Quick checks before you call
These take a few minutes and often narrow the problem down.
- Check whether the low pressure is at one fixture, several fixtures or the whole house.
- Compare hot and cold. If only hot is weak, the water heater or its valves are the likely cause.
- Unscrew the aerator on a weak faucet and rinse out any grit or scale.
- Make sure the main shutoff and the valve at the water meter are fully open, especially after recent work.
- Ask a neighbor whether their pressure dropped too. If it did, contact the water utility first.
What the pattern of low pressure tells you
Where the pressure is low points to where the problem is.
| What you notice | Likely cause | Typical fix |
|---|---|---|
| One faucet or shower is weak. | Clogged aerator, shower head or valve cartridge. | Clean or replace the part. |
| Only the hot side is weak. | Sediment in the water heater or a partly closed valve. | Flush the tank, open or replace the valve. |
| The whole house dropped suddenly. | Pressure reducing valve failure, a closed valve or a main break. | Replace the regulator, or call the utility. |
| The whole house got weaker over years. | Narrowed galvanized pipe or scale buildup. | Section replacement or repiping. |
| Pressure is low and the meter moves with taps off. | A leak on the supply line. | Find and repair the leak. |
How the pressure test works
The plumber screws a pressure gauge onto an outdoor spigot or the water heater drain and reads the static pressure with everything off. Then a few fixtures are opened to see how far it drops while water flows.
A good static reading with a big drop under flow points to a restriction inside the house, such as narrowed pipe or a partly closed valve. A low static reading points to the regulator, the service line or the supply from the street.
That one test usually tells the plumber which part of the system to look at next.
Pressure reducing valves
Many homes have a pressure reducing valve, or PRV, where the main line enters the house. It lowers street pressure to a level the fixtures and appliances can handle.
When a PRV wears out it can fail low, starving the house of pressure, or fail high, which strains supply lines and water heaters. Either way the fix is to replace the valve and set it to the right range. Inside Denton, the new valve is installed under the 2021 International Plumbing Code (IPC) the City adopted in 2022.
If your pressure swings up and down through the day, or a toilet fill valve hisses and a faucet bangs when it closes, the PRV is worth checking.
Old pipe, leaks and the service line
Galvanized steel supply pipe rusts from the inside and slowly closes up. Homes with it often lose pressure gradually over many years, and the cure is replacing the worst sections or repiping the house.
A leak on the buried line between the meter and the house can also cut pressure. The City of Denton's utility FAQ says a leak between the meter box and the house is the owner's to repair, which is water line repair work. A leak between the street and the meter box is the city's to fix.
Homes in Aubrey, Lake Dallas and other nearby towns may be on a different water provider. If the whole street lost pressure at once, call that provider first.
When it is the fixture, not the pipes
Low pressure at one tap is usually the tap itself. Scale and grit collect in aerators, shower heads and the cartridges inside single-handle faucets and shower valves.
Cleaning or replacing those parts is quick, and it is covered on the faucet and sink repair page. If cleaning only helps for a few weeks, the water may be carrying sediment or heavy minerals, and testing your tap is the next step.
What low water pressure repair costs depend on
These factors decide most of the price.
- Whether the cause is one fixture, a valve or the pipe itself.
- Replacing a pressure reducing valve versus cleaning or adjusting one.
- How much pipe is affected if galvanized pipe is the cause.
- Whether a hidden leak has to be found first.
You hear the price before any work starts.
Low water pressure questions
A sudden drop across the whole house usually means a failed pressure reducing valve, a valve that was partly closed during other work, or a problem on the utility side. Ask a neighbor, then check the valves.
Sediment in the water heater or a partly closed valve on the heater is the usual cause. A flush and a valve check often fix it.
A softener that is undersized or has a clogged resin bed or filter can restrict flow. Putting it in bypass for a minute shows whether it is the cause.
Only if the old head or its flow restrictor was the problem. If the whole house is weak, the cause is upstream.