The Blow Tie Spunding Valve is used to release excess pressure on a pressurized fermenter or from a receiving keg during pressure transfers. This diaphragm spunding valve is much more accurate than the spring and poppet style, and works much better at lower pressures.

Pressure Fermentation

Pressure fermentation is becoming more and more popular at the homebrew level, but in order to do it safely and accurately, you need a way to release excess pressure. You'll pressurize your vessel to your desired psi, but once fermentation begins and those hungry, active yeast start creating CO2, the pressure inside the vessel will increase. Attach a spunding valve and set it to your desired pressure, and it will blow off when the pressure gets to high and close up again when it's back to your desired psi.

Pressure Transfers

Even if you don't have a pressurizable fermenter, you may have done pressure transfers from keg to keg during filtering or after fining. During pressure transfers, it's a good idea to have a bit of head pressure in the receiving keg, especially if you're transferring beer that is already carbonated. Having a spunding valve in place will allow you to consistently control the head pressure and give you more consistent results, without losing carbonation in the process.

Diaphragm vs. Poppet

With the poppet style spunding valve, a spring pushes against a poppet to keep the valve closed. When the poppet lifts up to open, the surface area the gas pushes against becomes larger, and the spring has to work harder to push the poppet down and reseal the valve. This can lead to more gas being released than intended, and the remaining pressure in your vessel may be at a lower psi than your spunding valve’s set psi. 

Instead of a poppet, the spring inside the BlowTie pushes against a diaphragm, which has an immensely larger surface area. This means the surface area that the gas pushes against while the diaphragm is closed is significantly closer to the surface area it pushes against when the diaphragm is open. This leads to higher accuracy, and the remaining pressure after excess gas is released will be much closer to your set blow off pressure. 

Set Up

The BlowTie spunding valve comes with 8 mm Duotight fittings on the inlet and outlet, and we recommend using it with EVABarrier 8 mm OD tubing (D1717 or D1718). You'll also need the flare Duotight fitting (DUO106) in order to attach it to a ball lock or pin lock. Dialing in your desired pressure is very simple. Although you would ideally use the BlowTie with the Push-In Pressure Gauge (D1160) and Duotight Tee Fitting (DUO109), as seen in the example photo, you can easily set the blow off pressure without it. To do this, simply pressurize an empty keg to your desired psi using your CO2 regulator. Before attaching the BlowTie to the gas post, be sure to turn the dial clockwise until it is fully closed. Once attached, slowly turn the dial counterclockwise until gas starts coming out, then slightly turn the dial back to stop the gas flow. The BlowTie is now set to your desired pressure.

Please note: the BlowTie does not come with the pictured accessories. Please see "You might also like" below for the other products shown in the example photo.