Every time I travel I try to visit the local breweries and, if I can, do a brewery tour of each of the establishments. After touring a few breweries I found that every one does things a little bit differently in their proce-dures, but when it comes to the equipment there are definitely some standard tools of the trade. One of those tools that I have frequently seen used in microbreweries is the mixing valve.
As its name implies, a mixing valve is used to mix hot water and cold water to achieve a desired water temperature during the process. A mixing valve is very useful to achieve a precise temperature for mashing in or lautering, without the need for electronic temperature control. This column will explain the application and construction of a mixing valve for use at the homebrewing level.
Temperature control without electronic temperature controllers sometimes can be tedious even for preparing the water for a single infusion mash. The main problem is that the heaters always have some momentum to them and when turned off, the temperature continues to shoot up for some time. Water being hotter than needed is not a huge problem; it just means that we have to wait for it to cool down before mash in, or we have to add some "cold" water to the overheated water and mix.
Another homebrewing situation that is more difficult to control, even with electronic controllers, is maintaining constant temperature sparge water during lautering. In this process, water is drained from the hot liquor tank (HLT) and transferred to the lauter tun over the course of 30 minutes or so. Because this transfer time is fairly extended, you will find that you lose a significant amount of heat in the sparge water from the start to the finish of lautering. Adjusting the temperature would usually require a stoppage in draining water out of the HLT too, but the lautering process works best if done slowly and continuously, so this is not an attractive solution.
This is where a mixing valve comes in handy. To keep a constant temperature using a mixing valve, you would intentionally overheat the water in the HLT by 15–20 °F (8–11 °C) and while this water is being transferred into the mash lauter tun some "cold" (room temperature water) is injected in line to achieve your target temperature. In the case of the lautering process, where significant temperature losses may be expected due to the long transfer time, it is very easy to make adjustments to the amount of "cold" water injected so that the water temperature remains constant through the entire process. As the hot water cools, you simply reduce the rate of flow of the cooler water to limit the cooling effect it has.
Parts and Materials
(1) 1⁄4-inch needle valve (McMaster-Carr Part #46425K12)
(2) 1⁄4-inch threaded tees
(2) 1⁄4-inch x close nipples
(1) 1⁄4-inch x 3-inch nipple
(1) 1⁄4-inch ball valve (flow throttling valve)
(1) 1⁄4 MPT x 3⁄8-inch barb adapter
1 Bi-metal thermometer with 1⁄4-inch thread for installation
Teflon threading tape
Build the Mixing Valve
1. Assemble Needle Valve Connections
Thread 1⁄4-inch x 1⁄4-inch barb and 1⁄4-inch close nipple into needle valve as shown. The needle valve used in this project is directional so the fittings must be installed according to the direction of water flow (barb fitting to the left of arrow and threaded close nipple to the right side of the arrow). One nice feature of this needle valve is that the handle threads are color coded providing a visual reference point for repeated settings (one full turn per color).
2. Assemble Mixing Valve Lower Body
Assemble mixing valve lower body as shown. The needle valve side will receive cold water (tap water). The 3⁄8-inch barb fitting will receive hot water. Teflon threading tape should be applied on threads to get a good seal.
3. Assemble Remaining Parts
Assemble the remaining parts of the mixing valve upper body as shown. It is very important that the thermometer is installed in a vertical position to assure the thermometer is fully immersed in water for an accurate measurement. The main components of the mixing valve as shown in the picture are:
1. Needle valve is used to meter cold water injection.
2. Hot water inlet port (receives from hot liquor tank (HLT)).
3. Thermometer for indication of blended water temperature.
4. Throttling valve is used to adjust the flow rate going out of mixing valve.
Once the mixing valve construction has been completed, it is ready for installation into your homebrewing system. A 1⁄4-inch ID hose is recommended for plumbing cold water to the mixing valve, and a 3⁄8-inch ID hose is recommended for plumbing hot water to the mixing valve from HLT. Use clamps for securing the hoses to the mixing valve. A final recommendation is to practice the temperature adjusting process until you become comfortable with the tweaking of valves and its response in temperature.
Use the Mixing Valve
1. Heat Sparge Water
Heat up sparge water in HLT approximately 20 °F (11 °C) higher than your desired set point (more or less depending on cooling losses expected). For example, if you want your sparge water to be 168 °F (76 °C), then you would heat up your water close to 190 °F (88 °C). Overheating the sparge water allows you to maintain a constant temperature throughout the lautering process by cooling it down by adjusting the cold water inlet at the needle valve.
2. Pump Sparge Water Into Lauter Tun
Throttle the outlet valve of mixing valve to the approximate desired flow rate. Start pumping sparge water from HLT into lauter tun. Make any adjustments to the total water flow rate.
3. Adjust Cold Water Flow
Adjust injection of cold water (room temperature water) until desired temperature is shown in thermometer located at outlet of mixing valve. Monitor the temperature of the sparge water at the outlet of mixing valve, and make small adjustments as necessary throughout the lautering process.