Water pressure that has "gradually gotten worse" is one of the more common complaints plumbers hear — and it's rarely one single thing. In a recent service visit, a homeowner described exactly this: pressure that used to be strong but had slowly faded over time, with no obvious leaks or water damage anywhere in the house. Here's how a licensed plumber works through that kind of problem, and what it can reveal about the condition of your water heater and fixtures.
Start With the Easy Checks: the Jeneral Plumbing technicians
Before diagnosing a pressure complaint, a technician will typically locate and test the main shutoffs — including any separate valve for irrigation lines, which can sometimes be mistaken for a house shutoff. Getting these straight matters, especially in an emergency where you need to shut off water quickly to limit damage.
From there, checking the inside of a toilet tank is a simple but telling step. Brown or black sediment built up around the fill valve and flush mechanism can indicate mineral buildup in the water supply, and that same sediment can clog fixtures throughout a home — not just the toilet in question. In this case, a small amount of sediment was visible near the base of the tank, which can accumulate gradually and affect flow at multiple fixtures over time.
Safety note: if you ever need to clean inside a toilet tank or work on fill valves yourself, avoid flushing with hot water after using descaling products like citric acid — sudden temperature changes can crack porcelain. For anything beyond basic cleaning, it's best to have a licensed plumber inspect and service the components.
Thermal Expansion Tanks: A Common Installation Oversight
One finding during this visit was a thermal expansion tank mounted above the water heater that wasn't functioning as intended. Expansion tanks exist because homes with a check valve (a code requirement that stops water from flowing backward into the street) create a "closed" plumbing system. When a water heater heats water, that water expands, and with nowhere else to go, the expansion tank is designed to absorb that extra volume.
For the tank to work, it needs to be pre-charged with air pressure that matches the household's water pressure. Expansion tanks typically ship from the factory with a standard air charge, but if a house runs at a different pressure, a technician needs to add or adjust the air charge to match. In this case, that step appeared to have been missed when the tank was installed, meaning the tank wasn't absorbing any thermal expansion. Left unaddressed, this doesn't necessarily affect household water pressure, but it can shorten the life of the expansion tank itself and put unnecessary strain on the water heater and system over time.
Correcting this involves draining down pressure in the house and recharging the tank — not a job for guesswork, since it ties directly into your water heater and backflow prevention setup. If you're unsure whether your expansion tank is doing its job, it's worth having a professional check it as part of routine water heater service.
Worn Valve Washers Can Also Cause Leaks
Supply valves under fixtures — like the ones feeding a dishwasher or sink — rely on a rubber O-ring to seal properly. Over time, that washer can tear or wear down, causing a leak right at the valve when it's turned. The fix is straightforward for a professional: rebuilding the valve by replacing the worn O-ring internals so the valve seals like new again.
When to Call a Professional
Gradual pressure loss, sediment in your fixtures, and a non-functioning expansion tank are all things that build up slowly and are easy to overlook — until a bigger issue develops. If you're noticing weaker pressure at your sink or shower, don't assume it will resolve on its own. A licensed plumber can check your shutoffs, inspect your toilet tanks for sediment, and verify your expansion tank is properly charged, all as part of a standard visit.
Jeneral Plumbing offers routine inspections through our service plans, and if a fixture issue turns out to need more than a quick valve rebuild, our fixture repair team can take care of it.
Call Jeneral Plumbing
If your home's water pressure has been quietly getting worse, or you're not sure whether your water heater's expansion tank is working properly, give Jeneral Plumbing a call at (978) 392-7789. Regular-hours visits carry an $80 dispatch fee — the cost of the visit, waived when you hire us for the work.
This post is for informational purposes only and is not a substitute for an in-person evaluation by a licensed plumbing professional.
Written by Sierra Sorongon.
This article was drafted with AI writing tools and edited before publication. AI tools did not inspect any job or validate technical conclusions.
Last updated .