The shower that used to sting a little now dribbles, and rinsing shampoo out takes twice as long as it should. Or the kitchen faucet is fine but the hall bathroom is weak. Or everything in the house went soft overnight. Low water pressure in a house is a complaint with maybe eight real causes, and the fastest way to find yours is not to look at the plumbing at all at first. It is to notice the pattern: which fixtures, hot or cold, and whether it happened slowly or all at once.
Spend five minutes on the pattern and you will know whether this is a ten minute fix at one faucet, a part on the main line, or a call that should not wait.
One fixture weak, everything else fine
If a single faucet or shower is the problem and the rest of the house runs normally, the cause is at that fixture. In Las Vegas that almost always means mineral scale. Our water carries a heavy load of dissolved calcium, and it plates out wherever water sits still or passes through a small opening. The aerator screen on a faucet and the tiny nozzles on a showerhead are exactly that.
Unscrew the aerator from the end of the faucet spout (a rag and gentle pressure with pliers if it is tight) and look at the screen. If it is crusted white or packed with grit, soak it in white vinegar for an hour, scrub it with an old toothbrush and screw it back on. The same soak works for a showerhead, either removed or with a bag of vinegar tied over it. The Las Vegas hard water post explains why you will be doing this again in a year.
If the aerator is clean and the fixture is still weak, the cartridge inside the faucet or shower valve may be clogged or partially failed, or a supply stop under the sink may be only half open. Check the small valves under the sink first; they get bumped. A cartridge replacement is a plumber-level job on most shower valves, and a faucet or showerhead that has worn out from normal use is the kind of part a home warranty plumbing plan covers.
Low water pressure in the shower but not at the sink next to it
This one deserves its own paragraph because it fools people. A shower valve has a flow restrictor and often a pressure-balancing spool inside, and both are magnets for scale. Scale on the spool makes it stick, which can drop the pressure on one side or make the shower surge hot and cold. If cleaning the showerhead does not fix a weak shower, the valve cartridge is the next suspect, and in a home more than ten years old on unsoftened water, it is usually the answer.
Hot water weak, cold water fine
Turn on the cold at a sink and note the flow. Now turn it off and run the hot alone. If the hot side is noticeably weaker at every fixture, the restriction is between the water heater and the taps, which usually means the water heater itself. Sediment in the bottom of the tank can partially block the outlet, a scale-clogged heat trap nipple on top of the tank can throttle the flow, and on a tankless unit a scaled heat exchanger or a dirty inlet filter screen does the same thing.
A water heater that delivers weak hot water is often also delivering less of it and recovering more slowly. A flush helps a tank that is not too far gone; a tankless unit needs descaling. If the heater is old, weak hot flow is one more sign it is near the end.
Whole house weak, and it crept up over months
When every fixture is a little worse than it was a year ago, think about what every drop of water passes through: the main shutoff valve, the pressure regulator, a water softener if you have one, and the pipe itself.
Start at the main shutoff. In most Las Vegas homes it is near the hose bib at the front of the house, in the garage, or at a manifold. Gate valves can creep partly closed, and a valve someone turned off during a repair may never have been fully reopened. Open it all the way, then back it off a quarter turn.
Next is the pressure regulator, a bell-shaped brass fitting on the main line, usually right after the shutoff. Most homes here have one because street pressure can be high. Regulators wear out, and when they do, pressure can drift down over months. The symptom is a house that is weak everywhere, with a hose bib ahead of the regulator (if you have one) that still blasts. A plumber can put a gauge on a hose bib and read the pressure in seconds, and an inexpensive screw-on gauge from a hardware store lets you do the same before you call; a regulator that has dropped well below its setting, or will not adjust, is replaced rather than repaired.
A water softener that has failed or whose resin bed has fouled can also restrict flow across the whole house. Every softener has a bypass valve. Put it in bypass and run a few faucets. If pressure comes back, the softener is the restriction.
In older neighborhoods, galvanized steel pipe that has narrowed inside with rust and scale is the slow, permanent version of this problem. It cannot be cleaned, only replaced, and the flow gets worse every year.
Sudden low water pressure, everywhere, since this morning
A sudden change is a different list. First, check whether it is you or the street. Ask a neighbor, or look for utility crews or a hydrant being flushed nearby. The Las Vegas Valley Water District posts and notifies about planned work, and a main break can drop pressure across a block for hours.
If it is just your house, a pressure regulator can fail suddenly as well as slowly. A main shutoff may have been turned down by someone working outside. And a leak, especially a big one, pulls pressure down at every fixture while the water goes somewhere it should not. Walk the house and yard: wet spots on the floor, a warm patch on a tile floor, a soggy section of lawn or gravel, a water meter dial turning with every tap closed. If you find running water with nothing on, shut the main and call a plumber; that pattern is exactly what the under slab leak coverage page exists for, and it should not wait.
One more sudden cause that is easy to miss: a burst or kinked flexible supply line to a single appliance can leak inside a wall or under a cabinet. The washing machine hoses and the refrigerator water line are the usual ones.
Pressure, flow and the difference that matters
Two things get called "pressure," and they are not the same. Pressure is the force in the pipe when nothing is running; flow is how much water comes out when something is. A clogged aerator kills flow but not pressure. A failing regulator drops pressure, and flow follows. A plumber will usually check both, and if your pressure is fine but flow is poor, the restriction is downstream of the gauge, which narrows the search considerably.
High pressure is its own problem, and worth mentioning because the fix is the same part. A regulator that fails in the open direction lets street pressure into the house, which bangs the pipes, stresses every valve and appliance connection, and makes the water heater's relief valve weep. If pressure went up rather than down, the regulator is still the first thing to check.
What a home warranty covers when the cause is a worn part
Many low-pressure fixes are maintenance: cleaning aerators, reopening a valve, bypassing a softener. The rest are failed components in the plumbing system, and that is where coverage applies. A Dwellness plan covers the home's plumbing system, including faucets, showerheads and shower arms and stoppages, in every plan from the Essential Plan up. When a cartridge, valve or fixture fails from normal wear and tear, you submit a service request online at any hour or call (702) 641-8888, pay the service fee for the visit, and a licensed local plumber handles the diagnosis.
The plumbing home warranty page describes what a typical plumbing claim covers. A few causes sit outside the plumbing system as a warranty defines it: water softeners are an optional add-on rather than base coverage, the exterior water service line between the meter and the house is also an add-on, and a utility-side pressure problem belongs to the water district. More than 85 percent of Dwellness claims are resolved on the first visit, and the plans do not require maintenance history to start. The plumbing maintenance tips post covers the habits that keep most of these problems from starting.
Weak water is annoying rather than alarming, right up until it is a leak. Read the pattern, do the easy fixes, and if the answer is a regulator, a cartridge or a tired heater, make it a service request rather than a project. Dwellness has covered Las Vegas plumbing systems since 1986, and it takes one quick call to (702) 509-7007, or a visit to dwellness.house, to request a free quote.