Why does water pressure drop when another faucet turns on?
Water pressure can drop significantly or go to almost zero when multiple fixtures are used simultaneously, sometimes linked to recently installed equipment like a new water heater. This sudden restriction leaves households with conflicting pressure readings and forces them to wait ten minutes or more for the system to recover after closing the fixtures.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
Found another way around this?
Share your steps and trade-offs so fellow engineers don't have to reinvent the wheel. No account required.
Why does water pressure drop when another faucet turns on?
- 1adjusting the pressure settingDid this help you?
- 2taking the PRV apartDid this help you?
- 3cutting the shutoff valve off multiple timesDid this help you?
- 4waiting for system pressure to build up with all fixtures closedDid this help you?
- 5Getting multiple assessments from different plumbersDid this help you?
- 6Testing water pressure with a gauge on an exterior hose bibDid this help you?
- 7Replacing old corroded galvanized pipes with copper or PEXDid this help you?
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“when a 2nd water source is being used, the water pressure is dropping significantly.”source ↗
“I keep getting conflicting results when I check the pressure.”source ↗
“Now, if someone is showering and someone flushes a toilet, the pressure drops to almost zero on the Radon water system pressure gauge and wont build up until all fixtures are closed for 10+ minutes.”source ↗
“We didn't have this issue before the new water heater and I'm confused why installation of a new one would make a difference.”source ↗
“This plumber is telling me that I've got high water pressure, but I have episodes of low water pressure all the time. For example, I can't run the dishwasher and a shower at the same time.”source ↗
Where this came up
People with this problem also raised
- 8Low hot water pressure at only one faucet
- 4Why does water flow drop drastically with normal pressure?
- 3Why does my hot water stop when the sprinklers run?
- 12Why is there no water pressure after changing a faucet?
- 8Why is only one tap losing hot water?
- 4How to clear a slow draining shower without taking off the P-trap