A draft beer trunk line, also called python, is the insulated bundle that carries beer and circulating glycol from the cooler to a remote tower. Get the product-line count, glycol circuits, internal diameter and route right before ordering. Those choices determine whether a long draw system can hold temperature, balance correctly and stay serviceable after the walls are closed.
In this article
- What a draft beer trunk line does
- How to count product and glycol lines
- How to choose the inside diameter
- Why insulation and bundle construction matter
- What to map before ordering
- Your trunk line order checklist
What is a draft beer trunk line, and when do you need one?
A trunk line is not just a group of beer hoses wrapped together. It is a factory-built bundle of product lines, glycol supply and return lines, insulation and a protective jacket.
Glycol travels beside the beer lines in a closed loop to protect beer temperature on the way to the tower. The beer still needs the correct gas pressure and total restriction to pour properly. That is why trunk line is part of the system design, not a one-size-fits-all commodity.
Micro Matic explains that a properly built trunk line uses exact-fit insulation, foil and a protective jacket to help keep beverages cold and reduce condensation. Their trunk line overview is a useful reference for the construction details worth comparing.
How many product and glycol lines should a trunk line have?
Start with the number of beverages you need at the remote tower, then add room for the layout you are actually building. A six-faucet bar needs six product lines. A 12-handle taproom needs 12. Do not order a 10-product bundle for an 11-product job because one unused tap is still more useful than opening a finished route to add a new run.
Then verify the glycol circuit count with the equipment schedule. The glycol lines are not spare product lines. They circulate coolant through the bundle, and the required loop design depends on the number of product lines, route and power-pack design.
SKU 826-CDI642-BF. A cut-to-length, 1/4-inch I.D. bundle for a six-product, two-glycol-line configuration.
How do you choose draft beer trunk line diameter?
The three common product-line diameters are 1/4 inch, 5/16 inch and 3/8 inch I.D. Smaller product lines create more restriction. Larger product lines create less. The correct choice depends on the total balance calculation, including actual run length, elevation, beer style, dispensing pressure, jumper line and tower choker line.
Do not try to fix a restriction problem by simply raising CO2 pressure. On a long draw, more pressure can affect carbonation. Long systems may require blended gas or a beer pump based on the full design. This long-draw sizing primer is useful for understanding how product-line restriction, elevation and the choker work together.
| Decision | What to verify | Why it matters |
|---|---|---|
| Product-line I.D. | 1/4 in., 5/16 in. or 3/8 in. | Changes restriction and must fit the balance calculation. |
| Product count | Every current and planned faucet | Avoids unused dead ends or an expensive reroute later. |
| Glycol circuits | Power-pack and route design | Keeps cooling circulation matched to the bundle. |
| Length | Installed route, not a straight-line guess | Trunk line is cut to order and cannot be returned. |
SKU 826-CDI852-BF. A cut-to-length, 5/16-inch I.D. eight-product bundle with two glycol lines.
Why do insulation and bundle construction matter in a long draw?
Cold beer in the cooler is only half the job. The bundle must keep heat away from the product lines on the route to the tower. Insulation, foil, the outer jacket and close contact between glycol and product lines work together. A damaged jacket, crushed bundle or exposed section can make a correctly sized power pack look like the problem.
That is why cheap knockoff assemblies are a poor place to save money. A long draw route may sit above a hot kitchen, through a ceiling chase or near equipment that adds heat. The trunk line needs to protect the beer all the way to the faucet, not only during the first few feet out of the walk-in.
What should you map before the trunk line is ordered?
Measure the real route from the cooler to the tower. Include every turn, riser, ceiling path and service loop. Then mark where the bundle will be supported, where it passes through a wall or conduit, and how a technician will reach it later. A short straight-line measurement rarely matches the installed footage.
- Count every live and planned product line. Include wine, cocktails or non-alcoholic beverages if they share the bundle.
- Record the furthest tower and elevation changes. The most remote faucet is usually the one that exposes a design issue first.
- Confirm the glycol loop and power-pack capacity. Product count and loop design affect cooling load.
- Plan gentle bends and protected penetrations. Avoid kinks, crush points and a route that cannot be serviced.
- Get the cut length right before purchase. These trunk line products are cut to order and non-returnable.
SKU 826-CDI1234-BF. A cut-to-length 12-product, four-glycol-line configuration for a larger designed system.
What should be on your trunk line order checklist?
Before you order, send your installer or draft technician the product count, proposed product-line I.D., installed route length, elevation, tower locations, glycol circuit plan and power-pack model.
For a system that needs glycol cooling, use our glycol chillers and long draw cooling systems collection alongside the trunk-line selection. Our glycol chiller sizing guide covers the power-pack side of the decision.
Related guides
- Glycol Chiller Sizing Guide: 7 Checks for Long Draw Systems
- Fix Foamy Beer: Causes and Fixes for Draft Systems
- What You Should Know About Planning a Beverage System
Need a second set of eyes before you order trunk line?
Send us the faucet count, installed route, elevation and cooling equipment. We will help you narrow the right bundle before it is cut to length.
Shop draft beer trunk line →Expert advice and customer service. Free technical support for all orders.
Frequently asked questions
What is a draft beer trunk line?
A draft beer trunk line, also called python, is an insulated bundle of beer product lines and glycol lines that carries beer from remote keg storage to a draft tower. It is used in glycol-cooled long draw systems.
How many glycol lines do I need in a beer trunk line?
The needed glycol circuits depend on the product-line count, installed route and power-pack design. Confirm the glycol loop with the complete system schedule rather than treating glycol lines as extra beer lines.
What size beer line should be inside trunk line?
Common trunk-line product-line sizes are 1/4 inch, 5/16 inch and 3/8 inch I.D. Choose the size from the full balance calculation, including run length, elevation, beer pressure, tower choker and total restriction.
Can draft beer trunk line be cut to length?
Yes. The Barriermaster Flavourlock trunk line products shown here are cut to order and priced per foot. Verify the installed route before ordering because cut-to-length trunk line is non-returnable.
