Mastering pressure dry hopping: The zero‑oxygen guide

What is the Hop Bong and why does it change everything?

The Hop Bong is a transparent technical‑polymer or stainless‑steel accessory that attaches to the top of your fermenter via a Tri‑Clamp fitting, right above a butterfly valve. It acts as a “safety airlock” (or decompression chamber) for your hop pellets.

The principle is simple: it allows you to introduce hops into the fermenter without ever exposing the beer to ambient air. Whether you own a stainless‑steel tank or a plastic fermenter, there are suitable solutions such as the universal Hop Bong Deluxe TC 1.5" kit or the Hop Bong pack for FermZilla lids.

The step‑by‑step protocol for successful pressure dry hopping

To reduce oxidation risk to nearly zero, you must follow a precise routine of pressure and gas‑flow management. Here’s how to proceed:

Step 1: Preparing the chamber

Make sure the large butterfly valve at the base of your Hop Bong is completely closed and airtight. Remove the top cap of the Hop Bong and pour in the required amount of hop pellets for your recipe. Replace the top cap and lock it with its Tri‑Clamp collar.

Step 2: Oxygen purge

At this stage, the Hop Bong tube contains your pellets — but also ambient air (and therefore oxygen). You must remove it:

• Connect your CO₂ cylinder to the grey Ball Lock gas post located on the side (or top, depending on the model) of the Hop Bong.
• Apply a light CO₂ pressure (around 0.5 BAR) into the tube.
• Briefly activate the small PRV (pressure relief valve) on the cap to let the gas escape.
• Repeat this pressurisation / venting cycle 3 to 4 times. CO₂, being heavier than air, will push the oxygen out and saturate the chamber. Your pellets are now in a 100% protective atmosphere.

Step 3: Pressure equalisation

If your beer is already fermenting or nearing the end of fermentation, your fermenter is under pressure (for example 1 BAR). If you open the butterfly valve immediately, the tank pressure will rush into the Hop Bong and blast your hops upward!

Before opening the valve, inject CO₂ into the Hop Bong until the chamber’s gauge shows exactly the same pressure as your fermenter. Both spaces are now perfectly balanced.

Step 4: The big drop

Open the lower butterfly valve fully and decisively. Under gravity, the pellets fall straight into the wort. Depending on the model, the passage diameter at the base of the tube may be 1.5" (about 38 mm). If you are performing a very large dry hop, hop pellets may sometimes clump together and create a small “plug” when opening. Simply open and close the butterfly valve firmly two or three times, or gently tap the transparent tube to create vibrations and help the hops fall through.

Step 5: Secure closure

Once all the hops have dropped (which you can easily verify thanks to the transparent tube), close the butterfly valve. You can then depressurise the Hop Bong via its top PRV for cleaning, while your beer continues its aromatic extraction in complete protection from air.

When should you perform pressure dry hopping?

Thanks to the Hop Bong, you are completely free with your timing:

• During active fermentation (Biotransformation): To obtain very fruity notes and allow yeast activity to integrate hop oils.
• At the end of fermentation: To maximise pure, “fresh” hop aroma without losing volatile compounds through an airlock.