Short answer: If every tap in the house is weak, look at the supply: a main shutoff valve that is not fully open, a failing pressure-reducing valve (PRV), corroded galvanized or old service pipes, a hidden leak, or a problem on the utility side. If it happened suddenly, ask your neighbors and call your water utility first.
Quick diagnosis
| What you notice | Most likely cause | What to check | Call a pro? |
|---|---|---|---|
| Sudden drop, neighbors too | Utility work or main break | Ask neighbors; check the utility’s outage page | Call the utility |
| Sudden drop, only your house | Main valve partly closed, PRV failure, leak | Check the main valve and the meter | Often |
| Weak for years, older home | Corroded galvanized or old service line | Ask when the pipes were replaced | Yes |
| Hot water only is weak | Water heater shutoff or sediment | Compare hot and cold | Sometimes |
| Weak only with a well | Well pump or pressure tank | Check the pressure gauge on the tank | Yes |
Check these first
- Ask a neighbor or check your water utility’s website for outages or main breaks.
- Make sure the main shutoff valve (where the line enters the house) is fully open.
- Find the pressure-reducing valve, usually a bell-shaped valve right after the main shutoff. Many homes have one; if it fails, pressure can drop or spike.
- Turn everything off and watch the water meter. If it still moves, you probably have a leak, which also lowers pressure.
Old pipes and the service line
Denver Water explains that low pressure in older homes is often reduced flow caused by mineral buildup narrowing old lead and galvanized service lines, and that the service line from the street is the property owner’s responsibility. The permanent fix is replacing the line, done by a licensed plumber or contractor.
Pressure-reducing valve (PRV)
A PRV keeps city pressure at a safe level for your home. When it wears out, pressure can drop or become erratic. Adjusting or replacing a PRV should be done with a gauge, and many homeowners hire a plumber for it.
Homes on a well
With a private well, whole-house low pressure usually points to the pressure switch, the pressure tank or the pump. A gauge on the tank shows the cut-in and cut-out pressures; a well contractor or plumber can diagnose it.
When to call a professional
- The meter moves with all water off (possible leak).
- Pressure dropped suddenly and the utility says there is no problem on their side.
- You have old galvanized or lead pipes.
- The PRV needs adjustment or replacement.
- A well system is losing pressure.
What it usually costs
Plumbers typically charge $45 to $150 per hour plus a call-out fee (HomeGuide, 2026). Replacing a service line or repiping is a major job; get written quotes.
Frequently asked questions
Why did my water pressure suddenly drop in the whole house?
Utility work, a main break, a partly closed main valve, a failing pressure-reducing valve or a leak are the most common causes.
Who is responsible for low water pressure?
The utility handles the water main and meter in most cities; the service line and plumbing on your side are usually the owner’s responsibility. Check your utility’s policy.
Related problems
- Low water pressure in one faucet or shower
- No hot water
- Pipes banging (water hammer)
- Toilet keeps running
Sources
- Denver Water: Low water pressure
- City of Phoenix Water Services: General service issues
- HomeGuide: Plumber cost per hour (2026)
This guide is general information, not a substitute for an inspection by a licensed professional. See our disclaimer.