Water Line Repair & Replacement
Repair or replace the pipe that carries water from the meter into the house.
Plumbing guide
Low Water Pressure in the House: Causes and Fixes
Where the pressure is weak tells you most of what you need to know. One tap points to the tap. Every tap points to something at the front of the house.
By the Urban Comfort Plumbing team ·
Start by asking where it is weak
Walk through the house and run each tap, shower and hose spigot. If only one fixture is weak, the problem is local to that fixture. If hot water is weak and cold is fine, the problem is in the water heater or the hot lines. If every fixture is weak, the cause is in the main supply, the pressure regulator or the pipe leading into the house.
Also note when it started. A sudden drop right after plumbing or street work points to a valve left partly closed or debris stirred up in the line. A slow decline over months points to buildup inside old pipe.
Causes at a single fixture
The most common cause is a clogged aerator, the small screen at the tip of a faucet. Minerals and sediment collect in it and restrict flow. Unscrew the aerator, rinse it, and soak it in vinegar if it is crusty. A showerhead clogs the same way, and soaking it in vinegar clears mineral scale.
If cleaning does not help, check the shutoff valve under the sink. A valve that is only partly open throttles the flow. A kinked or aged supply hose can do the same. Inside the faucet, a worn cartridge can restrict flow too. These problems are covered under faucet and sink repair.
Causes in the whole house
Start at the main shutoff valve for the house. If it is not fully open, the pressure drops everywhere. Gate-style valves, with a round wheel, sometimes fail internally even when they appear open. Next, look at the pressure regulator, a bell-shaped valve often found near where the water line enters the house. A regulator that has failed can reduce pressure too far or let it climb too high.
A pressure gauge that screws onto a hose spigot shows the actual pressure. Typical home pressure falls in a band of roughly 40 to 80 psi. Readings far below that suggest a regulator or supply problem, and readings far above it risk damage to fixtures and appliances.
Filters, softeners and water heaters
A whole-house filter with a clogged cartridge restricts flow to the entire house. If the pressure dropped around the time the filter was last changed, or long after it should have been, start there. A water softener with a failed valve can also throttle flow, and the bypass valve lets you check whether it is the cause. See water filtration for how cartridges are changed.
A water heater full of sediment can reduce hot water flow, and corroded fittings at the heater can restrict it as well. Compare hot and cold at the same tap. If only hot is weak, look at the heater first.
Old pipes and hidden leaks
Galvanized steel pipe corrodes from the inside. Rust builds up on the pipe wall and narrows the opening, and pressure falls over the years. A house with galvanized lines and a slow, steady decline is a candidate for repiping.
A leak lets water escape before it reaches the fixtures. A drop in pressure with a rising water bill, or a wet patch in the yard, points to a leak on the line from the meter to the house. See water line repair and leak detection.
The city side
Sometimes the weakness is not in your house. A water main break, flushing of hydrants, or heavy demand can drop pressure for a neighborhood for a while. If neighbors report the same problem, call the water utility. A drop that lasts a few hours and recovers is usually a utility issue, and a drop that stays is more likely yours.
If the pressure is low only at certain times of day, heavy demand in the area may be the cause. A gauge left on a spigot overnight with a simple log shows the pattern.
How to test the pressure yourself
Buy a pressure gauge with a hose-thread fitting. It costs little and screws onto an outdoor spigot or the washing machine connection. Make sure no water is running in the house, attach the gauge, open the spigot fully and read the dial. Many gauges have a trailing needle that records the highest reading, which is useful for catching spikes at night.
Take readings at different times of day, since pressure can swing with neighborhood demand. Write the numbers down. A plumber will ask for them, and they help separate a supply problem from a problem inside the house.
Pressure that is too high
High pressure causes its own damage, even if it feels great in the shower. It strains washing machine hoses, toilet fill valves and water heater connections, and it is a common reason for banging pipes and leaking joints. If the gauge reads well above the normal range, the regulator is probably failing and should be replaced.
A new regulator often costs less than the damage that high pressure causes over a year. An expansion tank on the water heater also helps absorb pressure swings when the system has a check valve.
Hot water only
If only the hot side is weak, the water heater is the first place to look. Sediment inside the tank can block the outlet, and a partly closed shutoff valve on the hot line throttles flow. A tankless heater with scale in its heat exchanger gives reduced flow too. Flushing the tank, or descaling a tankless unit, often restores it. See tankless service for how descaling works.
When to call a plumber
If you have cleaned the aerators, checked the valves and the cartridge and the pressure is still low, it is time to call. Tell the plumber where it is weak, when it began, what the gauge shows and whether the bill has changed. That points the visit in the right direction.
A plumber can test pressure, check the regulator, look for leaks and judge the condition of the pipe. If the problem is the supply line or old pipe, the repair may be larger, and the plumber can explain the options and what each costs.
Common questions
Low water pressure questions
A typical range is roughly 40 to 80 psi. A gauge on an outdoor spigot shows yours.
Mineral buildup in the showerhead is the most common cause. Soak it in vinegar and rinse it, and check the shower valve if that does not help.
Yes. A leak on the line before the house reduces what reaches the fixtures. A rising bill is another clue.
Some regulators have an adjusting screw, but a mistake can damage fixtures. A plumber can test and set it.
Related services
Repiping & Whole-Home Pipe Replacement
Replace worn galvanized, copper or older plastic pipe through the whole house.
Faucet & Sink Repair
Repair drips, weak flow, stuck shutoff valves and leaking outdoor spigots.
Pressure weak everywhere?
Call and tell the dispatcher where it is low and when it began.