Does This House Have Good Water Pressure?

Home Buying

Does This House Have Good Water Pressure?

A common question that my clients ask during home inspections is: “Does this house have good water pressure?”

Water pressure gauge
This water pressure gauge shows slightly high pressure of 85 PSI.

What they actually want to know is whether the flow from the showerhead will be strong enough for a quality shower, and whether someone flushing a toilet will interrupt that shower. Questions like these can’t be answered by examining water pressure on its own. Instead, we have to look at both water pressure and the resulting functional flow.

Water pressure is the amount of force from the water main into your home. Water pressure is measured in pounds per square inch (PSI), and normal water pressure is typically between 30 and 80 PSI.

Functional flow is the volume of water flowing through your pipes and arriving at individual fixtures. Poor functional flow may be due to buildups in the pipes or poor plumbing.

Perfect Pressure

You don’t want your home to have water pressure that is too low, but water pressure can also be too high. Piping systems are designed to have no more than 80 PSI. When you exceed this pressure it can cause problems. High pressure will rarely cause pipes to burst, but it stresses the weak links in your piping system such as rubber hoses and gaskets, making them vulnerable to leaks and failure.

pressure reducing valve
A pressure-reducing valve (the bell-shaped device seen here) can correct high pressure. Below the valve is a main water shutoff.

You can correct high water pressure by installing a pressure reducing valve. This is a bell-shaped device that reduces the water pressure. Aim for water pressure that is 60-70 PSI.

If the house has low pressure, you first want to determine if the house is on a public water supply system or a private well system. Most public systems are required to deliver a minimum of 30 PSI to your house, so inadequate pressure on public water systems is rare.

If the house is on a public water supply and the utility cannot improve your pressure, the solution involves installing a pressure tank and a pump. This gives your supply piping system a pressurized boost.

If the house is on a private well, poor pressure could indicate a problem with the captive storage tank and/or the pump and you should have the well system serviced by a qualified well expert.

Flaws in the Flow

rusted pipes
Rusted pipes can block water flow.

Poor functional flow can be an issue in old houses with galvanized steel pipe. This type of pipe was commonly installed until the late 1960s and early 1970s. This pipe was manufactured with a coating of galvanization that was designed to prevent corrosion of the steel pipes. When this galvanization wears off, the pipes occlude with rust. The result is a restricted piping system that will not deliver adequate water to the fixtures even with all the pressure in the world. To fix the problem, you’ll need to replace the pipes.

Another common cause of poor functional flow is unprofessional water piping systems. Good plumbers know how to size the pipes correctly so that adequate water is delivered to each fixture. An amateur mistake is running too many fixtures off of pipes that have too small a diameter. The result is inadequate water supply to fixtures or poor functional flow. This can be difficult to repair without piping replacement.

Just because a fixture has poor flow, don’t assume anything about the pipes yet. Other factors in the piping system can result in poor flow. Sometimes an angle stop (one of those shut offs below the sink) may be partly closed. Fixture aerators (the little screens inside the faucets) can become restricted. The main water shutoff to the house could be party closed or restricted. Supply connector hoses could be kinked or restricted.

Field Test

To determine whether a home has enough functional flow, go to the bathroom and turn on the sink and the shower. Wait for a satisfactory water temperature in the shower and then flush the toilet. See if the flow diminishes. You can go to other fixtures and run water too, but at some point every system will experience diminished flow if you open too many fixtures at once. One sure way to kill the flow is to open up an exterior hose bib during testing. I like to keep it simple and test flow by opening up every fixture in a given bathroom.

I hope this clears up some common misconceptions about water pressure and functional flow. Remember, informed homebuyers are happy homebuyers.

About Dylan Chalk
Dylan Chalk is a home inspector and the owner of Seattle-based Orca Inspection Services LLC – He is also the founder of ScribeWare software offering innovative and simple report writing solutions. Follow his house-hunting tips from the field on Twitter @ Or see his blog @

Note: This is a guest post; the views and opinions expressed are those of the author and do not necessarily reflect the opinion or position of Redfin.

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