A Homeowner's Guide to Water Pressure

Water pressure is measured in pounds per square inch (psi) and is essentially the force at which the water exits the faucets. In most homes, the water pressure should fall between 30 to 80 PSI, though a more ideal range is about 40 to 60 psi. If the water pressure is too high, it can damage the plumbing fixtures, appliances, and pipes, leading to costly repairs.

If the water pressure is too low, your fixtures and appliances may not work properly. When this occurs, dishwashers and clothes washers cannot clean as effectively, faucets take a long time to fill a pot or cup, and you may have to stand directly under the showerhead to get wet. Use this homeowner's guide to water pressure to find out more about what water pressure is, how to test your home's water pressure, and how to troubleshoot low water pressure problems.

What is Water Pressure?

Before you test the water pressure in your home, it's a good idea to have some idea of what the term water pressure actually refers to. Generally, water pressure is understood as the force at which the water exits the faucet. This should not be mistaken with the flow, which is the amount of water passing through the pipe at any given time.

Water pressure is the force the pushes water through the pipes and is typically created by altitude or elevation. Water distribution systems will position large holding tanks in areas with a higher elevation than the homes that are being supplied with the water. The system takes advantage of gravity to increase the water pressure, though most towns and cities will also rely on pumps and pressure stations along the route to increase the water pressure to an acceptable level. Residential water pressure can fall between 30 and 80 psi, though the average for most homes is about 40 to 60 psi.

How to Test Your Home's Water Pressure

The easiest way to test the water pressure in your home is with an inexpensive water pressure gauge. You can find these devices online or at a local home improvement store. Make sure the all faucets and water-using appliances are turned off, then connect the water pressure gauge to your exterior hose bib or hose faucet. Turn the faucet on full and read the gauge to find out the home's water pressure.

In some cases, you may not have a hose faucet on the exterior of the home. Instead, you can disconnect the washing machine hose and connect the gauge to this faucet. Check to make sure the faucets and water-using appliances are turned off, then turn the faucet on full to get the home's water pressure reading in pounds per square inch (psi).

Low Water Pressure Problems

Partially Closed Valve

One of the most common issues that can lead to low water pressure problems is that the water is being obstructed by one or more partially closed shutoff valves. Typically, a home will have one main shutoff valve located inside the house. It can usually be found close to where the main water supply pipe enters the home. In some homes, there can also be a water meter valve. Depending on the local installation regulations, water meter valves may be located indoors, close to the main shutoff valve, or they may be outdoors inside a utility box.

If you suspect that a partially closed valve may be responsible for low water pressure in the home, simply locate all shutoff valves on the main water supply line. Operate each valve to ensure they are working properly. If you find any that are broken, leaking, or seized, speak to a plumber to have these valves replaced. then open each valve fully to restore water pressure to the home. Hire a plumber to replace any broken, leaking, or seized valves. If this does not resolve the problem, then there is likely a different reason for the low water pressure.

In many homes, there are two major shutoff valves controlling water to the home. The first is the water meter valve, located right next to the water meter on the main city supply pipe serving your home. Normally, you will not use this valve, as technically it belongs to the water company and is typically used only by water company personnel. But if your water pressure is low throughout your house, especially after some work has been done on your plumbing system, it's possible that this valve is not fully open.

• How to fix it: If you have recently had a repair done and are now noticing a reduction in the water pressure throughout your house, check the meter valve. It may be located on an outside wall of the house (in warm climates), in an underground box between the house and the street, or in an interior utility area, such as a basement or attached garage. The valve is fully open when the valve handle (which may be just a metal tab that is turned with a special wrench) is parallel to the water pipe. If the handle is set at an angle to the pipe, it is not fully open.
  

The other main shutoff valve is the home's shutoff, usually located inside the house, near where the main city supply pipe enters the home through the foundation wall. In warm climates, the main shutoff may be outdoors.

As with the water meter valve, this main shutoff valve is sometimes left partially closed after some kind of repair has been done to the system. If your water pressure has mysteriously lessened after a recent repair, there is a good chance that the valve wasn't fully opened after the repair was completed. ​​

• How to fix it: Make sure this valve is fully open. If this is a gate valve, indicated by a wheel-like handle, make sure the handle is turned fully in the counterclockwise direction. If it is a ball valve, indicated by a lever handle, the handle must be parallel to the pipe direction to be fully open.

Debris in the Pipes

A pipe blockage can easily interfere with water pressure. It may be caused by debris such as dirt, sand, solidified oil and grease, food particles, or foreign objects. Pollutants can block pipes if they back up due to fractures in the water main. Mineral buildup clogs pipes over time and causes the water pressure to go down, as there’s less space for water to travel through.

The first step is to clean out the aerator on your faucet. Sediment can easily get caught in there and no point in cleaning out your water lines and then leaving the sediment in the aerator.

To clean out the faucet's aerator simply follow these steps:

Place a towel in the sink to cover the drain.

Unscrew the tip of the faucet. If you can't do it with your hands, wrap a small towel or washcloth around it and then unscrew it with a wrench.

The aerator has 3 parts to it. Remove all three and remember how they go back in!

Rinse these parts with water.

Place everything back and screw the aerator back on.

You will want to repeat this process with all your faucets.

The next step then is to begin the process of cleaning the sediment out from your water lines. The simplest way to clean out water lines is to flush the pipes. You can easily do this by...

Opening three or four faucets (cold water only) at full force. Let them run for 20 minutes and you should see clear water.

If you do not, wait 30 minutes or so and repeat the process.

To add extra "oomph" - in addition to the indoor faucets running, turn on the outdoor hose at full force for 20 minutes as well.

Corroded Water Lines

Corrosion results in oxidation that collects on interior pipe walls, restricting the path for water to flow. Like mineral scaling, it is common in older galvanized steel pipes. Corroded pipe eventually develops holes until it fails completely.

The most serious and potentially expensive reason for low water pressure occurs when old galvanized steel water pipes are corroded to the point that water flow is significantly restricted. These pipes corrode on the inside (so you usually can't see the corrosion), but over time, the buildup of corrosion and scale gradually closes off the pipe.

This problem develops over decades, so the reduction in water flow is very gradual; you will not notice a sudden pressure drop. However, if you move into an old house with steel pipes, the pipes may have significant corrosion to start with and the problem may worsen relatively quickly.

• How to fix it: Unfortunately, the only solution for corroded pipes is to re-pipe the system with new copper or plastic water supply piping. It is the only way to solve the problem. Usually the best option for re-piping these days, in terms of cost and ease of installation, is to use PEX tubing rather than copper pipe.

Leaking Pipes

If your basement or foundation is flooded you already know your pipes are leaking. However, it doesn’t take a leak of that size to mess with your water pressure. The leak is misdirecting your water supply so that even if everything else is working properly, you’re not getting the full flow.

If you can access your pipes, go and take a look around and see if you find any wet spots or pooling water. Figure out which pipe is leaking and try a quick fix.

First, turn off your water supply and dry the outside of the leaky pipe as much as you can. Then, wrap a rubber patch around the spot that is cracked or corroded and use electrical tape and a pipe repair clamp to attach the rubber patch to the pipe.

This isn’t going to solve your problem for good, but it might prevent further damage for a few days. Even with a quick fix in place, call a plumber as soon as possible. Leaky pipes can damage your foundations but they can also contaminate your drinking water.

Truthfully, if you’re noticing a change in your water pressure as a result of leaky pipes, you’re probably dealing with more than one leak. It’s also possible that the leak is one of several things causing low water pressure.

Failing Pressure Regulator

Another common cause for home water pressure problems is a faulty pressure regulator or pressure-reducing valve. A pressure regulator is a control valve that reduces the input pressure in your plumbing system to a safe level that will not damage your pipes. Not all homes have them, but for those that do, a failing pressure regulator can cause a serious upward spike in water pressure. It can also have the opposite effect: sudden low water pressure. When the pressure regulator fails, you will notice the effect on all of the fixtures in the home, and it will happen rather suddenly. 

Faulty Fixtures

If you have low water pressure in all your plumbing fixtures, the issue is almost definitely with your water supply or your pipes. However, if it’s one or a few fixtures that seem to have a low flow, you may want to check out the fixtures.

The aerator on a faucet fixture is designed to reduce the volume of water coming from your faucet without altering the pressure. Over time, aerators can get bogged down with dirt and limestone build-ups or rust over.

Remove the aerators on your low-pressure faucets and see if they need cleaning. Once they’re completely clear of any buildup, put them back on and see if this makes a difference in your water pressure.

Fixtures, themselves, can become clogged. Because most fixtures aren’t particularly pricey, it may be a good idea to go ahead and replace them at this point. Before removing them, whether to clean or replace, turn off the water supply to that plumbing fixture.