LEARNING CENTER WATER LINES
Why is my water pressure suddenly low? (Louisville plumber’s checklist)
The short answer
Low water pressure usually traces to one fixable thing, not your whole plumbing. If it’s just one faucet, it’s almost always a clogged aerator (a free DIY fix) or a worn cartridge, usually $200–$300 to swap. If pressure dropped all over the house at once, first rule out the easy stuff: a half-closed main shutoff, a running toilet, or a pressure-reducing valve going bad ($600–$700 to replace). In Louisville, hard-water scale and older galvanized pipe are the usual long-term culprits.
Low pressure is one of those problems that feels like a big deal and usually isn’t. Before you picture repiping the whole house, the first question is simple: is it one fixture or the whole house? That one answer splits the whole diagnosis, and most of the time it points at a small part, not your pipes.
One faucet or shower: almost always a small clog
If the weak flow is at a single faucet or showerhead while everything else runs fine, the problem is right there at the fixture, not in your walls. Mineral scale from Louisville’s hard water builds up in the little screen and the valve, and it chokes the flow.
- Clogged aerator That little screen on the tip of the faucet catches scale and grit. Unscrew it, rinse it out or soak it in vinegar, and screwing it back on often fixes it in five minutes for free.
- Gunked-up showerhead Same story: soak it in vinegar overnight to dissolve the scale, or swap it. A weak shower is rarely a pipe problem.
- Worn faucet cartridge If cleaning the aerator doesn’t do it, the cartridge inside the faucet may be worn or scaled. Swapping it runs $200–$300, a small common part, not a big job.
The whole house dropped at once: work from easy to hard
When pressure falls off everywhere, don’t assume the worst. Run this list in order, the top items are free to check and catch most cases.
- A valve isn’t all the way open Check your main shutoff (usually where the water enters the house) and the meter-side valve. If someone bumped one half-closed after a repair, that alone can throttle the whole house. Open them fully.
- A toilet or fixture is running A silently running toilet or a stuck fill valve quietly bleeds off pressure and flow. Walk the house and listen; jiggle handles. Fixing the runner often restores everything.
- Pressure-reducing valve (PRV) going bad Many Louisville homes have a PRV near the main shutoff that keeps street pressure from being too high. When it fails, pressure sags house-wide. It’s a defined part we can test and replace for $600–$700, not a repipe.
- Hot-only? Look at the water heater If pressure is fine on cold but weak on hot, the culprit is usually sediment or a failing part in or near the water heater, not your supply lines.
- Old galvanized pipe In older Louisville homes, galvanized steel pipe rusts closed from the inside over decades and slowly strangles flow. This is the one case that can mean repiping a section, but it’s the last thing to suspect, not the first.
When it’s not a simple fix
A couple of signs mean it’s worth a call sooner than later:
- Pressure dropped suddenly and you see wet spots or hear running water That can be a hidden leak or a slab leak stealing pressure. Shut the water off and call, this one doesn’t wait.
- The whole neighborhood is low Sometimes it’s the city main or a water-department issue, not your house at all. A quick call to Louisville Water rules that out for free.
How we’d diagnose it
When we come out for low pressure, we start with a gauge on an outside spigot to read your actual incoming pressure, then check the PRV, the shutoffs, and the water heater before we ever talk about pipes. The goal is to find the one thing that’s actually throttling you and fix that, not to sell you a project you don’t need.
Common questions we get
Is low water pressure an emergency?
Usually not. If it’s one fixture or a gradual drop, it can wait for a normal appointment. The exception is a sudden house-wide drop paired with wet spots, a spike in your water bill, or the sound of running water, which can be a leak, and you should shut the water off and call right away.
Can hard water really cause low pressure?
Yes. Louisville’s water is hard, and over time the scale it leaves behind clogs aerators, showerheads, and valves, and it builds up inside older pipe. It’s the single most common reason a fixture slowly loses flow.
What’s the difference between low pressure and low flow?
Pressure is the force pushing the water; flow is how much comes out. A clogged aerator lowers flow at one fixture even when your pressure is fine. A bad PRV or a partly closed valve lowers pressure everywhere. We check both when we diagnose it.
Will a booster pump fix my low pressure?
Sometimes, but it’s rarely the first answer. If the real cause is a half-closed valve, a bad PRV, or a clogged line, a pump just masks it. We find the cause first; a pump is a last resort when your incoming pressure is genuinely too low.
The next questions to ask
Not sure if it’s a five-minute fix or something bigger?
Ask Goldie walks you through it in a couple of minutes and tells you what’s likely going on before anyone comes out. Try it at goldenplumbingky.com/instant-estimate/