How to set and adjust a spunding valve

Spunding valves are a relatively simple but crucial bit of equipment when dealing with pressure fermentation. A spunding valve allows you to set a predefined level of pressure within your pressure fermenter which the valve will maintain by venting or releasing any pressure above this predefined level.

Kegland Blowtie Spunding Valve fitted to keg

For example, if the spunding valve is set to 10psi, it will not vent any gas and allow the pressure to build to 10psi - after which it will begin venting any additional air/pressure that builds up so a steady 10psi is maintained throughout the fermentation.

The spunding valve I'll be using in this example is the KegLand integrated gauge blowtie spunding valve - if you have a different make/model that is fine - the underlying process will be the same regardless of what type of spunding valve you have.

Before we start - I've noticed on my particular spunding valve that the gauge is wildly inaccurate so I won't be using it for any reference - I'll be using the low pressure gauge on the CO2 regulator attached to my gas bottle.

Also notice on this particular spunding valve there's an arrow on the side indicating the direction gas should be flowing through the valve - make sure you have it installed the right way otherwise it won't function correctly.

Note the arrow circled in black showing the direction gas should flow through the spunding valve

1. Pressurise a keg or smaller vessel to the set pressure you want to set your spunding valve to. A good starting point for pressure fermentations is 10psi. As previously mentioned, I use the low pressure gauge on my CO2 regular to set this pressure in the vessel.
   (You can use a PCO 1881 carbonation cap tee piece (like this) in order to be able to use a smaller soft drink bottle instead of a 19L keg to save on your gas usage).
   
   
2. Ensure the diaphragm on the spunding valve is fully closed (so it won't vent any air/gas). On my valve, this means winding the adjustment handle clockwise as far as it will go.
   
   
3. Attach the spunding valve to the gas post of your keg or carbonation cap tee piece. There should now be a reading on the gauge of your spunding valve showing it has pressure (hopefully around 10psi).
   
   
4. Attach a short hose piece to the outlet of the spunding valve and submerge the end of this hose piece into a glass of water.
   
   
5. Begin slowly unwinding/opening the diaphragm adjustment on your spunding valve until you start to see bubbles in the glass of water you have the hose piece submerged in - this indicates that gas is being released by the spunding valve. On my spunding valve, this adjustment is done by slowly turning the yellow handle anti-clockwise.
   
   
6. Once you see the bubbles appear, you know the valve is releasing pressure at 10psi. Make tiny adjusments on the spunding valve again to close it until the bubbles stop. This way, it will begin releasing once pressure exceeds 10psi, not at 10psi.
   
   
7. Your spunding valve is now set. Take care not to bump/move the adjustment on it when disconnecting, storing or reconnecting

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