Hot water still flowing with the unit off (bleed-down or cross-over)

What is going on

Water keeps flowing at fixtures after the hot supply is shut off. The cause is a faulty fixture, check valve, cross-over, or mixing valve.

Likely causes

• Faulty fixture diaphragm
• Faulty check valve in the plumbing or circulation return
• Cross-over in the plumbing
• Faulty mixing valve

Check in this order

1. Ask the customer to describe the problem.
2. Turn off the hot water ball valve on the Rinnai valve kit at the unit. Open a hot fixture and wait about two minutes for residual water to drain.
3. If water still flows at any rate, find and repair the faulty fixture, check valve or cross-over.
4. If there is a circulation loop, close the loop's shut-off valve in the return line. If flow stops, the loop is clear.
5. At each single-handle fixture, close the cold ball valve one at a time and watch flow. If flow stops, reopen the last valve closed. If flow restarts, that fixture has a bad diaphragm; replace the insert or add a hot-line check valve.
6. If the location has a mixing valve, isolate it and shut off its cold feed. If the water stays at temperature, the mixing valve is the problem.

More tankless water heater guides

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• Water leaking from pump housing