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UDS vent size


Joined Jan 13, 2019
I have built around 7 UDS builds over the last 10 years, several for myself and a few for friends. I know what works but I have a question about a new idea for a build. I started out with the typical build (4 intakes 3/4" in size). I then built a full size UDS using a couple 1" ball valves with the 90 degree elbow and an upright stack. It worked but I felt like the air intake was a little restricted. The last several I have made used stainless sliding draft doors and that's enough intake and THEN some. I have fallen in love with my mini UDS which started out as a 55 gallon drum that I shortened so that it doubles as a grill also. It has 2 sliding draft doors which is overkill. one door at 1/8 open can maintain 250-275 degrees. I am in the mood to make another shortened drum that's a hair taller than my current one to allow for taller meats like turkey and spiral cut hams. With this new build I am yearning for a steam punk design. I have a 1 1/4" ball valve and a 4" brass extension pipe with a brass 90 degree elbow. My past experience with a set up like this (only using 1" valves, elbows and pipes on a full size drum) was that the upright and the 90 degree elbow restricted airflow. Can anyone shed some knowledge for me if 1 of these 1 1/4" valves on a 90 elbows with a shortened 55 gallon drum will be enough intake for 350+ degrees or should I put 2 or more in? This is a thought for a spring project BTW as I don't even have a drum yet or the gumption to start till late spring.


Master of the Pit
OTBS Member
Joined Jan 7, 2017
Well I run 3x 3/4 which is enough to run my full size at over 600 degrees if I leave them all open long enough.

Your air inlet would be 55% the size of mine, but you'd be running a smaller unit. Without doing the match I would think it would handle it. Maybe would depend on the size of your coal basket and initial number of hot coals that were added to it.

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