Why Is My Water Pressure So Low All of a Sudden?

There's a difference between water pressure that's always been a little weak and water pressure that suddenly dropped overnight. The second one is usually more diagnosable, because something specific changed. Working through the possibilities in order, from the simplest to the most involved, will get you to an answer faster than guessing.

Step 1: Is It One Fixture or the Whole House?

This is the single most useful question you can ask yourself first. Turn on a few different faucets around the house, including one on a different floor if you have one, and see if the weak pressure is isolated or widespread.

If it's just one fixture, the cause is almost always local to that fixture:

• A clogged aerator screen at the tip of the faucet
• Mineral buildup inside a faucet cartridge
• A partially closed shutoff valve under that specific sink

If it's the whole house, look further up the chain.

Step 2: Check for a Partially Closed Main or Shutoff Valve

If you've had any recent plumbing work, a shutoff repair, or even just knocked into a valve handle while storing something nearby, check that your main shutoff and any water meter valve are fully open. A valve that's only opened partway can dramatically reduce pressure to the entire house without cutting it off completely.

Step 3: Check Your Pressure Regulator

Many homes, especially those on municipal water, have a pressure-reducing valve (PRV) installed where the main line enters the house. These regulators can fail over time, and when they do, they sometimes fail toward low output rather than high. If your home has one, it typically sits near the main shutoff and looks like a bell-shaped fitting with an adjustment screw on top. A failing PRV is a common cause of a sudden, whole-house pressure drop in older homes.

Step 4: Consider a Municipal Supply Issue

If your neighbors are also experiencing low pressure, or if you notice it coincides with nearby construction, a water main repair, or a boil-water notice, the issue may be entirely outside your home. A quick check with a neighbor or your local water utility's website can rule this in or out fast.

Step 5: Look for a Hidden Leak

A leak elsewhere in your plumbing system, whether in a wall, under a slab, or underground on the line running to your house, can rob pressure from the rest of your fixtures because water is escaping before it ever reaches your faucets. This is a less common cause but worth considering, especially if you've also noticed an unexplained jump in your water bill or the sound of running water when nothing is turned on.

A Simple Order of Operations

1. Determine if it's one fixture or the whole house
2. Clean the aerator if it's isolated
3. Check that all shutoff valves are fully open
4. Inspect the pressure regulator, if your home has one
5. Ask around about a possible municipal issue
6. Watch your water meter for movement with everything off, which points to a leak

When to Call for Backup

If you've ruled out a clogged aerator and confirmed your valves are open but pressure is still low across the house, the remaining causes, a failing regulator, a hidden leak, or a supply line problem, aren't things you want to diagnose by trial and error. ProFlow Plumbing has the pressure gauges and leak-detection tools to pinpoint exactly where pressure is being lost, rather than replacing parts one at a time and hoping something sticks.