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Can I add to existing hydronic radiant heat system?

We have an existing hydronic radiant heat system under the floor between joists in the crawl space, coming from hot water heater (through a temperature reduction mixer thing) to the kitchen. Works great. We would like to add to the system to go to the bathroom. Can we simply "splice the existing tubing" and run it to bathroom before returning to the hot water heater? or do we need to run a separate zone? What is the best way to add on? Do we need another whole system? Crawl space is 7' tall so no issue with working under there. We want to DIY because the quote we received from the plumber to add on, was equal to installing the original system. If splicing is okay, how do we work with the air that is in the line then? it just runs into the hot water tank and gets eliminated there? As you can tell, we're finding our way...

Re: Can I add to existing hydronic radiant heat system?

Your using your hot water heater as a hydronic boiler? If it's a boiler, then that makes perfect sense. Yes, it is entirely possible. Just run a separate zone out that way. But there are two things that you MUST check:

1) The BTU level of the boiler, which will decide it's capacity. One zone may not make much of a difference, but it's good to check.

2) The expansion tank. This is an enameled tank (should be green, grey red, but usually grey) that hangs from the return line with an air scoop (air eliminator) above it. Once again, the addition of a small zone does not make much difference, but the expansion tank will be rated for a specific number of gallons.

Also be sure to ensure that the zone valves/pumps are consistent. If you have zone valves, add a zone valve of the same make. Same goes for the circulator zone pumps. Good Luck!:)

Re: Can I add to existing hydronic radiant heat system?

There are systems with run off a residential water heater - not sure how powerful they'd be, but for "comfort" heating of a floor, it might be possible to add another zone. It depends on what your system was rated for to begin with.

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