Water leak from screw after flushing water heater
Flushing a tankless water heater for maintenance can cause a small water leak to develop around a housing screw or union. This usually happens because the screw acts as a penetration through the housing, forcing homeowners to try tightening the fittings themselves or risk calling a technician before the problem worsens.
What the numbers show
Counted from the threads quoted below. How we count
- This comes up 16.1× more often in r/Plumbing than across the site as a whole.
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.
- 1Tightening the union fittingsDid this help you?
- 2Calling a technicianDid this help you?
- 3Buy a rubber cap and a clamp from a big box store to plug the open disposal inlet.Did this help you?
- 4Hook the dishwasher hose back to the disposal and use a disposal waste kit.Did this help you?
- 5Shut the main water off firstDid this help you?
- 6Open the lowest faucet in the house to drain the linesDid this help you?
- 7Replace the rusted plug or capDid this help you?
- 8Remove the tee fitting entirely or put in a couplingDid this help you?
- 9calling for serviceDid 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.
“Unfortunately, they didn’t plug garbage disposal as you can see and I found that out the hard way with water all over the place when loading the dishwasher this morning.”source ↗
“I have a small leak coming from a screw.”source ↗
“this happened after I flushed the water heater last week.”source ↗
“If its on the union, tighten the union and pray. If its from the screw, its inside the cabinet and using the screw as a penetration through housing.”source ↗
“Thank you. I didn’t want to call a technician but I don’t want the problem to get bigger.”source ↗
“Happened right after a washing machine load has finished, does anyone know how to stop for now, and then how to fix? Uk in case that’s relevant”source ↗
“There is water slowly welling up from its top, which crawls down the side of the humidifier and falls to the floor.”source ↗
Where this came up
People with this problem also raised
- 2Why is a puddle forming from a pipe outside my house?
- 7Why is my dishwasher leaking from the back between the metal and plastic?
- 3Water dripping after changing a whole-house filter
- 15Why is water backing up into the sink when appliances drain?
- 10Why does my new smart toilet have a weak flush?
- 2Why do P-traps lose water when the ejector runs?