Low Water Pressure In The House

Low water pressure is a symptom with a dozen possible causes, and homeowners usually start replacing parts before they know which one they have. Two questions eliminate most of the list in about five minutes, and they are worth answering carefully before you buy anything or call anyone.

The first question is how much of the house is affected. Walk around and run each fixture on its own - kitchen sink hot and cold separately, each bathroom, the tub, the laundry, an outside hose bib. One weak fixture with everything else normal is a fixture problem, and the whole rest of this page does not apply to you. Several fixtures weak in one area points to a branch line. Everything weak everywhere is a supply-side problem at the house.

The second question is whether it is hot, cold or both. Weak hot water only, with cold at full force, points at the water heater - a partially closed valve on the heater, a failed dip tube, or sediment and scale in a tank that has never been flushed. Weak cold only at a single fixture is often a cartridge or a stop valve. Weak on both at every fixture is the main supply, the pressure reducing valve, or the service line.

Write down what you find. The person who eventually quotes the work will ask exactly these questions, and answering them accurately is the difference between a diagnosis and an hour of billable hunting.

• One fixture, hot and cold both weak - that fixture's aerator, shower head, or its two stop valves
• One fixture, one temperature weak - a cartridge, a stop valve, or a kinked supply connector
• One bathroom or one side of the house weak - a branch line, often a partly closed valve or a corroded section
• Whole house weak, hot and cold - main shut-off, meter valve, pressure reducing valve, or the service line
• Whole house, hot only - the water heater, its shut-off, its dip tube, or sediment in the tank
• Pressure fine at first then fading while running - flow restriction rather than static pressure, often scale or an undersized line
• Pressure dropped suddenly over days with no change in the house - suspect a leak on the service line and have it checked

If the problem is one fixture, the cause is almost always something you can reach. Hard water is the reason: the North Texas Municipal Water District describes its treated water as moderately hard, and the City of Mesquite publishes an average of 93 to 134 milligrams per liter for its own supply, which the city converts to roughly 5.44 to 7.84 grains per gallon. Those minerals deposit in exactly the narrowest parts of the system - aerator screens, shower head jets, cartridge ports and angle stops.

1. Unscrew the faucet aerator and look at it. A screen packed with white or sandy grit is extremely common here. Soak it in white vinegar, brush it, rinse and refit. If it is damaged, replacements are inexpensive and sized by thread.
2. Do the same with the shower head. Many unscrew by hand; soak in vinegar, clear the jets, refit with fresh tape on the threads.
3. Check the two stop valves under the sink or behind the toilet. Multi-turn stops often sit half closed after a repair, and old gate-style stops seize part way. Open them fully and compare.
4. Check the flexible supply connector for a kink or a crushed section - behind a vanity this is easy to do and easy to miss.
5. If one temperature only is weak at a mixing faucet or shower, the cartridge is the usual suspect, and on a pressure-balancing shower valve the balancing spool can stick. That is a parts job rather than a cleaning job.
6. If the whole house is affected, go and look at the main shut-off and the valve at the meter box, and confirm both are fully open. A main that was closed for a repair and reopened three quarters of the way is a genuinely common cause and costs nothing to rule out.
7. Finally, if only hot water is weak everywhere, check the shut-off valve on top of the water heater is fully open before suspecting anything inside it.

If the whole house has gone weak and every valve is open, the pressure reducing valve is the next thing to look at. A PRV is a bell-shaped brass fitting usually found where the service line enters the house, often near the main shut-off, in a garage, a utility area or a box outside. Its job is to knock municipal supply pressure down to something the plumbing and the appliances can live with.

PRVs fail, and they tend to fail by drifting low rather than dramatically. The symptom is exactly what people describe as the house gradually losing pressure over months - showers that got weaker, a washing machine taking longer to fill, two fixtures that cannot be used at once. They are a wear item with a service life measured in years, not decades, and replacement is routine work for a plumber.

You can measure what is actually happening with an inexpensive pressure gauge that screws onto a hose bib. Run it with nothing else using water to get a static reading, then with a couple of fixtures open to see how far it falls. That single measurement tells a plumber more than any description, and it is the reading they will take themselves. If you get a number and it is far below what the rest of the street has, you have found your problem - and it is worth knowing that a PRV drifting the other way, high, is the cause of banging pipes, weeping relief valves on water heaters and premature fixture failures, so a reading is useful either way.

One thing not to do: adjusting a PRV by feel to get pressure back. The adjustment exists, but setting it without a gauge, and without knowing why it drifted, risks putting the whole house above what the system is designed for - and that is how you turn a weak shower into a leaking supply line.

Most low-pressure complaints are nuisances. One version of it is not: a sudden, unexplained drop in whole-house pressure can mean water is escaping from the service line between the meter and the house, which is where a significant part of a home's plumbing sits buried and unseen.

The signs worth acting on are specific. Pressure that fell over days rather than years. A patch of lawn that stays green or soggy in dry weather, or a wet area along the foundation. The sound of running water with every fixture closed. A water bill that jumped without a change in habits. And the simplest test of all: with everything in the house off, watch the meter - if the low-flow indicator is turning, water is going somewhere.

In this region that matters more than it would elsewhere. The expansive clay soils across the Dallas area shrink and swell with moisture, so a continuous underground leak keeps one area of ground moving while the rest dries, and the houses here are overwhelmingly slab-on-grade. A service line leak also raises the question of a slab leak, which presents differently - a warm spot on the floor, the sound of water under the slab, unexplained moisture at a floor edge - and is diagnosed with leak detection equipment rather than guesswork.

If you have a sudden pressure drop plus any of the signs above, close the main and get it looked at rather than waiting. Dallas Best Plumber is a free referral service, not a plumbing company. Tell us whether it is one fixture or the whole house, whether hot and cold are both affected, whether it happened suddenly, and your gauge reading if you have one, and we put your request in front of licensed, insured local plumbers who do leak detection and water line work, with a free, no-obligation quote. We never perform the work ourselves.

• Whole-house pressure fell over days, not years
• Soggy or unusually green ground in the yard or along the foundation
• Running water audible with every fixture closed
• The meter's low-flow indicator moves with all water off
• A water bill that rose with no change in use
• A warm patch on a floor, or moisture at a floor edge - possible slab leak

There is one cause that cannot be cleaned or adjusted. Houses built in the Dallas area before roughly the 1960s were commonly plumbed in galvanized steel, and galvanized pipe corrodes from the inside. The rust builds inward, the bore narrows, and the pressure at the fixtures falls steadily over decades. Where it has been partly replaced, the remaining original sections are usually the worst.

The tell is a house where every fixture is weak, the aerators are clean, the valves are open, the PRV reads normally, and running two things at once is impossible. Sometimes there is rusty water after the house has sat unused. Cleaning aerators in a galvanized house helps for a few months and then stops helping.

The remedy is repiping, in copper or PEX, and it is a real project - but it is also the only thing that works, and a partial repipe of the worst runs is a legitimate middle path. The reason to identify it early is that homeowners in this situation often spend years replacing fixtures and cartridges, which addresses none of it.

Pipe material by build era is a useful first filter across this market: pre-1960s often galvanized, 1960s to 1990s typically copper, and later builds increasingly PEX. If your house is in the oldest group and the pressure has never been good, get a plumber to open one section and look rather than continuing to treat the symptoms.