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In the management of an isobaric cellar, mastering fermentation pressure is both an economic and qualitative key lever.
Using a spunding valve (pressure‑regulating valve or guillemeteur) makes it possible to trap the CO2 naturally produced by the yeast at the end of fermentation, ensuring fine, even carbonation without consuming industrial gas.
It also preserves volatile hop aromas and prevents tank deformation during pressure transfers. Discover our comparative guide to select the professional pressure‑control solution best suited to your brewery.
1. Spunding Valve vs PRV Safety Valve: Don’t confuse safety with regulation
Although both manage pressure on an isobaric fermenter, their roles are fundamentally different:
- The PRV safety valve (Pressure Relief Valve): A passive safety device factory‑calibrated (e.g., 2.5 or 3.0 bar). It remains closed at all times and only opens suddenly in the event of critical overpressure to prevent tank damage.
- The Spunding Valve (Guillemeteur): An active regulation tool. Equipped with a micrometric adjustment knob and a pressure gauge, it continuously vents excess gas as soon as pressure exceeds the chosen setpoint (e.g., 1.2 bar for a Lager or 0.8 bar for an Ale), ensuring perfect natural saturation of the wort.
2. Selection criteria for your brewery: Mechanics, hygiene and automation
Depending on your workshop setup and fermenter size, three major categories of spunding valves compete on the market:
- Compact membrane/spring spunding valves (e.g., BlowTie): Affordable and lightweight, ideal for small tanks, PET fermenters or mobile conditioning units. Easy to adjust but require regular preventive cleaning, as foam deposits can clog the membrane.
- Stainless‑steel guillemeteurs with integrated airlock (e.g., Brewtools / Pro Inox models): Made from 316L stainless steel with Tri‑Clamp connection (TC 1.5" or TC 34 mm), they are the standard in craft breweries. The transparent body (airlock) allows visual monitoring of degassing while maintaining a sterile barrier. Fully disassemblable for CIP or autoclave cleaning.
- Automated pneumatic regulation systems (e.g., Brewtools FCS integration): Connected to a digital pressure sensor and controlled by a solenoid valve, these systems allow remote programming of progressive pressure stages (e.g., fermentation at atmospheric pressure followed by gradual rise to 1.5 bar for spunding).
3. Comparison table: Which spunding valve should you install on your isobaric tanks?
| Type of Spunding Valve | Pressure Range & Connection | Cleanability / Hygiene | Brewery Profile / Recommended Use |
|---|---|---|---|
| Compact Membrane (BlowTie) | 0 to 1.5 bar / Duotight or Barb Fitting | Manual disassembly, sensitive to Krausen overflow. | Nano‑breweries, PET fermenters, service‑keg pressure control. |
| Stainless Sanitary Guillemeteur with Airlock | 0 to 2.2 / 3.0 bar / Tri‑Clamp 1.5" or TC 34 mm | Excellent. Fully disassemblable, CIP‑detergent compatible. | Craft breweries with regular production, isobaric conical tanks. |
| Electronic Pneumatic (FCS / Cloud) | 0 to 2.5 bar (hundredth‑precision) / Tri‑Clamp | Total. Physical separation of sensor and discharge valve. | Breweries with automation, HACCP quality monitoring, fine profiling. |
Rolling Beers Technical Team Insight
Protect your pressure gauges from Krausen overflow! During vigorous fermentation (especially with highly attenuative yeasts or tanks filled to maximum capacity), foam can rise all the way to the spunding valve. If wort dries inside the mechanism or gauge, pressure readings become inaccurate and the valve may jam in the closed position. We recommend always placing a high degassing line (or a blow‑off/trap bottle) between the tank dome and your spunding valve, and regularly disinfecting the liquid in your airlock!