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Balancing Draft System - Devil in the Details

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  • Balancing Draft System - Devil in the Details

    Hey everyone,

    I'm in the process of designing our draft system and I've read through most of the pertinent posts here and also the DBQM. There's some conflicting opinions about choker lines and since ours would be buried in the ceiling I'd prefer not to use vinyl chokers so I don't have to replace them. My main question is:

    If I'm running 1/4" trunk lines, can I also run 1/4" vinyl jumper lines from keg to trunk? Or are there issues with flow rates going from more restrictive tubing to less restrictive?

    Here are the layout basics:
    Tap tower provides 12.8 lbs resistance
    Total lift is 1.5'
    Trunkline runs 12' from the cold room to the tower which hangs from the ceiling
    I'll have a power pack cooling the entire trunkline run, regardless of length.

    Assuming a worst case of 2.6 vols/CO2 at 38F = 12.4 psi
    With a 70/30 CO2/Nitro beverage gas I get a dispensing pressure of 24 psi

    The DBQM calculations give me a couple of balancing options:
    - 18' of 1/4" barrier line (and just coil the extra in the cold room) and 6' of 1/4" vinyl jumper
    - 27' of 1/4" barrier line and 6' of 5/16" vinyl jumper
    - 31' of 1/4" barrier line and 6' of 3/8" vinyl jumper

    I'd prefer the shorter trunk line but again, not sure if there's an issue going from high-resistance vinyl to low-resistance barrier even if they're the same ID.

    Thanks in advance!

  • #2
    Going from high restriction to lower restriction can cause break-out. There's a pressure differential involved when restriction drops.

    OTOH, I think we all use flexible tubing to go from the keg couplers to the the trunk lines. I use 3/8" for both and have no problems with break-out. I'm not sure there is that much difference between restriction of flexible vs. trunk line.

    I'm currently using beer pumps in my systems. The flexible line goes from the keg coupler to the beer pump, then the trunk line connects directly to the output of the pump. This eliminates any chance of a pressure drop at the connection. I'd strongly advise using beer pumps for any distance greater than 8-10 feet. Not only do they make for perfect pours and eliminate the need to use mixed gas for push, they make recirculating line cleaning a breeze if you use a reverser valve on every other pump.

    Burying your lines in the ceiling is asking for problems down the line. At some point, you will need to replace choker lines. If you can't provide a trapdoor or other access from above, reconsider your routing.
    Timm Turrentine

    Terminal Gravity Brewing,
    Enterprise. Oregon.


    • #3
      Can you get a gas blender to give you a better ratio? This way you can dial in the gas percentages to keep your pressure where your system needs it to be to keep your lines as short as possible?