Portable Propane to Butane Pressure Regulator

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Introduction

Most portable stoves are designed to run directly on butane canisters. These canisters deliver fuel at their natural vapour pressure, which is usually sufficient in warm weather but drops rapidly as temperatures approach freezing. At 0 °C (32 °F), a butane canister produces only about 29 kPa (4 psig), and by −10 °C (14 °F) the pressure falls to around 10 kPa (1.5 psig), often too weak to sustain a flame.

Propane is different. At 0 °C (32 °F), propane still provides about 480 kPa (70 psig), and at −20 °C (−4°F) it maintains around 275 kPa (40 psig). In fact, propane remains gaseous down to −42 °C (−44 °F). This makes propane far more reliable in cold conditions. The difficulty is that propane pressure is too high for stoves built for butane. Feeding raw propane can damage the stove or trigger its built-in safety shut-off, which typically activates between 400 and 600 kPa (58–87 psig).

The Solution

The answer is to use a fixed-output high-pressure regulator. This regulator takes the high and variable pressure from a propane cylinder (typically 690–830 kPa / 100–120 psig at 20–30 °C (68–86°F )) and reduces it to a steady 200 kPa (29 psig).

This output is very close to the vapour pressure of a butane canister on a hot day (about 170–207 kPa / 25–30 psig at 30–32 °C (86–90 °F). In other words, your stove now sees the same pressure it was designed for, but delivered from propane rather than butane.

  • For simple stoves (no internal regulator), this keeps the flame safe and predictable.
  • For stoves with micro-regulators, it prevents damage by ensuring the internal components never have to deal with the dangerously high pressure of unregulated propane.

Because the regulator is a fixed output, no adjustment is necessary. The pressure will always be around 200 kPa (29 psig) once connected.

Cold Weather Advantage

The true benefit appears in cold weather. Butane quickly becomes unusable below freezing, while propane remains strong. With the regulator, your stove always receives 200 kPa (29 psig), whether the cylinder is in summer heat or winter frost.

For portable stove users, this means:

  • Reliable performance down to at least −20 °C (−4 °F), well beyond the range where butane fails.
  • Safe operation in summer, because the regulator caps the pressure below the stove’s safety cut-off.
  • One fuel and one setup usable year-round.

Safety Notes

  • Always test all connections with soapy water before lighting the stove.
  • Ensure that hoses and adapters are LPG-rated.
  • If you connect a gauge to the regulator, it typically shows gauge pressure (relative to atmospheric pressure). A reading of 200 kPa means the stove is receiving 200 kPa above the surrounding air pressure.
  • Do not bypass the regulator. Direct propane connection to a butane stove is unsafe.

Conclusion

A fixed-output propane-to-butane regulator transforms a portable stove. It protects both simple and micro-regulated stoves, prevents overpressure, and makes propane practical for year-round use. With propane staying gaseous down to −42 °C (−44 °F), this solution ensures that your stove lights easily and runs consistently in conditions where butane would fail.

Parts

The following off-the-shelf parts are readily available and easily assembled. The following parts can be combined to create a backpack portable regulator. The following setup connects a portable propane bottle, regulates the gas, and terminates at the UNEF connector used with butane tanks. Because the UNEF connector is not self-sealing, including a ball valve shut-off valve is necessary.

Portable Propane to Butane Regulator
  1. Connector: 1/4″ Male NPT Thread x 1″-20 Female
  2. Ball Valve: In-Line Ball Shut Off Valve, Quarter Turn, 1/4″ Male NPT (MNPT) X 1/4″ Female NPT (FNPT)
  3. Regulator: Single-Stage High-Pressure Regulator
  4. UNEF Connector: 7/16-28 (m) to 1/8″ NPT (f)1
  5. Propane Bottle: Flame King 1/4-lb Empty Refillable Propane Cylinder Tank

Not numbered:

All of the parts are combined in the numbered order above. Teflon gas pipe thread sealant is used for every combined part. It is important to wind the tape in the direction of the threads. The NPT threads are meant to be tightened until they seal (about two turns after hand tightening). Check for leaks using a leak detector.

Connectivity Order

A specified order is needed for a connection to practice safe operations continuously. We practice safe operation by connecting the propane tank last and disconnecting the propane tank first. While unnecessary, we included a ball valve to ensure propane does not suddenly flow out of the UNEF connector when the propane tank is connected. If you follow the proper order of connectivity, the ball valve is unnecessary, but we prefer to use it as a layer of protection. You are dealing with flammable gas.

  1. The appliance is the first to connect to the UNEF connector (4) above.
  2. Check to ensure that the ball valve (2) is closed.
  3. Connect the propane tank connector (1) to the propane tank (5).

Operation: Starting

  1. Check that the on/off valve on the appliance is closed.
  2. Open the ball valve (2).
  3. Open the on/off valve on the appliance (if equipped).2
  4. Light the appliance

Operation: Shutdown

  1. Starve the regulator and the appliance of its fuel by closing the ball valve (2).
  2. Close the on/off valve on the appliance (if equipped).
  3. Disconnect the propane Tank (5).
  4. Disconnect the appliance.
  1. This part is available in a thread size smaller than the rest of the connectors. You must use 1/4 NPT x 1/8 NPT Male Adapter Fittings to connect the regulator to the UNEF connector. ↩︎
  2. If the appliance does not have an on/off valve, be prepared to light it. ↩︎
LPG Mix Vapour Pressure (metric) — Greyscale.zone Calculator

LPG Mix Vapour Pressure (metric)

Antoine equations (NIST) + Raoult’s law. Inputs are temperature (°C) and mass percentage of propane in the liquid. Outputs both absolute and gauge pressure.

Quick temps:
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Result at 20 °C

Pure-component Psat (absolute)
Propane
– kPa
n-Butane
– kPa
Mixture (Raoult’s, ideal)
Absolute
– kPa
Gauge (vs 101.325 kPa)
– kPa

Assumes ideal liquid solution; liquid composition given by mass % is converted to mole % internally.

Show table (0, 10, 15, 20, 25, 30 °C)
Copies the current table (using your Patm and settings)
T (°C) Propane Psat (kPa) n-Butane Psat (kPa) Mixture Absolute (kPa) Mixture Gauge (kPa)

Notes: Antoine constants from NIST; temperature in kelvins; P* returned in bar and converted to kPa. Mix via Raoult’s law on mole fraction derived from mass %. User-facing pressures shown as gauge unless labelled absolute. Use certified regulators and hoses. This tool is informational and does not replace professional engineering advice.

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