Using a tankless water heater for radiant floor heat
Tankless water heaters used for radiant heat systems frequently suffer from black magnetic debris choking the inline filter and face skepticism from professionals who insist on boilers instead. This leaves homeowners struggling to select the right replacement setup, manage magnetite buildup, and handle simultaneous household hot water demands without running out.
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.
- 1Installing a magnetic filter to catch debrisDid this help you?
- 2Switching to a traditional cast iron boilerDid this help you?
- 3Considering various replacement options such as tankless models, power vented tanks, or heat pump unitsDid this help you?
- 4Evaluating whether to install a recirculation system for instant hot waterDid 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 have a radiant heat system that is run off a tankless hot water heater. A lot of people scuff at this and tell me I need a boiler.”source ↗
“There was maginite (black magnetic bits, I butchered the spelling) building up and choking the system, specifically the water heaters inline filter.”source ↗
“Can anyone help me select an alternative that would be appropriate for this application?”source ↗
“Hi everyone, my house has suddenly needed a bunch of work and I’m getting a bit overwhelmed by all the decisions I’ve had to make.”source ↗
“The tank is on its last legs and needed to be replaced anyway so I am going to put in one of the above options unless I’m missing an option.”source ↗
“We are already running out of water after about the third shower in the summer. The kids are young so I imagine it becoming a bigger problem as they get older plus we have winters”source ↗
Where this came up
People with this problem also raised
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