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One rad heats up slowly, so plumber restricts valves on all other rads - really?

We were in the middle of a chaotic remodel and some things slipped through the cracks.  We have a beautifully refinished (in hammered copper) Rococo radiator in our entry way.  I noticed that the steam supply line off the main to that rad was a smaller diameter than the rest and pointed that out to the plumber.  He confirmed and then did nothing about it.

When the heat comes on, all our other radiators heat fairly evenly together with the use of vari-valve vents.  I pointed out to our plumber that the entryway rad never had a chance to get hot before the heat shut off due to the other rads in the household doing their job.  I immediately suspected the smaller diameter supply line, which is now buried in a wall.  His solution was to drop the vent from the high position on the rad to the low position (does this do any good?), open up the vari-vent all the way on the entryway rad, and close down all the other radiator vents to 50% or so.

Will this make our furnace work a little harder (waste of oil) given the increase in resistance?  Is this the appropriate solution?  The entryway radiator now does have a chance to heat up. Any advice would be greatly appreciated!

p.s. I've also noticed that two of our upstairs radiators are pitched the wrong way and 100% of the condensation cannot return to the furnace.  We don't suffer from water bang, although we hear some loud single clangs once in a while.  These rads put out decent heat, should I correct the pitch?  The vent end is a good 1" below the valve/return end.


  • One Pipe System?

    Let's start out by making sure what type of steam system you have. Is it a one pipe system or a two pipe system? That means that the radiators either have one pipe or two pipes attached to them. Most steam systems are usually all the same type (radiators are all piped the same) though you can have a mixture of 1 pipe and 2 pipe radiators.

    Hall radiator - If this is a one pipe system, the single pipe attached to the radiator must be attached to the bottom of the radiator otherwise the condensate couldn't get out of the radiator. On a two pipe system the steam enters at the top of the radiator and the condensate exits the radiator at the bottom by the second pipe. It would sound as though the radiator was originally hooked up to a 2 pipe system.

    One pipe radiators-  On a one pipe system

    the valve (tap) on the pipe going into the radiator must always be

    fully open or fully closed. This is because the steam (a gas) uses the

    top section of the pipe to go into the radiator and the condensate

    (water) uses the bottom section of the pipe to leave the radiator. If

    you make the pipe opening smaller ( by partially closing the valve) the

    steam going in and the condensate coming out collide and cause water


    Also the radiator should slightly slope towards the end where the steam pipe is attached just enough to "encourage" the condensate to flow out of the radiator. Too much slope can cause problems. The upstairs radiators that are pitched the wrong way should be corrected. Use a bubble type carpenters level as with old houses you can't go by (looks) measurement. I have a radiator that looks like it slopes the wrong way which is pitched properly. It just in that corner of the room, the floor sags.

    Do you have good main venting? I would check this out as using varivents can be  is a "mickey mouse" fix for lack of or poor main venting. Good main venting is a must for economical operation.

    If you don't have them already you might want to get a couple of very good books on steam heating which are available on this website one is "We Got Steam Heat" and the other is "The Lost Art of Steam Heating"  Both are humorous, easy reading, packed full of facts and diagrams and written so the homeowner can understand them. In a few evenings you'll know a lot more about steam heating. You can get them individually or as a package. Here's a link to the package:


    - Rod
  • K Penniman
    K Penniman Member Posts: 53
    Sorry, I'm referring to the variable vents, not the valves...

    Sorry to sound like a newbie - I have one pipe steam. I've read We Got Steam Heat. I've insulated my mains, checked that they have vents, etc.  All my valves supply the rads are fully open.  Yes, I used a level to confirm the slope of the radiators. 

    I didn't mean to confuse valve (on/off) with vent.

    When I refer to moving the vent to the lower position, on my Rococo radiator, there are two locations where I could screw in my vent (I use Heat-Timer Varivalve Quick Vent shown here [url=http://www.simplyplumbing.com/heat-timer-925005-00.html]http://www.simplyplumbing.com/heat-timer-925005-00.html )

    The plumber moved the vent to the lower position, indicating that this would help the radiator heat more quickly. Then, he turned the Varivalves to half open on the rest of the rads around the house.  Previously, all the vents downstairs were left wide open and we put all the upstairs vents at 50% to keep it cooler in our bedrooms.  It worked well expect for the one problem rad in the entry way.  Does the fact that all our radiators except the problem rad are vented at 50% negatively effect the efficiency of my system?
  • Venting

    Hi-  Sorry for all the elementary info, it's just that it's always hard to know quite where to start.

    After reading your reply, the first thought that came to mind was since you have two vent positions why not try a second vari vent on the hall radiator?  Too much venting may cause water hammer problems but only experimentation will tell.

      I'm a great believer in timing when steam reaches the different parts of your system (main vents, radiator valves, each radiator completely hot etc.) as this gives you a basis for comparison when you make a change as to whether that change is actually beneficial.

    I also think I'd be more inclined to use TRVs to limit overheating than slowing  the radiator venting. I use TRVs in the upstairs rooms as it is easy to turn them up when you want the bedrooms warm and then turn them down for sleeping. The TRVs are also useful for shutting down parts of the house which saves on fuel.

    - Rod
  • RAF
    RAF Member Posts: 65
    Vent location

    The upper tap in your radiator is for venting if you have a hot water system.

    The lower tap is for steam .
  • K Penniman
    K Penniman Member Posts: 53
    Vent location

    I never new that about vent location!  Several of our rads have the Varivents at the higher point.  I'll move them as soon as I can!
  • Vent Location

    Steam being lighter than air, goes to the top of the radiator and fills the radiator from the top down.  Radiator vents close when the steam reaches them so being at the top of the radiator, that vent will close before all the air escapes.  If you have two vent holes, high and low and used a vent in each hole, the upper vent would help initially in allowing the air to vent faster. You could also use a tee and place two vents together on the same vent hole. There is a downside to fast venting (on radiators) as you are more likely to get water hammer and spitting especially when using Heat timer vents as they don't have a float.

    - Rod
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