Bubbler Assembly

A bubbler air lock is necessary for the proper operation of the BeerBotz gas meters. The Honeywell™ AWM-type gas meters that are used are permenenantly damaged if a liquid (or fermentation foam) is run through them. These meters have been found to provide years of reliable service while protected from fermentation blow-off by an appropriate bubbler.

Five Gallon Setup

The goal is to stop all of the possible foam in the bubbler. Fermenter space is valuable, so a common practice is to fill the fermenter full and not worry about whatever foam comes out. The foam will fill up and run out of the blow-off bucket. The amount of foam produced would be determined by the temperature and starting gravity of the particular batch.

After running the equipment for a while, a brewer will know what to expect with respect to the amount of blow-off a certain batch will produce. The new thing here is to determine the measures needed to make sure the foam does not get out of the bubbler/air lock. You can use a combination of the following strategies:

  • Leave head space in the top of the fermenter.
  • Use a large bubbler (so the foam breaks by the time it exits at the top)
  • Use a heavy dose of antifoam in the bubbler. If antifoam is used in the correct concentration (or greater), it crashes all of the foam in the bubbler.

The best way to begin is to first set up your bubbler without the meter attached and do a couple test batches. Another safe way to start would be to only use the meter when you are doing lagers, which may not blow off any foam at all. The size of the tubing to use is probably already determined... you are probably already running tubing into a blow-off bucket.

In summary, the amount of blow-off is predictable given the batch style. With this knowledge the correct measures can be put in place to contain the foam and protect the gas meter from liquid damage.

Large Bubbler Assembly (for 1-inch Tubing From Fermenter)

Fashioning a large bubbler from a plastic carboy is quite easy. All you need is the carboy, one inch tubing bulkheads, and some 7/8ths inch tubing. The bulkheads are installed on to the carboy by cutting a hole with a hole saw. (see video: Small Bubbler Assembly)

Mark center... and drill hole

You should select a carboy that has two flat spots on the top for the bulkheads. Some examples are:

5 gallon F-style jug (also called: Hedpack)
15 gallon plastic drum

The best bulkheads I have found so far are designed for hydroponic systems. Look for: Botanicare Ebb & Flow Barbed Fitting - 1" Bulkhead

Repeat for second bulkhead

These bulkheads only have a 1" tubing barb on one side. For the side that reaches down to the air lock water, you will need a: 3/4" NPT x 1" Hose ID Black HDPE Adapter. Home Depot carries these: (Watts Nylon Hose Barb; 1 in ID x x 3/4 in MIP; A-625 (White)). Use teflon thread tape when you mount this on the bulkhead.

The large size gas meter (AWM720P1) requires a tubing size a little smaller than one inch. Use 7/8" (Tygon beverage tube; part #: AAB00059:7/8" (0.875)). With this size tubing, the gas meter slips on and off easily (which is what you want). This tubing can be slipped on to the 1" bulkhead hose barb, but you need to soak the tubing in hot water first.

Make tube for "In" side (tube has to reach the bottom)

You need to drill a clean hole in the plastic so the rubber gasket of the bulkhead can provide an air-tight seal. Use a very sharp hole saw (eg. Starrett 1 3/8" carbide tipped hope saw CT138; Arbor Type: A2 or A10). Also, taping the plastic with painters tape before drilling helps to achieve a clean hole. After drilling, clear the plastic strings off of the hole edges with a razor blade.

Once both holes are drilled and cleaned, fashion the "In" side bulkhead such that the tube reaches to the bottom of the carboy. Mount the bulkheads, and label the "In" and "Out" with a permanent marker.

Mount bulkheads and label "In" and "Out" with a marker

Notes on use: The gas meter manufacturer recommends that the tubing run just before the meter is straight/linear for a couple of feet. I have found this to be an issue only at ~>50% of the full flow of the meter (for the 720P, systems greater than 30 barrels). What is happening here is that, at large flows, the flow of the gas inside the tube has a dead spot on the interior side of a curve in the tube. If the flow is not even through the meter, the meter will not provide accurate readings. From previous observation, this effect is accompanied by a sound being generated by the gas exiting the tube. It could be a whine or a howl. If you ever hear any noise from the exit tubing, you can bet that the meter will not be giving accurate results. Adjust your system to provide a linear tubing run before the meter to fix this.