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Venting at the dry return

I have read a LOT of posts about venting yet I still have a few questions.

I have two dry returns and each has a single small vent at each elbow that drops to the wet return. I don't see or know of other vents/traps on the mains because they are in the walls and ceilings. @Abracadabra has kindly explained at method which I can add vents in iterations to find the optimal number but after buying a couple of Gorton #2 today and seeing how expensive they are I am tempted to just plop one on each return and say that is good enough "for now".

My main question is what will I experience heating wise if this is not enough venting? Is it just a matter of how fast the radiators will heat up? I am willing to add more, but later. There seems to be a lot of debate as to where the venting should take place and the wisdom of ever venting at this location but this is what I have and where they are going to stay.

Along the same lines I will using a couple of elbows and an antler of sorts (as suggested) to locate the Gorton #2's away from that elbow. But in other threads I read of vents needing to be 15" away from the main. Does that apply here - I mean should my antler be at least 15" long? These vented elbows are already a good 40+ inches over the water line.


  • KC_Jones
    KC_Jones Member Posts: 5,737
    There is a point of diminishing returns on venting. Once you are venting at the same rate as an open pipe more vents won't do anything. The vents get the steam to the radiators so without enough venting the steam moves slower and you burn fuel NOT heating your house. This is why it is said to vent the mains as fast as possible. I posted some theoretical numbers a while ago, but here is a rough break down for illustrative purposes. If you save 10 seconds getting steam to your radiators on every heat call, you get on average say 10 heat calls per day that is 100 seconds per day. Say maybe 6 months of heating season, 30 days per month. That would total up to 5 hours of fuel times the firing rate of the boiler, multiply that by the cost of gas. You see how it can add up and that vent can seem really cheap. The best way to judge this on your system is to take the vent off completely and leave the pipe open. Fire the boiler then time how long it takes for the steam to get to the end of the main, don't start timing until the header is hot (don't burn yourself). After you have this time add venting until you get as close to that number as you can. This will be the best you can do. As far as the antler, yes try and get back from the connection at the tee. The reason for moving them back is to keep the steam from beating them up.
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