Low water pressure can make even the simplest household tasks feel like a chore. Whether your house water pressure is low throughout the entire home or just at a single faucet, the cause usually boils down to a few specific culprits. Here is a breakdown of what causes low water pressure in a house and how to address it.
A Faulty Pressure Reducing Valve (PRV)
Most homes have a bell-shaped valve located near the main water shut-off. This is the Pressure Reducing Valve (PRV). Its job is to slow down high-pressure city water so it doesn’t damage your pipes. When a PRV fails, it often defaults to a “low” setting, causing a significant and often sudden drop in water pressure across the entire house.
Partially Closed Main Shut-Off Valve
If you’ve recently had plumbing work done, your main water valve may not have been opened all the way. Even a slight turn away from the “fully open” position can starve your home of the volume it needs, making the pressure feel weak at every fixture.
Mineral Buildup and Pipe Corrosion
In areas with hard water, minerals like calcium and magnesium build up inside your pipes over time. In older homes with galvanized steel pipes, internal rust (corrosion) can narrow the opening of the pipe to the size of a pinhole. This is the primary cause of a gradual decline in water pressure over several years.
Water Heater Sediment
If you notice that your water pressure is low only when using hot water, the problem is likely inside your water heater. Sediment buildup at the bottom of the tank can block the hot water outlet, restricting flow to your showers and sinks.
Hidden Leaks or Water Main Breaks
A major leak is often the reason water pressure is low in a house suddenly. If a pipe bursts in a crawlspace or underground, the water is diverted away from your faucets. If you see damp spots on walls or your water meter is spinning while no fixtures are on, you have a leak.
3 Quick DIY Checks
Before calling a professional, run these three tests to narrow down the source of the problem:
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Test the Aerators:
Unscrew the tip of your faucet. If the pressure is strong without the aerator, it just needs a vinegar soak to clear mineral deposits.
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Compare Hot vs. Cold:
If cold water is strong but hot water is weak, focus on the water heater.
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Talk to Neighbors:
If the whole block has low pressure, the issue is a municipal water main break or city maintenance.
If these checks don’t reveal a simple fix, the problem is likely structural or mechanical. At this stage, attempting to “DIY” a fix on a PRV or a main line can lead to further damage.
When to Call Arnold & Sons for Professional Assistance
Some water pressure problems require specialized gauges and technical expertise to solve without causing further leaks. You should contact a professional if:
- The pressure drop is house-wide and unexplained.
- You suspect a hidden leak or see an unexplained jump in your water bill.
- Your home has old galvanized pipes and likely needs repiping.
- You need a professional water heater flush to clear sediment.
Stop guessing and start flowing. Schedule a Professional Diagnostic with Arnold & Sons today.
