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Mixing Valves: Water Heaters

A Mixing valve, also known as a water heater mixing valve, is an electronically-controlled device that allows the user to preset the desired temperature of their domestic hot water. It can be thought of as two or three-way valves in one. Mixing valves are installed on both the cold and hot supply pipes at the point where they feed into your water heater. Mixing Valve installation is required by code for any area with more than six people; this will ensure proper disinfection of your system.

Mixing Valve Design

Mixing valves are simple in theory but somewhat complex when it comes to design and function. They consist of various moving parts which make them prone to wear over time if not inspected regularly, requiring replacement every few years (approximately five years). A Mixing valve uses a mechanism to control the flow of hot and cold water, thus allowing you to set your desired temperature. When you turn on a faucet in your house, either hot or cold, the Mixing valve redirects hot and cold through their respective pipes until it reaches a common mixing chamber. The Mixing chamber has a device called a thermostat that allows for the Mixing valves system to heat up or cool down based on your current needs. Mixing valves are always delivering water at the preset temperature, but by making adjustments to the lever, they can divert more or less hot water into said mixing chamber. Mixing valves come with safety features such as scald guards and pressure-reducing valves.


Mixing valves are also UL listed, meaning they have gone through rigorous safety testing. Mixing valves allow for the most accurate control over your hot water supply, allowing for versatile temperature changes that can be made instantly. Mixing valves ensure you do not accidentally scald yourself with too-hot water when taking a shower or filling up the bathtub. Mixing valves are commonly used in commercial buildings like schools, stadiums and office buildings where people come into contact with large volumes of water at once (e.g., cafeterias, locker rooms). Mixing valves control both cold and hot water separately to prepare it at the desired temperature for use by building occupants.

Installing a Mixing Valve

When installing Mixing Valves, set them between 120Ëš-140ËšF normally. Mixing valve settings can’t reliably stop scalding, so regular use of mixing valves or thermostatic Mixing valves in showers is not recommended because the temperature varies with the incoming water supply (which can vary widely during periods of high demand). Mixing valves do nothing to control pressure; adjusting them will make only a very small difference. Mixing valves should never be used on tub fillers or whirlpools where uncontrolled temperature changes are dangerous.

Mixing valves aren’t meant for controlling water flow (you can turn off both hot and cold), they’re for setting the temperature at each fixture individually. They cannot prevent hot water lines from freezing in an unheated area, either due to lack of insulation or related plumbing problems. Mixing valves can’t make cold water feed any hotter, either. Mixing valves will not prevent overheating of the boiler if it’s designed for that to happen – which most are. Mixing valves work fine with recirculation pumps and may help you save money on heating costs by limiting the temperature of incoming supply water.

Mixing faucets should be installed in multiple locations using separate shutoff valves at each location, allowing users to select the degree of temperature they prefer without over-pressurizing your system or requiring more heat from your hot water heater than is being used for showers and other uses throughout the house.

Mixing valve installation is required by code for any area with more than six people; if the building is multi-unit, that means you! Mixing valves allow for hot water to be set at 90ËšF or less. Mixing valves should never be used on bathtub fillers because of the risk of overheating and scalding. Mixing faucets may actually help save heating costs by allowing more control over the heating process, but won’t prevent frozen pipes in unheated areas or connected to uninsulated piping. Mixing valves are installed between the cold and hot supply lines at each fixture individually.

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