what size main vent?

Paul_87

I have a 30' of 3" main feeding two 2" mains that are 60 and 40 feet long. Also there are 1 1/4" dry returns that are a total of 130' with crossover traps and the ends of the two 2" mains to vent them. Right now I have a Gorton 2 and it is definantly not enough.

Brad White_200

Venting

The main vent, just to be clear, will vent only that main, not what is served off of it. Any vent will only vent what is upstream of it, so those out-feeding 2" lines will need their own venting solution.

That said, your 30 feet of 3-inch pipe will hold 1.54 CF of air. A Gorton #2 at 2 ounces pressure will vent that in less than a minute.

Are you sure it is just a lack of venting?

Your 60 foot and 40 foot 2-inch runs will hold 1.4 CF and 0.93 call it 1.0 CF respectively. A Gorton #2 would be plenty for each but you could use a pair of #1s on the shorter run instead. I assume that the radiators are properly vented of course.

The dry returns, if all together, hold about 1.35 CF of air, so a #2 would be plenty to get that vented in under a minute.

Not knowing any particulars, I do have to ask if it might be something else, either alone or in concert with the venting.

Paul_87

Brad

It is a vapor system. There is only one vent location. All of the mains are vented into one dry return with crossover traps and at the end of that dry return is the vent before the dry return goes down into the wet return. Thanks

Brad White_201

NOW you tell me!

That said, I figured out your total pipe volume from what you have given me at about 5.3 cubic feet. A single Gorton #2 at 2 ounces would vent that ideally in about three minutes.

Then again, do you have your trap venting rates? Those can be between 0.5 and 1.5 CFM each, so your outlet vent (the Gorton) should replicate that venting rate. If not, you are backing up as you may be finding. You cannot vent faster than your slowest vent.

How many traps and of what make?

gerry gill

whose vapor system is it?

sounds like a dunham style configuration..what size tapping is the single main vent screwed into? is it 3/4''? if its 3/4'' maximize its venting capacity with 4 gorton #2's..if its 1/2'' you'll max out with two #2's.

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