Adding a filter disc to your fermenter

Vacuum breaker pressure relief valveA vacuum breaker and pressure relief valve can be a useful accessory to help insure against damage to a fermenter. A vacuum, caused by a cooling of liquid or gas inside the fermenter can pull the sides in, and pressure building up from expansion or gas produced during fermentation can push the walls out. In either situation, the fermenter can be damaged, possibly beyond repair. The BREWHA Vacuum Breaker and Pressure Relief valve serves to protect your investment by opening when either 25mmHg of vacuum or 3psi (for 3-in-1 fermenters) or 14.9psi (for 4-in-1 fermenters) of pressure occurs in the fermenter. 

When the pressure builds over the limit, the relief valve is pushed open, letting gas escape. It is important to note that a safety relief valve should always be used in conjunction with a blow off tube or air lock, and not be used as the primary means for release of gas. The reason, is that in the event where a fermenter was overfilled (and/or fermentation too vigorous) krausen (foam) could enter the opening mechanism and prevent the valve from operating properly. When a vacuum builds up, it pulls down on the valve, opening the valve and letting air into the fermenter. 

fermenter filterIf one wants to filter the air that is being drawn into the fermenter during cooling (to remove any microbes) Filter discs can be employed to filter the air. Filter discs come with different pore sizes, material construction and sizes. The kind that are necessary for fermenters have a pore size of 0.22μm or smaller which is the size necessary to filter out microbes, and a suitable material that can can be sanitized (boiled in water or washed with an acid sanitizer like Star San). The disc size should be large enough to completely cover the silicone ferrule gasket so that when installed will form a seal all the way around, but not too large (e.g. larger than the ferrule) so that it might wrinkle or stretch when the valve is installed, forming an opening that unfiltered air could enter into the fermenter. ALWAYS maintain a primary means of gas exchange (ie. an open blow off hose) and DO NOT allow the filter to be soiled as it may plug and prevent gas exchange. 

fermenter gas filterThe filter disc should be installed on a port that is separate from the pressure/vacuum relief valve, or if on the same port, use a 'tee' to eliminate the risk that the relief valve will be prevented from working properly due to a soiled filter disc. See the picture above for the two installation recommendations. The fitting holds the filter disc in place. Once chilling is completed, the filter disc can be removed and the fitting replaced with a blow-off hose. (If using the tee, this step is not necessary as the blow-off hose can be attached to the other ferrule/port.)

Note: Filter discs may be packaged with wax paper discs separating the teflon discs—DO NOT use the wax paper discs as filter media as they will not let gas pass through.

Filter discs can be purchased here.



  • Pressure relief is a very important activity we all need to take care of. Even at home, we should take care of it whether it is about the vaccum breaker or some other material. Learned a lot from this post regarding pressure relief. Thanks a lot!
    Relief Valve Release Event

    Relief Valve Release Event
  • Dear Preecha, the filters permit 3LPM at 0.04bar, an initial IPA bubble point at 1.2bar and retain that through sterilization for 30min at 121C.

    BREWHA Equipment Co Ltd.
  • Dear Sir/Madam,
    My customer required vacuum breaker filter, 0.2 um PTFE, flow rate 4 Nm3/min, flow resistance < 6 KPa, Max Temp 70 degreeC, Max Operation Pressure – 0.096 MPa
    Could you support for this enquiry.
    I’m looking forward to hear your reply.
    Best Regards,

    Preecha Peerasuwan
  • Being made of teflon, under normal use and with careful handling they can last a long time. Careful handling means installing them so as to not cause tearing/ripping, and ensuring your fermenter has sufficient headspace so the krausen does not reach and plug the microscopic pores.

    BREWHA Equipment Co
  • How long do the last, eg. When using ones or twice a week?

    Deventer R.

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