Quick Answer:
If the utility has shut off the main but your taps still have pressure, it usually comes from water trapped in your home’s plumbing or a pressurized device such as the water heater or an expansion tank. Start by relieving pressure inside the house (open the highest faucet), then check the house shutoff, water heater, and expansion tank before assuming anything else.
Why This Happens
- Water trapped in pipes will keep fixtures flowing for a short time after the supply is closed — especially if you have tanks or elevated storage like a water heater.
- An expansion tank or a pressurized well-style bladder can hold significant pressure even when the main supply is off.
- In some cases a curb stop or meter valve fails to fully close; this is a mechanical problem at or near the property line. If you suspect that, check the meter area — sometimes the issue is the curb stop won’t fully shut off water or the meter valve stuck open.
Step-by-Step What to Do
1. Confirm the city shutoff
- Double-check any notice from the water utility or call them to confirm the shutoff time and location. This avoids wasting time investigating while the city still has water on.
2. Relieve pressure inside the house — drain the highest faucet
- Open the highest faucet in the house (top-floor sink or shower). Opening a high point helps air enter upper piping and lets trapped water move out.
- After that, open a lowest faucet or a drain to let the water run out. Doing high first helps avoid siphoning and reduces trapped pockets of pressure.
3. Turn off the house main shutoff
- Locate and close the interior main shutoff valve to isolate your plumbing from any small amount of flow that might still come from outside or a failing curb stop.
- If the interior valve is already closed, try to confirm whether it actually seated fully. Valves can stick or leak internally.
4. Check the water heater and expansion tank
- Check the water heater: it stores hot water under pressure. If it was recently heated, it can force water into the lines. Turn off the heater’s power or gas before doing any work near it.
- Check the water heater expansion tank. Tap it lightly — a hollow/air sound at one end and a dull/solid sound at the water side is normal. If the tank is waterlogged it can keep system pressure even after supply is shut.
- If the expansion tank has a Schrader (air) valve, you can check its air pressure with a tire gauge. Compare pressure to the cold water pressure setting recommended for your system. If you’re not comfortable doing this, skip it and call a pro.
5. Look for other pressurized devices or loops
- Irrigation systems, boiler loops, or an automatic makeup valve on a water softener can maintain pressure. Isolate these systems by closing their individual valves if present.
6. Observe and document
- After draining and isolating, watch the pressure or flow. Note where water still appears and whether it runs down slowly (residual) or continuously (suggesting a valve is letting water through).
What Not to Do
- Do not assume illegal bypass — don’t jump to conclusions about someone intentionally bypassing the meter or curb stop without checking valves and devices first.
- Do not try to force or hammer a curb stop or meter components. Those are utility-owned in many places and forcing them can cause damage or legal issues.
- Do not open the water heater relief valve to drain the tank unless you know the proper procedure — it can spray scalding water and release pressure suddenly.
When to Call a Professional
- Call your water utility if you suspect the curb stop or meter isn’t shutting off — they own and service those parts in many areas.
- Call a licensed plumber if you can’t stop the flow, if pressure remains after you’ve isolated and drained the house, or if you find a pressurized device you don’t know how to safely handle.
- Call a plumber immediately if you find active leaks or flooded areas you cannot control.
Safety Notes
- Turn off electrical power to areas near standing water before touching anything electrical.
- When checking the water heater, turn off the gas or electric power first. Hot water and steam can cause severe burns.
- If you need to open or depressurize any pressurized tank, follow manufacturer instructions or hire a pro.
Common Homeowner Questions
- How long will fixtures stay pressurized?
Short time — usually minutes to an hour depending on how much water is stored in the system or heater. - Could the problem be the curb stop?
Yes. A stuck or partially closed curb stop can let water through; have the utility inspect it if other checks don’t explain the pressure. - Should I turn off the water heater?
Turn off the power or gas if you will be draining or working near it; otherwise only turn it off if you suspect it’s the source of pressure and you are prepared to manage the tank safely.
For situations where valves at the meter or curb are involved, consider checking resources about curb stop won’t fully shut off water and meter valve stuck open for more detail or to prepare questions before you call the utility or a plumber.