Why are my cold taps running tepid after a water heater service?
Servicing a tankless water heater can disrupt the balance, leaving cold taps running tepid for minutes and sometimes causing scalding hot water to push through the cold side. This unexpected crossover makes it difficult to get normal cold water and leaves residents caught in disputes with building management over who is responsible for the plumbing repair costs.
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.
- 1Searching online for solutionsDid this help you?
- 2Turning off the hot water master valve for the whole bathroomDid this help you?
- 3Replacing the cold and hot check valves and cartridge behind the shower bodyDid this help you?
- 4Turning off the hot water supply valve, turning on the faucet, and then turning the valves back onDid this help you?
- 5Replacing the faucet cartridgeDid this help you?
- 6Replacing the faucet with a name brandDid 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.
“We had our (tankless) water heater serviced last week - since then, getting cold water from the taps takes much, much longer. The coldest water for a good three minutes or longer is tepid.”source ↗
“I have hot, often scalding hot, water coming out of both my bathroom sink and shower when I am only using the cold tap or have it set to the cold setting.”source ↗
“The largest issue here is my building management is saying that I am responsible for all the costs as this is an issue with my unit's plumbing and not an issue with the building's plumbing and therefore it is not the building's responsibility.”source ↗