Low water pressure at one faucet or the whole house

Question 1: Is it one faucet or shower, or the whole house?

Run a couple of other taps, including one on another floor if you have one.

• Just one faucet or shower: go to question 2
• The whole house: go to question 3

Question 2: At that faucet, is the flow weak on hot, cold, or both?

Run full hot, then full cold, and compare.

• Hot only: Likely cause: a restriction on the hot supply
• Both hot and cold, or cold only: go to question 4

Question 3: Are both main shutoff valves fully open?

Many homes have one at the meter and one where the pipe enters the house. A ball valve is open when its handle lines up with the pipe.

• Not sure, or one was recently closed for work: Likely cause: a main shutoff that is not fully open
• Yes, both are fully open: go to question 5

Question 4: Have you taken off and cleaned the aerator (and the hose screen, on a pull-out faucet)?

The aerator is the screened cap at the tip of the spout. Most unscrew by hand.

• Not yet: Likely cause: a clogged aerator or hose screen
• Yes, and it is still weak: Likely cause: debris in the cartridge or a stuck diverter

Question 5: Did the pressure drop suddenly, or fade slowly over months or years?

• Suddenly: Likely cause: a failing pressure regulator
• Slowly over time: Likely cause: clogged or corroded pipes