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Smallest pex and floor track for a bathroom

my bathroom , and want to radiant heat the floor . The original Levitt radiant was the best and we all just plain miss it too much in there . Burning your feet on the hot spot while on the bowl was fantastic !

The full size will be 8' by 8' , but the functional heating area will be around 5' by 4' . What I need is the thinnest diameter pex and pregrooved flooring system made . I'm trying to avoid a speed bump from the hallway into the bathroom . I seem to have a walking problem after a few drinks too many , and don't want to take a header into the glass bath doors . And is there a preffered method to attach this type of grooved system to concrete ? Does the floor feel " spongy " when it's on top of concrete ?

I was also thinking of using small diameter pex right on the existing concrete and using some thin set ( is there such a thing as thick set ? ) , and tile right on top . Anyone try this ? I'm not too concerned about matching the size and length of pipe to the heatloss of the bathroom . It'll be on it's own zone , tempered down , and I mainly want it for the warm floor . Electric mats are not a viable option with our skyhigh rates .

Once again thank you for any help in advance .


  • Maine Ken
    Maine Ken Member Posts: 531

    5/16ths w/ 1/2" panels is the thinnest i've seen. Glued panels fell real solid. I don't know of a way to hold the pex in place going with a thin coat.

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  • bill_46
    bill_46 Member Posts: 6
    bath floor heat

    wow I like you plan, now how is this done?
  • Ron Schroeder_3
    Ron Schroeder_3 Member Posts: 254

    In the true Levitt tradition, 1/4" copper in the morter..........just kidding..........sort of.

  • bill_46
    bill_46 Member Posts: 6
    bath floor heat

    wow I like you plan, now how is this done? Good 1/4th is a start. Now don't put the copper under the first one foot in side the door. smaller bump.
  • Weezbo
    Weezbo Member Posts: 6,232
    5/16\" he pex.

    get some staples used out doors for wires nail it down..pour 5/8ths put the tile over it call it good. if you have two loops instead of one on the zone you can keep the water temps down and put more of the material in the floor for more even heating,and should some one drop a pitch fork in your floor you can turn one of theloops off and only use one loop.
  • Actually , that is not

    a bad idea at all . It certainly would be the thinnest way to go . I could make an all flare manifold right near the boiler . I would guess 2 loops of 60 foot 1/4 inch would do the trick . So , how exactly do I throttle down a 007 to push water through 2 loops of oil line ? Thanks alot Ron .
  • todd s
    todd s Member Posts: 212
    copper in concrete

    Why not use coated oil line? I don't know if you want to try it but it would seem that it would hold its shape pretty good.
  • I just remembered

    I have a Hilti gun somewhere around here . As you can gather , I've never set a tile in my life . Whatever I decide to use to hold the tubing down with will stick that much more off the ground . The copper idea makes more and more sense - it's smaller diameter than pex and it will hold the shape you want it to , more or less . I might just try spreading out some thin set , laying the 1/4 inch copper in it , then the tile . Sonds kinda like the messy way to do it , huh ? Thanks Weezy .
  • How's the heat transfer

    through the coating ? You think bare copper could have a reaction with thin set ? I wouldn't be too bothered about it though . The bathroom is small , replacing the tile ain't gonna be too bad , and I have probably 5 or 6 decades to start worrying . We started a baseboard job today . The customer is an original Levitt homeowner , bought the house brand new for $7000 in 1950 . The radiant finally gave out last week . Not too bad for the 1st mass produced slab heated homes . Thanks alot Todd .
  • todd s
    todd s Member Posts: 212
    coated lines

    I don't know how much the coating would act as an insulator but I always remember how much greater the transfer of heat is through copper as compared to pex. I wonder if anyone here has done this before.
  • Ron Schroeder_2
    Ron Schroeder_2 Member Posts: 176

    I was thinking of probably at least 4 loops less than 20 feet long each.

    Is this zone going to have it's own circ? Is the rest of the house going to stay radiant floor or will you have to have two watter supply temps?

  • hr
    hr Member Posts: 6,106
    You might consider an electric

    mat or cable system for that size room. They come in VERY small diameters, directly install in the thinset, and could be operated seperatly from the hw system in shoulder seasons. Setback controls re easily installed also.

    If not, I have done some jobs with 1/4" soft copper coils. Think I would go 6" on center and 50 foot or less loop length. Or two loops of whatever length fit into an 8X8 room.

    hot rod

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  • Dale
    Dale Member Posts: 1,317
    The cobblers children will have shoes

    The most prolific installer on the wall has time for his own bathroom remodel! I'm a little sheepish as I paid a door guy for a big new slider install, at least I did the inside trim.
    Is there a place you can put a little manifold in the bath area, like behind the side of the tub? That way you could run larger pex to the bath and go from there to the smaller size if you wished. Also, Would be nice to get some fin tube behind the tub too if it's one of the old cast iron ones. Would your wife allow a concrete saw into the house? A 1/2 in slot isn't too bad and would chisel pretty easy to a 3/8 pex. Sure some heat would go down but alot wouldn't.
  • The bathroom

    will be on a separate zone . The 1st floor zone and the upstairs will still be baseboard heat . I just bought a Weil Plus 30 indirect also , so repiping the boiler will be a must anyway . I can get my hands on a Honeywell outdoor reset control , but I have no clue how to work it into a system like this . Do you know of a premade zone valve package for separate temp zones ? The boiler and indirect are under the stairs and room is tight . Thanks Ron .
  • I was thinking of the electric mat

    and having a DEEP setback on the thermostat . How much power do these mats draw ? From what I understand , next to NYC , we have the highest electric rates in the country . And I hate adding anything to that bill ! But ... if the power consumption is near the same as running a circ for the floor zone , the electric mat becomes feasible , don't it ? I just used the Slant Fin heatloss program , I have about a 1500 BTU load in there .

    If I go hot water for the radiant , I was going to buy a few rolls of 1/4 by 60' oil line , 2 loops minimum . Looking at the room , 6 inches on center and I'll have alot left over . Maybe enough to heat under the tub too . Here's a question I forgot all about - can I use some type of dimmer switch to throttle down the power , and the flow through a 007 ? Will it put stress on the motor ? Reason I'm asking is I can get my hands on dozens of used 007s and I have a few dimmer switches around here - frugal is my middle name . Thank you very much Hot Rod for your advice .
  • Aw shucks

    Thanks Dale . Actually I'm gonna do the remodel in steps . Starting next week . 8 feet of the bathroom is outside wall , and the whole sill plate is behind the bath tub and is rotted out . I'm gonna try to replace that from the inside . Then I have to rechop the floor and move the toilet drain . I'm thinking the radiant will be next to last on the list , just in time for summer .

    The boiler room is adjacent to the bath , so building a manifold near the boiler is not a problem . We're replacing the old steel tub with a large shower , probably an exotic type of plastic . The 1/2 inch slot is a good idea , I wish there was some sort of concrete router I could use . The original heat was radiant , buried right between the sand and cement about 3 inches below grade . These homes were amazingly efficient - my manager told me the average oil consumption with radiant and the old GE or York boilers was around 600 gallons a year . Thanks for the ideas Dale .
  • Jed_2
    Jed_2 Member Posts: 781
    Is the slab that cold, Ron,

    that you need floor heat. I'm sure you must have thought about this, but what about a nice towel warmer?

  • sebast
    sebast Member Posts: 30

    Check out Heat Weave by Watts radiant, elec. floor mats cut and ordered to size. Or use Watts water pex, you can get it 1/4" dia. Then again you said Weil McLain ultra (no evoh protector on water pex and a aluminum boiler???), but thats another contradictory issue. www.wattsradiant.com
  • Yes it is

    that cold . Even colder - knowing how it used to feel like before the radiant failed . The whole bathroom is being gutted , I might as well put in all the creature comforts .
  • hr
    hr Member Posts: 6,106
    If you convert BTUs to watts

    I come up with about 400 watts of electric cable or mat to equal 1500 BTU/hr. So yes more power consumption than a small circ at @ 80 watts.

    Do the math based on your KW cost to get an operating cost per hour. Keep in mind it would not need to run 24/7.

    But you do have to fire the boiler for the hw heat and with an Ultra you may be running two circs (p/s piping) to get that 1500 BTU to the room.

    If HW is your final choice think I woul get some coated 1/4" copper. Be easier to attach and keep flat than pex tube.

    A better conductor, also :)

    Don't know if a regular rheostat could vary a pumps speed. Good question for the pump manufacture.

    hot rod

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  • Ron Schroeder_3
    Ron Schroeder_3 Member Posts: 254

    > Here's a

    > question I forgot all about - can I use some type

    > of dimmer switch to throttle down the power , and

    > the flow through a 007 ? Will it put stress on

    > the motor ? Reason I'm asking is I can get my

    > hands on dozens of used 007s and I have a few

    > dimmer switches around here - frugal is my middle

    > name .

    Dimmer switch to control the pump? Good question. I wonder how the injection pump controls vary the pump speed? I know that some of them work with standard wet rotor circs.

    Personally I like to use El-Sid or Laing DC pumps for variable speed.

    P & M Magazine had a good article on adding a small radiant zone to a baseboard system. I will try to look it up but it might take until monday before I have a chance.

    EDIT: Found it.......


  • jerry scharf_2
    jerry scharf_2 Member Posts: 414
    I wouldn't go with a dimmer

    I'm pretty sure the VS pumps that take s analog input mostly use triacs to control. The triac shuts off the power for part of the sine wave, which is a bunch different than dropping the overall voltage like a variable transformer does. Dropping the voltage can shorten the life of the pumps.

    The injection controls are different. They want an exact speed and so they synthesize a sine wave at the frequency relative to the speed they want it to turn. This is called a variable frequency drive.

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