Pressure Control: PRV vs PVRV

In the world of fermentation, maintaining proper pressure control is crucial for both product quality and equipment safety. Two common devices used in this process are Pressure Relief Valves (PRVs) and Pressure Vacuum Relief Valves (PVRVs). Let's break down their differences and help you choose the right option for your fermenting needs.

Pressure Relief Valves (PRVs)

PRVs are designed to release excess pressure when it exceeds a predetermined threshold. The built-in valve opens automatically when pressure reaches the set point, protecting your vessel from over-pressurization. PRVs are best used for standard fermentation processes where only positive pressure relief is needed.

Positive Pressure Scenarios

The most common scenario where positive pressure is created is during active fermentation, especially during days 1-4 when fermentation is the most vigorous as the yeast convert sugars to CO2 and alcohol. Pressure can reach 5-15 PSI depending on fermentation vigor, and without proper relief, the excess pressure can cause harm, damage equipment, or cause leaks.

Temperature increases can also cause a positive pressure situation. A sudden failure of your glycol cooling system, for example, can drive liquid and gas expansion due to heat. Pressure transfers, i.e. moving beer between vessels using CO2, also introduces pressure to the tank environment and needs to be properly controlled.

Pressure Vacuum Relief Valves (PVRVs)

PVRVs are dual-action valves that manage both positive pressure and vacuum conditions, by releasing excess pressure AND allowing air intake when negative pressure occurs. PVRVs are a must for professional brewing operations but can also protect homebrewers using advanced fermentation techniques.

Negative Pressure (Vacuum) Scenarios

Any scenario where rapid cooling occurs can cause negative pressure inside a fermenter. When beer inside the tank is cooled after hot-side operations or during crash cooling, the gas inside the tank contracts as the temperature drops, which can cause suck-back or tank deformation if not properly vented. Crash cooling an ale, for example, typically decreases tank pressure by 5-7 PSI, so ensuring your tank has vacuum relief capabilities (or alternatively an equal amount of positive pressure) before crash cooling is critical.

Tank draining during racking operations or during the clean-in-place (CIP) process can also cause liquid leaving the vessel without adequate air or gas to replace it. A PVRV can also help prevent a potential tank collapse by relieving the negative pressure created during these transfers.

Making the Right Choice

Vessel Size: Larger tanks benefit more from PVRVs due to increased vacuum risks
Process Complexity: More complex operations usually require PVRVs
Budget: PRVs are more cost-effective for basic setups
Future Plans: Consider future brewing techniques you might implement
Peace of Mind: PVRVs offer complete protection in all scenarios

Our popular JF8 jacketed unitanks can be customized with either a PRV or PVRV, depending on the brewer's needs. Check out our broad selection of fermenters and pressure-control fittings here.