Click here to Find a Contractor in your area.
In fairness to all, we don't discuss pricing on the Wall. Thanks for your cooperation.
Need to contact us? Visit

Am I venting my mains too fast?

PeteysPeteys Member Posts: 62
I have a 5 foot, 2 inch main that has a gorton 2 and 50 foot 2 inch main that has 3 gorton 2s. The 5 foot branch heats the radiators in like 5 minutes while the 50 foot branch takes up to a half hour. Judy wondering if I should reduce the main venting on the 5 foot branch with a gorton 1 to even things out. Thoughts?


  • Jamie HallJamie Hall Member Posts: 6,659
    I've been heard to say

    that you can't vent a main too fast...  although a #2 on a five foot main is, perhaps, overkill.  However, that by itself does not explain half an hour for a 50 foot branch.  5 to 10 minutes, max, would be more like it.  The venting you have should be adequate -- which leads me to wonder if there might be something else wrong with that branch.

    Is it insulated?  Does it pitch properly and consistently for its full length?  Are there any restrictions (such as a valve, or a place where it gets smaller then larger) on it?

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-McClain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • ChrisJChrisJ Member Posts: 8,599
    edited April 2014
    Vents and size

    What radiator vents are you using and how does your boiler size compare to the connected radiation?

    My guess right now would be to slow up the main venting and radiator venting on the short main. It sounds like those are stealing your steam. One thing to keep in mind, the radiators on that short main no matter what will always have less resistance than the others. The further you are from the boiler the more pressure drop you have at the radiator. This means the vents on the radiators of the short main will always need slower vents to bring them into balance.

    I have the same problem with my system.
    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

    Steam system pictures
    Central air project pictures
  • nicholas bonham-carternicholas bonham-carter Member Posts: 6,535
    Slow rads

    I would think that 5 foot section should get steam to the rads more quickly than 5 minutes, so how is the piping on the boiler? Is the boiler undersized? Do you see much pressure on the gauge (at least 2 ounces)? Pictures would help.

    If you turn off the rads on the 5 ft line, will the steam get to the end of the 50 ft line more quickly? --NBC
  • PeteysPeteys Member Posts: 62

    All radiators have hoffman 40s. Mains are insulated but probably not pitched optimally on the long branch. I hear some swishing. No valves and same 2 inch for the full length. It takes 15 minutes to start getting steam to the farthest radiator on the 3rd floor of that branch when I disconnect it from the radiator valve.

    Boiler is oversized. Piping on boiler was redone properly with a dropped header. Tending to think its a pitch problem on longer branch but even if I fix that I believe the shorter main will produce steam to those radiators in a much shorter time, that's what I was thinking maybe reducing main venting on that line.
  • ChrisJChrisJ Member Posts: 8,599

    You'll get many opinions on this but my opinion is the Hoffman 40 is too slow for most uses. I have two Gorton #4s which I think are comparable. The rest are #5s, #6s and even two #Cs.

    I would increase your radiator venting greatly especially with an oversized boiler. Keep the 40s on the short main and beef up venting on the other radiators. An easy experiment is remove one of the vents on a hard to heat radiator and see how fast it heats.
    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

    Steam system pictures
    Central air project pictures
  • SnowmeltSnowmelt Member Posts: 750
    Very interesting

    I would think a few pics are worth a thousands words we need pictures, sooner or later my steam boiler is going to pop and I am going to switch it to gas but after the oil boiler poops out.

    It's a 1982 install
  • FredFred Member Posts: 5,221
    edited April 2014
    Something other than main venting

    There is something else going on other than the venting on the short run. Given it is only a few feet long, two gorton #2 is overkill but all that means is they should get hot and close pretty quickly pushing the steam up the radiator runs and back into the longer main (path of least resistance). With the 3 Gorton #2's on that run, the main should get hot in less than 5 minutes and start pushing steam to the radiator runs. I assume you have the Gortons on an antler of some type. Can you hear them venting? Is that antler made up of 3/4 inch pipe?  Is it possible that antler is somehow blocked or plugged? Do you have those vents at the end of the main where it becomes a return? You indicate you hear some swishing on the longer run. Is there banging as well? It is possible that there is enough water being retained along that run that the main can't reach temp for an extended period of time, steam condenses at that point and exacerbates the water problem. How often do you have to add water to the boiler? Do you see any steam clouds going out the chimney or hear any hissing at the boiler that might indicate you have a leak and are not building enough pressure to push the steam down the mains?
  • PeteysPeteys Member Posts: 62

    I have a maid mist c that I'm going to try on that run. What do you think?

    Gortons are on a 3/4 antler on that run and they are venting. They are 12 " before the end of main before dropping to dry return. This is one pipe parallel flow. And yes there is some banging so I know I need to straighten out that run. Don't think I have a leak in boiler but it does feed at times. Could this be because water is condensing where it is not pitched properly? And if it were pitched properly, wouldn't the steam arrive first on the shortest run anyway?

    Have a vaporstat set at 4 -12 oz.
  • FredFred Member Posts: 5,221
    I wouldn't use a Maid-o-Mist on a main

    If you want to reduce the venting on that short run, you could put a Hoffman #75 on that main but I wouldn't use a Maid-o-mist on the main. Given how short that run is, it is likely always going to heat first but that really isn't the issue. It needs a vent on it and when that vent get hot, be it Gorton, Hoffman Maid-o-mist or whatever, it is going to close and essentially be dependant on the radiator vents to finish the job venting the radiator risers. The real issue is why does it take so long to heat the long run. 50 feet is not an unusually long run and it should heat fairly quickly. The problem is most likely the water setting in that longer main. That water keeps the main cooler than it would be if it were dry and the steam is hitting that pool of water and condensing, probably until it gets that pool of water boiling and then it begins to move along the main to its destination.
  • nicholas bonham-carternicholas bonham-carter Member Posts: 6,535
    The other question is....

    Why is the short run so slow?

    Five feet with a Gorton 2 at the end should give you almost instantaneous steam arrival.

    Let's see the pictures of your boiler steam supply piping, where the problem may originate.

    The mains should be vented at maximum capacity, plus one vent. You can never over vent.

    If the boiler is very undersized, then that is another problem, and cannot be compensated for with inadequate venting, here and there.--NBC
  • ChrisJChrisJ Member Posts: 8,599

    A better question would be what exactly is the op timing?

    From the start of the burner until getting steam to the radiators?

    From start of producing steam until completely filling the radiators?

    Something tells me we are misunderstanding what exactly happens in 5 minutes on the short main.
    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

    Steam system pictures
    Central air project pictures
  • PeteysPeteys Member Posts: 62
    edited April 2014

    Sorry for confusion, was wondering on thoughts of using maid o mist c on farthest radiators on hard to heat long branch. Not on main on short branch.

    Guess I will try and fix main piping level on the 50 foot branch first and see what that does. Think you're right Fred. Too much condensing going on there.

    What about a gorton 1 on the shorter line instead of the gorton 2? I have one of those lying around. Would that slow things down?

    The short main gets hot immediately. Takes a short time to reach 3rd floor radiators. On that line.

    My big question is if both mains are fine after pitch correction on the longer branch won't there still be a difference in timing that should be corrected with either bigger radiator vents on the longer line or a smaller main vent on the shorter one?

    Any recommendations on what size radiator vents I should try on the long line to even things out?

    And could there be any adverse effects of reducing main venting on the shorter main? Spitting radiators, etc?
  • ChrisJChrisJ Member Posts: 8,599
    edited April 2014

    The shorter main may always get hot faster. A few had recommended I completely remove and plug the main vent on my short main. I originally had a Hoffman 4A on it and three Gorton #1s on my long main. Over time I learned I could use a single Gorton 1 on the short main with five #1s on the long main.

    If your short main comes off of the header before the long one, as mine does, you will find it difficult to slow the steam up.

    As I said previously in my opinion Hoffman 40s are slow, especially if on a 2nd or 3rd floor.

    Have a look at my venting map, it may give you some ideas. This was all done to get steam to my radiators equally and as fast as possible with as little pressure as possible. I currently have my system setup to shut down at 3 ounces so I never see more than that. Typically I see 1 ounce or less during normal operation.
    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

    Steam system pictures
    Central air project pictures
  • FredFred Member Posts: 5,221
    Yes to your question

    The answer to your question is "yes" the shorter main will probably always get hot faster than the long main and that's OK. You can certainly use a Gorton #1 on the short main. That should be adequate. The issue for you should not be which main gets hot faster but rather how to balance the radiators after you get the water out of the long run. When that is taken care of, you want to balance the radiators so that each room is heated evenly and that will probably mean putting different size vents on the radiators (smaller vents on those that heat too fast and larger ones on those that are slower to heat). Keep us posted on how you make out.
  • PeteysPeteys Member Posts: 62

    Thanks guys. Great advice. I will keep you posted.
  • Dave in QCADave in QCA Member Posts: 1,660
    Expected Operation

    With the combination of Main and Radiator vents that you have on your system, One would expect the steam to reach the end of the short main quickly, at which time it will close. Steam will continue flowing down the long main and will actually speed up when the short main is heated. Before the steam gets to the end of the long main, flow into the radiators should be minimal. After the steam has reached the end of the long main, those vents will close, causing a slight increase in pressure, at which time flow into the radiators should be begin. For the most part, the flow into the radiators would be expected to be fairly even. THIS is what would be expected, bit obviously, its NOT what you're experiencing.

    You indicate that you hear swishing in the long main. That is an indication of a huge problem. Water in the main will prevent steam from passing and when it does whoosh through, much of the steam will be condensed by the water. It would be similar to having a gate valve in the pipe and having is mostly closed. The system just cannot work correctly with water in that main.

    You indicate that the boiler is over-sized, yet you do not mention that it short cycles. Does it? I am also unclear in your description of 5 minutes for the short main and 30 minutes for the long one. Is that the amount of time it takes for the steam to get to the end of the main, or the time it takes for the radiators to be fully hot?

    You probably should also check the firing rate of the boiler. Many times, for various reasons, they do not fire at the rate on the rating plate. Make sure everything else that burns gas in your house is NOT running, operate the boiler, and count the usage in a minute by watching the needle on the meter that turns the fastest. The dial will tell you how many cubic feet of gas pass per revolution.

    Also, I'm wondering how often your boiler cycles. Once per hour? More often? Less often? When the boiler starts a new cycle, how hot is that long main? Do you have a way to measure its temperature? Or, perhaps the air coming out of the main?

    Reason being, while Gorton #2 main vents are incredibly fast when they're cold, the begin to close in the 130-140 range. If the air coming through them is 150 or above, you can be sure that they are completely closed. In my system, cycling once per hour, the mains with 1" insulation on them, even on cold rooms, never cool down to below 150 degrees F. So, in one of the trial setups in my system, I found the Gortons just didn't do the job the were supposed to, except on a cold start.
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
  • PeteysPeteys Member Posts: 62

    Boiler only short cycles when it reaches 12 oz., down to 4oz., etc, etc. I would say that it takes about twenty minutes for that to happen from a cold start. did notice yesterday that riser off dropped header feeds short main first as does Chris,s, possibly stealing steam from the long main?

    Going to have to repipe or try and adjust pitch in the next month or so. Not going to be fun. :).

    Boiler starts to cycle after both mains are hot and Gortons are closed, as they should?

    It took 30 minutes for the radiator to get hot on the 3rd floor yesterday with a new maid o mist C installed instead of hoffman 40, which is much better. Going to try a D and see if that helps even more but I know my real issue at the moment is water in that long main.
  • ChrisJChrisJ Member Posts: 8,599
    edited April 2014
    30 minutes with C

    Holy smokes, 30 minutes even with a size C?

    Did you remove or reduce the main venting on the short main and does the long main start to get hot right away or does it take a long time, seeming like all of the steam is going to the short one?

    My boiler isn't oversized but rather is sized perfectly, and 30 minutes after I start producing steam all of my radiators are completely full or close to it. Once steaming it usually takes 2-3 minutes to get steam to all of my radiators meaning the pipe going to every radiator is hot, not the radiator it self yet.

    As others have said swooshing sounds are never good, that's your steam dying before it even gets to the war. Killing steam is the same as burning money so you need to fix that as painful as it may be.

    Just to keep everyone on the same page, the times I gave are after the boiler starts producing steam. I don't include the time it takes to heat the water up as that's variable and very dependent on when the last time the boiler was on. After being off for a few days it took 20.5 minutes to start steaming from a cold start + the time to get the steam down the pipes. On cold nights it may only take a minute or two to start steaming.
    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

    Steam system pictures
    Central air project pictures
Sign In or Register to comment.


It looks like you're new here. If you want to get involved, click one of these buttons!