DryTrap™ Air Lock


A BetterBottle DryTrap™ is a dry air trap, or air lock. It is a precision check valve made of an incredibly tough, proprietary PET that does not stain or impart flavors and is easily cleaned and sanitized. A polished glass/ceramic ball rests in a precision tapered seat to create a one-way seal. Fermentation gases can escape easily by pushing the ball up, but air is blocked from flowing in the reverse direction. A DryTrap has many advantages compared to liquid-filled air locks.

Additional Information - Use the popup menus associated with the DryTrap and How-To Tips tabs at the left side for random access to all the specific information relating to the Drytrap. Scrolling down this page will access the DryTrap specific information in sequential fashion.

Chemical Resistance - In general, avoid very strong caustics, such as KOH and NaOH (lyes), and concentrated aliphatic ketones (e.g., essence oils). For additional materials specifications, please refer to the Technical tab at the top of this page.

DryTraps Do Not Dry Out Or Suck Back

DryTrap air locks do not use liquid, so there is nothing to suck back, blow out, or evaporate. Evaporation is often blamed for the loss of liquid from a liquid-filled air lock, but pressure changes are also a likely cause. A pressure differential of 0.005 bar (0.07 psi or 0.15 inches Hg) is all it takes to lift a 5 cm (2") column of water and suck the liquid out of liquid-filled air locks and into fermenters, contaminating the wine or beer with the liquid in the trap and letting in oxygen. Is it any wonder so many winemakers and brewers use vodka to fill their liquid-filled air locks in order to prevent mold and bacterial growth rather than solutions of biocides, such as sodium bisulfite.

DryTraps Block Oxygen Entry More Effectively

Oxygen can move through water - fish and plants live in water. Oxygen can also permeate through plastics such as polystyrene hundreds of times more rapidly than through PET. Utilizing new technology, which accurately measures trace concentrations of oxygen in closed spaces, BetterBottle engineers determined that DryTrap air locks are more effective at blocking the passage of oxygen than conventional water-filled air locks.

Click HERE to view the study (1.5Mb PDF).

DryTraps Save Space

A DryTrap only stands 3.6 cm (1.4") above the top of a closure. BetterBottle carboys fitted with DryTraps and BetterBottle O-ring Closures are only about 53.5 cm (21") tall. This means that BetterBottle carboys will fit into many small refrigerators and they can be conveniently placed on 4-high shelves.


BetterBottle DryTraps simply plug into a BetterBottle O-ring closures as well as standard stoppers and DryTraps are easy to clean and reassemble.

To disassemble a DryTrap, remove the stainless-steel spring clip (4) and quick-disconnect hose barb adapter (1) and shake out the stainless-steel retainer (2) and ceramic ball (3). To remove the O-ring from the hose adapter (1) hold the part in one hand with your thumb nail across the O-ring to keep it from moving in the groove, while you push a wave of the O-ring toward your nail to make a bulge that you can roll out of the groove. Use only BetterBottle O-rings for replacement; they are made of special materials that cannot be easily obtained through hardware suppliers and other materials may not function correctly.

To reassemble the DryTrap, check that the tapered seat and ceramic ball (3) are clean. Drop the ball into the seat and install the stainless steel retainer (2) on the shoulder above the ball. If the retainer is not in place, the ball could bounce up to the opening in the hose barb and prevent outflow. Install the quick-disconnect hose barb adapter (1) and lock it in place with the clip (2). Confirm that the ball rattles in the seat.
DryTraps should not be installed until foaming has settled away from the neck of a carboy. Prior to that point, the rate at which carbon dioxide is being produced should be so rapid that a blow hose will suffice. Once fermentation has slowed and a DryTrap is installed, the rate of carbon dioxide production can be easily monitored by listening to the gentle clicking of the valve as it opens and closes. Alternatively, a hose can be connected to the outlet of the DryTrap and the free end occasionally submerged in container of water to observe the rate of bubbling. To quickly assess the fermentation rate in large numbers of bottles at a glance, consider hanging a zipper, sandwich bag, filled with some water, on each dry trap. Pierce a hole through the edge of a bag, just below the zipper and push the outlet of the DryTraps through the hole. The zipper makes it easy to position, fill, and close a bag.

Cleaning / Sanitizing
The special PET from which BetterBottle DryTraps are made has a non-porous, hydrophobic surface, making it extremely easy to clean and sanitize. DryTraps may be damaged by temperatures exceeding 75° C (167° F). Read the Wash/Sanitize section, under the Technical tab at the top of this page, for important information. The PET is very tough and will not scratch easily, but take precautions not to scratch the precision tapered seat in the body of the DryTrap. Always rinse DryTraps thoroughly in clean water before storing them.

Abrasive scouring pads and cleansers should never be required or used.

Soaking metal parts in cleaning or sanitizing solutions can cause corrosion - they should be removed.

It should not be necessary to remove the O-ring for cleaning and sanitation. If the O-ring requires replacement for any reason, do not use sharp tools to remove it; pin one side of the O-ring into its groove with a finger nail and use the other hand to rub the rest of the O-ring so that it bulges up in front of the pinch point and can be rolled out of the groove. Use only BetterBottle O-rings, balls, retainers, and clips for replacement; they are made of special materials that cannot be easily obtained through hardware suppliers and other materials will not function correctly.

Part Numbers
1/2" DryTrap™ for BetterBottle O-ring closures or stoppers - BB-DRT4
  • Replacement set of O-ring, ball, retainer, and clip for 1/2" DryTrap - BB-DRT4-SERV

  • Packaging
    Harmonized System Code - 3923.30.90.90 applies to these parts

    BB-DRT4 -
    Individually packed in a hang-hole, zipper bag
    Bags of 20 individual packages - 0.66 lbs (0.30 Kg)