Why is my combi boiler so unreliable?
Combi boilers frequently suffer from inconsistent hot water, heating failures, and persistent operational issues that defy diagnosis. These breakdowns leave homeowners at their wits' end and often drive them to regret ditching older, reliable systems for a combi setup.
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 is my combi boiler so unreliable?
- 1Separating the water heater from the boilerDid this help you?
- 2Using a gas boiler with an indirect water heaterDid this help you?
- 3Replacing with a natural draft water heaterDid this help you?
- 4Jumping out the pressure switch on NO and NC to make the boiler run fineDid 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.
“I went the combi route 6 years ago to replace my old reliable 30 year old cast iron oil boiler and regret it. Inconsistent hot water and other issues on the heating side and I'm replacing that with a cast iron gas boiler on Tuesday.”source ↗
Where this came up
People with this problem also raised
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- 3Navien boiler has no hot water and shows T High error
- 3Why is water pooling inside my furnace?
- 2Why is my gas furnace getting so hot?
- 27Water heater going hot and cold with weird refill noises