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Radiator to radiant floor in a 2nd story bathroom.

mjp82mjp82 Member Posts: 23
I'm going to a restore on my master bathroom wich will entail ripping out the last owners hackjob shower and the homes orginal wood floors to reseal everything and tile over. In the process I'd like to see about removing the radiator (gas hot water) and replacing it with under floor hot water. I've got a few questions about doing this.

First, its a fairly large bathroom with a fairly large radaitor, but removing it would allow me to include a clawfoot tub to the room ( Happy wife Happy...) what I need to know it how would I calculate the size of the radiator to the floor space to see if this is even possible.

Second, can some one point me in the direction of a good how to or technical manual on the subject. I'm by no means a professional plumber but I did pretty well ( with the help of this sit and a few books,) but I like clear instructions, that explain why I'm doing something so I can better adapt the technique to my situation.

Third, any suggestions- things to look for, common mistakes people make etc would be great.

some things that may help ( I've got very a tall ceiling in the room and I'll be ripping the floor to the studs so the extra height wont be an issue.

my boiler is at 120deg. ( it came this and I've been told this is too low by some and right on by others but as it stands my gas bill is pretty good.)

Its a older home, 1925 that I think was set up as hot water from the beginning ( from the look of the pipes I dont think it was single pipe steam converted.)


  • IronmanIronman Member Posts: 6,176
    The simple answer is don't attempt it. No matter what size emitter you install, it won't be high mass like the old cast iron rad. You'll end up with a cold bath that has a claw foot tub ( unhappy wife...unhappy).
    That system was designed to operate with all high mass emitters in equal Librium. A low mass floor would be out of balance with the rest of the system.
    Then there's the issue of creating another water temp zone which would be a micro zone that would create short cycling of the boiler.
    If you really want radiant in there, look at electric radiant.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • mjp82mjp82 Member Posts: 23
    Now only two follow up questions, because I don't want to use only electric in that room, and the location of the radiator now prevents me from putting in a seperate tub from the shower stall.

    Can I relocate the radaitor by running iron pipe under the floor in a 90 from the wall its on currently across the room to the parrell wall? I've only worked with steam in the past and I know that would be a big no no, but I'm not sure how pitch and the number of elbows effects hot water.

    Second question if relocating the radiator its ok, is there any issue running the electric with the heat pipes directly under it ( I doubt it but my luck I'd install all this and it turns out that the warm pipes effect something.)

    Thanks for the feedback.
  • IronmanIronman Member Posts: 6,176
    I don't see any problems relocating the rad as long as you maintain the line sizes and keep a little slope on the pipes.

    I don't understand your second question. Are you asking if it's OK to run the rad pipes below the electric radiant? If so, yes, but completely below the floor, not imbedded in it.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • mjp82mjp82 Member Posts: 23
    I'd be running the hot water pipes between the floor joyces ( I'm sure thats misspelled) between the first floor ceiling the bathroom sub floor.

    So where the pipes come out of the floor down to the radiator I'd cut them below the floor and thred them then attach a 90 then a run between the joyces and another 90 to come up through the floor on the other side of the room. Then install the subfloor ontop of the joyces ( like you would normally.) So it would be in the cavity between 1st level ceiling and 2nd level floor.
  • GordyGordy Member Posts: 9,530
    I think the radiator with the electric radiant to just warm the floor would be very elegant indeed. The cost to operate the floor would not be bad as it will not need to heat the space. Elegant =happy wifey!

  • icesailoricesailor Member Posts: 7,265
    If this "older" home has this bathroom on the second floor, you have no idea what you will be in for. Most professional plumbers develop anxiety attacks when confronted by the dreams of homeowners who want to modify an existing second floor bathroom. If the house was 1925 vintage, and the bathroom was existing, there was a claw foot tub there before. The previous hack job done by others, probably includes connecting a shower with a 2" drain to a 1 1/2" lead waste that was connected to a illegal drum trap. The shower base might turn into a mini foot bath when taking a shower. Claw foot tubs aren't much better. If your happy wife is tall, she won't be happy using a claw foot tub. They fit in a 5' space, but so does a 5' recessed tub. But there's more room in one. Go to a Kohler bath showroom and sit in a Kohler Claw Foot Tub. The reason the sides are so high is so that there is enough water in the tub to cover women's chests and not be left out of the nice warm water.

    Post some photos of this bathroom. Especially the shower. I'm always up for entertainment.

    As far as the radiant, I doubt seriously that you have enough floor space to heat the bathroom with radiant pipes in the floor. But that electric mat works really well in your situations. When the budget goes South, you'll be looking for other things.

    I'm not trying to discourage you, just pointing out the pitfalls of trying to do something that in conception, seems easy. From someone who has to try and make something that seems easy to you, look easy on my part.

    It never is.
  • mjp82mjp82 Member Posts: 23
    Not too worried about the plumbing end of the bathroom, its a converted bedroom done in the last 8 years with everything run through a bulkhead in the kitchen below. The homes plumbing was redone by the prior owners as well (professionally but with garbage fixtures.)

    It sounds like the electric mat and moving the radiator across the room to fit the tub might be the way to go.

    Aa far as the tub it self any suggestions on getting an orginal tub and having the porcelain re done vs buying new?
  • SWEISWEI Member Posts: 7,356
    Ironman said:

    That system was designed to operate with all high mass emitters in equal Librium.

    Are you suggesting we add benzodiazepines to our boiler water? ;)
  • IronmanIronman Member Posts: 6,176
    SWEI said:

    Ironman said:

    That system was designed to operate with all high mass emitters in equal Librium.

    Are you suggesting we add benzodiazepines to our boiler water? ;)
    Isn't spellcheck wonderful? :blush:
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.

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