Adding a filter to a Vacuum Breaker and Pressure Relief Valve
A 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 a 25mmHg of vacuum or 3psi of pressure occurs in the fermenter.
When the pressure builds over 3psi, 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. While it is desirable to prevent a vacuum from building up to the point where it could damage the fermenter, it is not desirable to let unfiltered air be pulled into the fermenter as airborne microbes could contaminate and spoil the beer. The solution to this conundrum is to install a filter disc between the valve and fermenter.
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.
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.