Why Is My Water Pressure Low?

If low pressure is at one faucet or shower, the cause is usually a clogged aerator, showerhead, or cartridge, which costs little or nothing to fix. If it is the whole house, the likely causes are a partly closed shutoff valve, a failing pressure reducing valve, a hidden leak, or an issue on the supply side.

Narrow it down first

Where the low pressure shows up tells you most of what you need to know. Check a few faucets around the house before you start taking anything apart.

• One faucet or shower only. The problem is at that fixture: its aerator, showerhead, cartridge, or the small stop valve under the sink. This is the most common case and usually the cheapest.

• Hot water only, everywhere. Look at the water heater. A partly closed valve on its supply line or sediment buildup in a tank can restrict hot water flow. If you have a tankless unit, scale inside it can do the same.

• The whole house, hot and cold. Look at the main shutoff valve, the pressure reducing valve if your home has one, and the water meter. Ask a neighbor whether their pressure dropped too. If it did, the cause may be on the utility side.

• It comes and goes. Pressure that dips when another fixture runs is often undersized or aging pipes. Pressure that pulses on a well system usually points to the pressure tank or switch.

How to test your water pressure

A screw-on pressure gauge costs about $10-$15 at a hardware store. Thread it onto an outdoor faucet or the washing machine hookup, make sure no other water is running, and open the faucet fully.

• Roughly 40 to 80 psi is a commonly cited normal range for homes.
• Below about 40 psi tends to feel weak, especially upstairs or with two fixtures running.
• Above about 80 psi is worth talking to a plumber about, even if the pressure feels great. High pressure is hard on water heaters, toilet valves, and supply lines, and it is a common cause of banging pipes.

If you are on a well, the gauge on or near the pressure tank shows the same thing. Readings that climb and fall in a tight cycle every few seconds are a sign the pressure tank is not working right.

Fixes you can do yourself

• Clean the aerator. Unscrew the tip of the faucet (wrap it in a rag if you need pliers), rinse out any grit, and soak scale off in white vinegar for an hour. Replacements cost a few dollars if it is damaged.

• Soak or replace the showerhead. Mineral deposits block the small holes. Soak it in vinegar overnight, or tie a bag of vinegar around it. Some showerheads also have a flow restrictor that can clog.

• Open the valves fully. Check the stop valves under the sink, the valve on the water heater supply, and the main shutoff. Turn each fully open, then back off a quarter turn so it does not stick.

• Check the meter for a leak. Turn off every faucet and appliance that uses water, then watch the meter for 15 to 30 minutes. If it moves, water is going somewhere. A running toilet is the most common culprit, so check those first.

• Flush the water heater (if you have a tank). If the problem is hot water only, draining a few gallons can clear sediment near the outlet.