Low Water Pressure in the House: Finding the Cause Room by Room
Pressure problems get diagnosed by geography. Where the pressure is bad tells you almost everything about why.
One fixture only
Start with the aerator — the little screen on the end of the faucet. Unscrew it, and you will usually find grit or mineral flakes. Rinse it, put it back, and see if flow returns.
If that does not do it, check the angle stops under the sink are fully open. If it is a shower, the cartridge or the head is the next suspect.
Hot water only
If cold runs fine everywhere but hot is weak, the problem is at or after the water heater. Scale in the outlet nipple, a partially closed valve on top of the tank, or sediment build-up are the usual causes.
Every fixture in the house
Now it is a whole-system problem, and there are four realistic causes.
1. The pressure regulator
Many homes have a pressure reducing valve near where the water enters. They fail gradually, over eight to twelve years, and the symptom is exactly this — everything a bit weak, everywhere, getting slowly worse. It is a straightforward replacement.
2. A leak on the supply line
Water escaping before it reaches the house shows up as lost pressure. Check for a soggy strip of yard between the meter and the building. Then run the meter test: shut everything off, watch the dial. Movement means a leak. Water line repair is the fix.
3. Old galvanized pipe
Galvanized steel corrodes from the inside. Over decades the internal diameter narrows until a three-quarter inch pipe is passing water like a straw. Nothing restores it — the pipe has to go. If your house still has galvanized supply lines and pressure keeps declining, repiping is what you are looking at.
4. The utility side
Occasionally it is genuinely not your problem. If neighbors have the same complaint, call the water district before you call us.
The test that saves you money
Before anyone quotes you anything, put a pressure gauge on an outside hose bib. Normal residential pressure runs 45 to 80 psi. Under 40 explains the complaint. Over 80 is a different problem — high pressure destroys water heaters and fixtures, and needs a regulator.
Gauges cost about ten dollars at any hardware store, and having a number changes the conversation.
When to call
If the whole house has weakened over months, get it looked at before the cause finds a more expensive way to announce itself. Call (833) 435-9778 for a same-day pressure diagnosis.