It’s the end of a hard work week and, as usual, you can’t wait to get home to do some brewing. With the time it all takes, nothing could be worse than losing a batch by contaminating it with unwanted wild yeast or bacteria.

Often contamination starts in the transition period between the boil and the pitching of yeast. Why? Within the boil all is safe, but once the wort gets below 170° F, all hell can break loose. There is a whole truckload of nasty stuff just waiting to get into your wort. The quicker you can pitch the yeast, the better.

For optimal activity, yeast should be pitched within 30 to 40 minutes after the end of the boil (for five-gallon batches). Preferably, the wort should begin active fermentation within 12 hours of the end of the boil. With proper chilling temperature and adequate starter volume, you could see fermentation in two or three hours. Because it is inevitable that you will have some amount of unwanted bacteria in your wort, the sooner fermentation commences the quicker the undesirables can be fought off. Therefore, it is advantageous to cool your wort as soon as possible.

Wort cooled too slowly, especially in periods over one hour, may not only become contaminated but may also develop a sweet, cooked corn-type aroma and flavor known as dimethyl sulfide (DMS). This is especially a problem with lighter kilned malts such as lager and pils.

The largest concern after boil should be to reduce the wort to pitching temperature in as little time as possible while maintaining sanitation. If you do not bother to cool your wort, you might as well not bother to sanitize your fermenter or hoses either.

A lot of brewers simply let their fermenter sit in cool water for hours on end or even overnight before pitching. Considering the average homebrewer’s pitching rate of about one to two ounces of yeast solution, your wort may sit an additional 24 hours before actual fermentation begins. That’s a long time to expose your brew to bacteria and other unwanted elements. You really should chill.

Chilling the brew is accomplished through a heat exchanger. Heat is energy, and energy has to go somewhere. With a heat exchanger you are simply transferring heat to another substance and carrying it away. In this case the other substance is water.

An ice cube provides a good example of heat exchange. If you sat an ice cube on your counter with your hand a few inches above it, you would feel the coolness. Notice that’s “coolness.” The ice cube is frozen, yet you do not feel the temperature at that degree. The reason is that the heat in the room is taking that frozen cube and carrying its temperature away. The cool air almost feels like it is blowing at your fingers.

There are many ways to cool your wort: the carboy in the bathtub trick, the carboy in the snow bank. But there are two types of cooling devices— counterflow and immersion—that make these unnecessary. Unlike the snow bank, you can use these all year. Also, you avoid the risk of shattering your glass carboy by putting hot wort into it—a full-fledged and dangerous disaster.

Immersion chilling is the act of immersing a cooling unit into hot wort, in this case a copper coil. Cold water flows through the copper then exits, carrying away the heat of the wort. This provides a fairly efficient method of cooling and is inexpensive to construct. Immersion chilling does have its downfalls; it can be quite slow, taking as long as 30 minutes. It also requires you to stir the wort at regular intervals of two or three minutes.

A counterflow chiller carries the wort within a copper tubing while cold water flows around the copper within a jacket in the opposite direction. The wort flows with the help of gravity, in one end and out the other, directly into the fermenter. The downfall is it requires much more attention to sanitation.

Most commercial breweries use a plate heat exchanger that is somewhat similar to the counterflow chiller. The hot wort flows into a vertical plate with worm-like trenches. Behind this plate is another plate that is almost identical yet contains the chilled water. These plates are sandwiched back to back throughout the unit. Each unit is generally expandable to accommodate more plates. Some units contain hundreds of plates.

Immersion Chiller
The simplest chiller for the homebrewer to construct is the immersion chiller; it equals much more than the sum of its parts.

You can build an immersion chiller and use it for years. Furthermore, if you later decide to change, it can become the inside coil of your counterflow chiller.

The Parts:

• 15 to 25 feet of 3/8-inch (outer diameter) soft copper tubing
• 10 feet of 3/8-inch (inner diameter) heavy-grade beverage-type plastic tubing (available at hardware or homebrew stores)
• 2 small hose clamps
• 1 female hose fitting (for faucet)

    
The copper tubing can be found at most home improvement or plumbing stores in coils of 25 to 50 feet. A reputable store can cut the length you need. This must be rolled into about 10-inch-diameter coils (or just less than the inside diameter of your kettle or fermenter). The copper can easily be bent around a paint can or plastic bucket. Leave at least a foot at the end and bend it to go up through the center of the coil for your outlet. Be very careful when making this bend. Without a tubing bender, it is very easy to crease the tubing at a 90-degree angle.

Attach half of the plastic tubing to one end and half to the other. On one end attach the female hose fitting for the input. Insert a six-inch length of 3/8-inch copper into the output end to act as a weight to keep this end in your drain.

(Note: You may want to substitute a brass fitting instead of the hose clamp to avoid any risk that the hose could soften and come off during the transfer of hot liquid.)

Putting It to Work
Using the immersion chiller is as easy as stirring your wort. Blow or rinse the dust off the coils and toss it into your boil during the last 10 minutes or so to sanitize it. Connect the input to your faucet, place the output into your sink, and you are ready to chill.

To achieve maximum effect, bounce the chiller while stirring it around within the wort. This will avoid hot or cold spots and cut down chilling time. This also will help aerate the wort—nothing like killing two beers with one stone.

Chilling may be done in the kettle or plastic fermenter. Chilling in the fermenter is advantageous considering you can transfer wort at 170° to 200° F, when it is much less vulnerable, and you really don’t need to sanitize your racking cane or tubing. However, you should never put hot wort into a glass fermenter.

A nice modification to the immersion chiller is to add a five- to 10-foot coil to the in-flow tube before the kettle. This additional coil can be submerged into a small bucket of ice to further chill the water before it enters the main chilling coil. This modification will reduce chilling time considerably.

Counterflow Chiller
The counterflow chiller is more efficient than the immersion chiller. However, it does require much more skill and effort to construct and sanitize. The construction requires proficiency at sweating copper joints.

The Parts:

• 20 to 30 feet of 3/8-inch (outer diameter) soft copper tubing (or more for 10-gallon batches or larger)
• 2 feet of 1/2-inch brass pipe
• 2 female brass T’s, 1/2-inch (sweat type)
• 2 compression fittings, 3/8-inch with 1/2-inch female ends (sweat type)
• 4 medium hose clamps
• 20 to 30 feet of 5/8-inch garden hose
• 5 feet of 3/8-inch (inner diameter) plastic tubing
• Lead-free solder
• Lead-free solder flux

The beauty of this chiller design is its fittings. They are like those commercially available yet can be constructed at home for a quarter of the cost.

The first thing you need to do is to insert the copper tubing into the garden hose. Cut equal amounts off both ends of the hose to achieve a hose length of 12 inches less than that of the copper tubing. Save the severed hose ends, as they will become your chilling water input and output. Carefully uncoil the copper tubing—be careful not to kink it—while inserting it into the hose. Continue insertion until equal amounts protrude from both ends. You may wish to do this outside unless you have a very long room in your house.

Next you want to coil the hose into roughly the same diameter it came in (about 12 to 15 inches), leaving about eight inches at the top and bottom uncoiled. To make it easy, do this around a five-gallon bucket.

Now make the fittings. With a hacksaw or pipe cutter, cut the copper pipe into four 2.5-inch lengths and two 1.5-inch lengths. The 2.5-inch lengths are used for the cold water input and output and the 1.5-inch lengths for the compression fitting connectors. Wire brush or sand with a plumbers cloth the inside of the brass T and the ends of the pipe lengths. Apply flux to the brushed or sanded parts and insert a 2.5-inch length to the T to form an L shape.

The 1.5-inch length goes onto the other end of the T to receive the compression fitting. Next, sweat one of the compression fittings on the 1.5-inch length. Repeat these steps for the other fitting.

The fittings are then slid over the copper tubing with one of the 2.5-inch lengths receiving the garden hose and secured with a hose clamp. The compression fitting is tightened around the brass tubing. This is done on both ends of the coil.

You now have one 2.5-inch length of each T open. The bottom of the coil is the output and the top the input. Insert the bottom remaining copper connection into the severed end of hose with the female hose connector that you earlier cut off. The other severed end with the male fitting goes to the fitting on the top of the coil. You now have a counterflow heat exchanger.

To use the counterflow chiller you will need a brass racking cane, since you will be siphoning boiling or near-boiling wort. One can be made simply with 3/8-inch (outer diameter) copper tubing bent into a cane shape at a height just taller than your brew kettle. Solder a 1/2-inch to 3/4-inch brass pipe cap to within 1/4-inch of the end of the cane for a trub dam.

Putting It to Work
Sanitizing the counterflow is a bittime consuming, but it can be accomplished. First, make up a typical sanitizing solution such as bleach or iodophore. You can siphon three to five gallons through the copper, then flush out with the same amount of hot tap water. While this will effectively sanitize a clean unit, it will not sanitize a dirty one. If you let the wort dry on after use, cleaning becomes very difficult and may even require pumping the cleaning solution through it.

To chill your wort attach 3/8-inch (inner diameter) plastic tubing to the racking cane with the other end attached to the input of the chiller. Attach another length to the output and into the fermenter. Attach the female hose connector to the faucet and place the male output into the sink. Turn on the water and start the siphon of wort into and through the chiller.

You will need some method of restricting the flow of wort into the chiller to set the heat exchange to the desired temperature. Clothespins work well as flow restrictors. The slower the wort travels through the copper, the cooler it will exit. Take its temperature as it exits and adjust the flow accordingly. Total chilling time should be approximately 20 minutes for five gallons.

After use, run boiling or very hot tap water throughout the copper followed by a light bleach or iodophore solution to clean.
    

Choose Your Method
Which chiller is for you? The immersion chiller works fine, even for batches as large at 10 gallons. But if you feel comfortable with the extra sanitizing efforts required and do occasional large batches, the counterflow may be just what you want.