Adding a Main Vent

Alan(CaliforniaRadiant)Forbes

This is a job next to the Presidio in San Francisco. The system must have been slow to heat since there was no main vent.

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Alan(CaliforniaRadiant)Forbes

After

We tapped the pipe and added this vent.

Thanks for all your help Noel, Steamhead, et. al.

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Steamhead

And

you looked like a genius to the owner, right?

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Lew

main vent

Can you tell me what kind of vent that is? Thanks

Steamhead

That looks like a Hoffman #75

They don't paint them green anymore.

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Alan(CaliforniaRadiant)Forbes

Hoffman #75

main vent although Steamhead told me to use a Gorton #2 because there is greater resistance on a 2" main than a larger main. So why didn't I use a Gorton? The Hoffman 75 "was all they had on the shelf". My face is red.

Owners don't know the difference since they just bought the house. It's one of those jobs where I haven't met the owners yet; I am only in communication with the GC and the AIA. There's a budget for steam boiler work and as long as I don't go over that amount and the system works, they're happy.

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Unknown

4 of those

equal one #2 Gorton. Nice job! It's great to see steam systems cared for.

Noel

Alan(CaliforniaRadiant)Forbes

That's seriously bigger

Is is still ¾" pipe threads or larger?

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Unknown

1/2" MPT

btc

Tap size

Does it matter what size tap is drilled? 1/2", 3/8" ? Lost Art says add T to ensure a very large opening to main vent. If vent opening on Hoffman 75 is a certain (small) size, why would you need to tap anything larger than that?? Just curious. Thanks.

Steamhead

I've used smaller sizes

for the smaller vents and they work OK as long as you're not at the very end of the main. Alan had plenty of room to get his drill into the top of the pipe on this one, but this isn't always possible so going into the side and elbowing up works too. I have many vents in the Baltimore area installed this way, and have never lost one to water-hammer or anything else.

The ideal thing to do is cut and thread a tee into the main, as described in Lost Art. Unfortunately we can't always do that.

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