Why do you want your main steam vent to be at least 6" higher than the horizontal return?

kiemside

I have a one-pipe steam system. I have two main vents, one for each return (one from the front and one from the back sides of the house). The vents are current situated at the horizontal return. I just bought two Barnes & Jones Big Mouth Vents to change. I keep seeing the recommendation of putting your main vent at least 6" higher than the horizontal return but I never see any explanation. Why do you want to have your vent at least 6" higher than the horizontal return?

Steamhead

So if there's any water hammer in the pipe, the vent will be up high enough that it shouldn't be affected that much.

kiemside

thanks

EBEBRATT-Ed

You want to reduce the possibility of condensate (water) getting into the vents. Keep it high and dry