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BetterBottle® DryTrap™ Air Lock Information

Introduction - BetterBottle DryTraps cannot go dry.

The Problem

A pressure differential of just 0.005 bar (0.07 psi or 0.15 inches Hg) will lift a 5 cm (2") column of water and suck the liquid out of liquid-filled air locks and into a fermenter, potentially contaminating the wine or beer with oxygen and the liquid in the trap (e.g, moldy water, sodium bisulfite, vodka etc.). Pressure changes of that magnitude can be caused by a gust of wind, a temperature drop of a couple degrees, or moving a bottle. Evaporation is often blamed for the loss of liquid from a liquid-filled air lock, but pressure changes are the more likely cause. Liquid-filled air locks also extend about 10 cm (4") above the neck of a bottle, which can use up valuable self space.

The Solution

As the name implies, BetterBottle DryTrap air locks are not liquid-filled. They are precision check valves made of an incredibly tough, proprietary type of PET that can withstand continuous service at 100° C (212° F) and does not stain or take up flavors. A polished ceramic ball rests in a tapered seat to create a one-way seal. Gases can escape easily by pushing the ball up and off the seat, but they are blocked from flowing in the reverse direction. DryTraps extend less than 5 cm (2") above the top of BetterBottle carboys, so the bottles can easily slide onto shelves with a 56 cm (22") clearance and 4 levels of shelves can be installed against the wall in a room with a standard ceiling height.

Additional Information  

Use the popup menu associated with the DryTrap page for random access to all the specific information relating to BetterBottle carboys. For materials specifications, please refer to the Technical page.


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

  1. Remove the spring clip (4) and quick-disconnect hose barb adapter (1) and shake out the stainless steel retainer (2) and ceramic ball (3).
  2. To reassemble the Dry-Trap, 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 a DryTrap is installed and fermentation has slowed, the rate of carbon dioxide production can be easily monitored by connecting a hose to the outlet of the DryTrap and occasionally submerging the open end of the hose in container of water to make observations of 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 is non-porous and hydrophobic, making it extremely easy to clean and sanitize. Always rinse DryTraps thoroughly in clean water before storing them. BetterBottle is not aware of any detergents and sanitizers, used in home winemaking and beer brewing, that damage DryTraps when used according to their manufacturer's instructions. See the Technical page for specifics.

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

Part Numbers

1/2" DryTrap for Beter-Bottle O-ring closures or stoppers: BB-DRT(1/2)
Harmonized System Code:  3923.30.90.90 applies to these parts

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BetterBottle and DryTrap are trademarks of High-Q, Inc.