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Dip Tube Crazy Idea??

swellman
swellman Member Posts: 31
in Radiant Heating
We are replacing a radiator in our bathroom because the original one is too small = brrrrrr. 

There is some question about how we could run the lines to hide them best and whether a dip tube could be used to help. Keep reading if that sounds crazy (or not). 

The supply and return lines come in from the ceiling. We are going to mount the radiator above a toilet in the bathroom and sit it on an angle iron on the wall (the wall is brick behind). We currently understand it is best to supply the hot water to the bottom and have the return exit at the top. We are planning a bleed valve at the top of the radiator as well. 

We don’t love the idea(/aesthetic) of running the supply pipe all the way down the side of the radiator (about 44” plus the span to the ceiling). My contractor thus had the idea of using a ‘dip tube’ like those used on hot water heaters. Basically have the supply enter at the top of the radiator but run down the dip tube to the bottom of the rad. This gives me pause for a few reasons:

(1) Problems with getting air trapped around the dip tube (or because of the dip tube)? 
(2) Lifetime of the dip tube?
(3) Some other issue I haven’t thought of because it’s not conventional. 

Is this a crazy idea or a crazy brilliant idea if I did want to avoid running the pipe externally along the rad?
Can the bleed valve be positioned in such a way that a dip tube idea would work?? 

Thanks everyone. You guys are always the best on this forum. 

Comments

  • STEVEusaPA
    STEVEusaPA Member Posts: 6,506
    Are you sure you have enough flow going to the rad? And the right supply water temp? Proper pressure? Properly bled?
    Maybe the shut off is partially closed or there is a restriction.
    I couldn’t even follow the dip tube idea. Sounds like a waste of time.
    Maybe you can do some tightening up of the envelope.
    steve
  • Jamie Hall
    Jamie Hall Member Posts: 23,275
    Indeed, before I replaced the radiator I'd make sure that it is getting the flow and water temperature it needs. It might not be.

    I presume that your preference is to not have a pipe running down the side of the radiator. OK. But... how do you propose to get the return flow out? While it is conventional to have the hot water come in the bottom and the return water out the top or out the bottom on the opposite end, the hot can come in the top without much loss -- but the return has to come out somewhere.

    If the radiator has a large enough opening at the top, I can envision a custom fabricated and brazed or welded special bushing which allowed for a dip tube for the inlet and a return. But I've never actually seen such a critter in you local friendly plumbing and heating supply store, and it would have to have some sort of seal (compression, maybe) to allow the dip tube to be inserted, the bushing fitted over it and then threaded into place, and the seal tightened down... not a simple contraption.

    The air vent can and should be at the top of the radiator at the opposite end to the inlet anyway... that wouldn't change.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Ironman
    Ironman Member Posts: 7,375
    Your contractor apparently doesn’t understand how a radiator works. You can feed it from the top and return it from the bottom. There are thousands of them that were piped that way and have been working fine for 100 years.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
    mattmia2
  • swellman
    swellman Member Posts: 31
    Thanks for the comments! We are fairly certain the radiator is not to size... different contractors have identified that to be the case. We have had the line supplying it upsized previously to try and help but it didn’t improve things too much. It’s also currently a steel radiator and it heats up hot that I think the temperature to it is sufficient. It unfortunately just seems to lose heat too quickly compared to the other radiators on the loop it shares because they are all cast iron, besides the fact that the only steel one is in the coldest room of them all. 

    If we were to pipe in the top and back out the top... Will the bottom of the radiator actually heat up? It’s a wall mount style radiator that in our case we need to turn 90 degrees so that we can fit it on the only exposed wall of the room. (See scribble below of original configuration to help clarify). 



    We had planned on plugging one of the existing holes and drilling a new hole on the opposite side for the return to have supply come in the bottom, heat rise up and go out the return which would still be top side (and it would keep the bleed valve at the top of the unit). See Scribble number 2. 



    Does that trigger any more thoughts? Maybe you will all just tell me no problem mounting sideways with both at the top still and that would be win win :) Or is a configuration like option 2 a lot better and I should suck up the pipe down the side? 
  • Ironman
    Ironman Member Posts: 7,375
    What’s the brand of radiator? How about some pics?
    If it’s a standard panel rad, then no, you can’t rotate it 90* since that would prevent convection through it.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
    JohnNY
  • dopey27177
    dopey27177 Member Posts: 887
    You stated your problem clearly. The radiator is steel and it cools quicker than the other cast iron radiators.

    When you try to reinvent the wheel make sure the wheel is round.

    Jake
    Steam: The Perfect Fluid for Heating and Some of the Problems
    by Jacob (Jake) Myron
    IronmanCanuckerJohnNY
  • ChrisJ
    ChrisJ Member Posts: 15,667
    dopey27177 said:

    You stated your problem clearly. The radiator is steel and it cools quicker than the other cast iron radiators.

    When you try to reinvent the wheel make sure the wheel is round.

    Jake






    That and, what is the point in running a pipe all the way to the top of a radiator, to then run it back down to the bottom via a pipe on the inside!? Why not just connect it at the bottom, if that's the line of thought.

    Also......as others have said, plenty of radiators are piped at the top with zero problems heating.

    But in a home with all cast iron radiators, the last thing you want is a light weight steel radiator or length of baseboard in one or 2 rooms. It's never going to work right. The cast iron radiators have a much larger flywheel effect.

    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
    Ironman
  • mattmia2
    mattmia2 Member Posts: 9,630
    Danfoss makes a valve with a lance to feed it through one tapping. the honeywell unique valve worked similarly.
  • Jamie Hall
    Jamie Hall Member Posts: 23,275
    mattmia2 said:

    Danfoss makes a valve with a lance to feed it through one tapping. the honeywell unique valve worked similarly.

    Yes -- but the return has to come off another tapping for the Danfoss, I believe. Possibly not -- and in any event, it's straight...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,002
    We've used single entry valves before. You still have two pipes, but it would look neater.



    Air won't be a problem with a down feed system, at least not at the radiator itself. You may need a vent where your pipes turn horizontal above.
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab

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