Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Replacing Hot Water Tank

06honda Member Posts: 15
edited January 2017 in Radiant Heating
I have a 1100 square foot bungalow on slab with infloor radiant heating. 2 zones, hot water is obtained from a 65 Gallon Hot water tank that runs off natural gas. Heating bills are pretty good, the highest month for the past 5 years here in southern Ontario was $135. My plan is to replace the 1999 hot water tank and have considered maybe going with a tankless hot water tank. Upfront cost is much more but my main questions are:

Q1: Will a tankless hot water tank work with my infloor radiant system?

Q2: Will the tankless hot water tank cycle frequently?


  • Ironman
    Ironman Member Posts: 6,895
    Don't do it; you'll regret it!

    Tankless water heaters are not designed, controlled or approved for space heating. The heat exchanger has an enormous amount head that will choke the flow produced by a hydronic circulator.

    Most manufacturers will only warranty them for 3 years or less if used for space heating.

    Use the right tool for the job: a boiler. It will be a lot more efficient than a tank water heater if done correctly.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • kcopp
    kcopp Member Posts: 3,997
    I would NOT use a tankless to run your system. Do you also use the water heater to get your domestic hot water?
  • 06honda
    06honda Member Posts: 15
    Yes there is just one hot water tank for both. I was not set on getting a tankless but wanted to explore if it was a good idea. I am willing to just replace the current hot water tank with a similar one no problems, way cheaper also. Just as a point the temp that my floor works at is 110 F.
  • Abracadabra
    Abracadabra Member Posts: 1,948
    Sorry.. but whenever I hear "I want a tankless hot water heater" I always think of this:

    The information may be presented in a silly way but the information is all true.
  • 06honda
    06honda Member Posts: 15
    I listened to it, great and true points. Good post.
  • kcopp
    kcopp Member Posts: 3,997
    You should really separate the Heating from the domestic hot water.
    A good Modulating boiler w an indirect water heater would be perfect. If space is an issue you could go the combi route. A bit of a trade off w the boiler being oversized but its better tha you have now.
    I personally like this unit.