due to the water pipe sizing, having too many fixtures on one line, or an obstruction in the waterline.

Home owners can normally make adjustments to a pressure regulator themselves. Plumbers and qualified handymen can likewise make adjustments to pressure regulators as well as do other work that may help improve pressure.

David Jones - General Contractor, Home Inspector, Consultant

David has over 45 years’ experience as a general contractor, inspector and professional instructor. He writes articles for homeowners, new home buyers and Real Estate Agents. Read more