The uninterrupted operation of any home heating equipment depends on many factors, including the correct choice of components, the characteristics of each of which determine the degree of efficiency and reliability of the heating system as a whole.

Warm water floors are modern equipment, the correct operation of which is also ensured by a number of devices that have a specific purpose.

In particular, maintaining the optimum temperature in the heated room is directly related to the intensity of the coolant supply to the water circuit, which is regulated by various types of valves. These control devices include a three-way valve for underfloor heating, without which a warm floor will not become a full-fledged functional system.

One of the models of the three-way valve

To get a superficial idea of ​​what kind of work a three-way mixing valve performs, and how significant its role is in a mixing unit, any scheme of warm water floors, regardless of the number and configuration of circuits, allows. For better orientation when choosing this device, let’s take a closer look at what this component is and what its principle of operation is.

The main function assigned to the three-way valve

The heating system «water heated floor» is fundamentally different from the traditionally used by us, radiator heating. The thing is that for heating circuits lying on the floor in the body of a concrete screed, a low coolant temperature is required. Underfloor heating is considered a low-temperature system, which is connected to heating devices or to a source of hot water through a mixing unit.

In order for heating to be carried out in accordance with sanitary standards, it is necessary to significantly reduce the temperature of the water coming from the heating source to the water circuits. It is this function that is assigned to the mixing unit, or, as it is commonly called among professionals, the mixing unit. Autonomous boiler in operating mode heats water up to the level of 950C. Slightly cooler is the water in the central heating system. For normal operation of heating floors, the optimum temperature of the coolant is 35-550C, which is obtained at the outlet of the mixer.

On a note: do not confuse the mixing unit with manifolds. The first is a set of various components and assemblies that provide regulation of the water supply to the water circuit, while the second is only an integral part of the entire control unit.

The mixing unit is a set of instruments and devices that perform their specific functions. If there is more or less enough information about the collector, but what a three-way valve is, few of us have an idea. The task of this device is to mix two liquid streams of different temperature. The cooled water coming from the return pipe and the hot water flowing through the pipe from the heating source, through the operation of this mechanism, are combined into one stream of the required temperature. The main part of this device is a temperature-sensitive core, an element that reacts to changes in the temperature of the aquatic environment, shrinking or expanding.

It is due to this design that the three-way valve works, aimed at automated control of the temperature of the coolant in the system.

On a note: this device is used not only in the operation of water heated floors, but also stands on the equipment of almost all autonomous heating systems operating on a liquid heat carrier.

The figure shows a diagram of a mixing unit for underfloor heating and the space occupied by a three-way valve.

Scheme of the mixing unit for underfloor heating and the location of the three-way valve in it.

Main design features and functions of the device


Having a rough idea of ​​\u200b\u200bthe principle of operation of a three-way valve, it is better to study the operation of this mechanism in detail. The name «three-way» determines the main function of the device — water of various origin enters the valve through two inlets:

  • hot coolant from a supply pipe connected to a heating device or to a riser of a central heating system;
  • cooled water returning after passing through the water circuit.

Mixing with each other in the valve in a certain proportion, the flows exit through the third branch pipe, having a given temperature value. The valve works constantly, since the principle of cyclic operation of underfloor heating is based on mixing hot water to the cooled coolant: heating — heat transfer — mixing — heat transfer — mixing.

The process of mixing two coolant flows of different temperatures must be constantly monitored, preferably in automatic mode. Otherwise, the intensity of heat exchange between the warm floor and the air in the room will not be tied to changes in the temperature in the room, and you will have to manually change the heating temperature of the coolant as necessary.

To carry out the admixture of the hot heat carrier in automatic mode, a temperature-sensitive head regulates the throughput of the valve depending on the temperatures of the mixed liquids in order to obtain a set value at the outlet.

Depending on the purpose and operating conditions, various types of three-way valves are used.

1. Heating systems

For a heating system with radiators powered by an autonomous boiler, the simplest type of device is used. Such three-way valves are inexpensive and have a relatively simple design, which allows them to be installed independently. The adjustment of the mixing volume in this case is carried out manually.

2. Hot water systems

In DHW systems, three-way valves are used to maintain safe water temperatures in the communications system, eliminating the possibility of burns. The design of such devices is also quite simple and understandable. Such devices differ from valves for heating systems by the presence of a special protective block that shuts off hot water in the absence of cold water in the water supply.

3. Warm water floors

Devices of this type are the most complex, as they are designed to maintain the desired temperature of the coolant in the heating circuits with reference to the air temperature in the room. The use of such devices in the mixing unit allows you to adjust the intensity of housing heating in automatic mode,

Important! The use of a three-way valve in the heating system requires the installation of a circulation pump — to maintain the pressure in the water circuit necessary for the correct operation of the mixing unit.

The layout of the mixing unit and the location of the three-way valve in it


Three-way valve model with adjustment scale

For underfloor heating, the tap is equipped with an adjusting handle and a measuring scale, with which the device is adjusted.

Options for using a three-way valve in underfloor heating systems

In small residential areas (bathroom or bathroom), heated floors are mounted without a mixing unit, which is not technically necessary. For the correct operation of the system, it is sufficient to use a three-way valve model with two shut-off valves.

On a note: a full-fledged mixing unit (with a pump, manifold, safety valves) costs a lot of money, and when equipping a heated floor in a bathroom, the cost of a mixing unit will exceed the cost of installing a water circuit by several times.

Such a device, due to the presence of a thermostat, will ensure the regulation of the temperature of the water entering the heating circuit.

In a heating system designed to heat the entire living area, a mixing unit with a three-way valve will be required without fail. Thermostatic three-way valves will guarantee an uninterrupted supply of treated water to all heating circuit loops.

Example: use for heating a living room in 20 m2 one water circuit of a significant length of heat pipes. Installing a control valve equipped with an electric drive on the supply pipe will allow, together with the pump, to ensure the necessary circulation of the coolant. This scheme involves the installation of a valve at the junction of the return pipe with the bypass. The operation of the thermostatic head is adjusted in such a way that at an excessively high temperature of the coolant, water circulates in a small circle.


Heating with underfloor heating living quarters in a house with two or more floors, involves the use of a large number of water circuits of different lengths. Accordingly, it will be necessary to install not one, but several mixing units.

In this case, a combination of a compatible three-way valve, a servo drive and a controller is used, which fixes the boundary parameters of the temperature of the coolant supplied to the water floor heating circuits. Warm water in this case will flow after the bundle immediately into a certain heated room, or go to the collector, after which it will be distributed through the heating pipes.

Valve selection and installation features

It is necessary to choose a valve model with reference to the characteristics of the heating system.

Today it is becoming fashionable to use three-way valves equipped with electric drives to equip mixing units, although the usual, traditional model is not much inferior to complex devices in terms of its technological characteristics. During the purchase, you should pay attention to the following nuances:

  • availability of technical documentation for the product (quality certificates, manufacturer’s warranty obligations, installation and operation instructions);
  • products made of brass or bronze are preferable — these metals interact well with hot water and have a low coefficient of thermal expansion.

On a note: when buying, you can determine the material from which the three-way valve is made by ordinary weighing. Take the device in your hand — if the product seems heavy enough, it is made of non-ferrous metal. Using faucets made of powdered composite materials by pressing means dooming yourself to unnecessary costs and trouble.

  • the connecting pipes of the selected valve model must match the parameters of the installation site — if the thread pitch is different from what you use when installing the mixing unit, the unit will not be able to be installed. The dimensions of the valves should be commensurate with the installation area of ​​underfloor heating — it is not advisable to install bulky units for heating a small area.


Installation of a three-way valve is not a difficult task, but requires compliance with technical rules. Typically, mixing valves are placed in front of the mixer on the supply pipe, at the connection points of the bypass and return pipe. The pump in the system is located behind the three-way valve.

After assembling the entire mixing unit, the reliability of the connections and the functionality of the valve are checked by a test run, based on the results of which, if necessary, commissioning is carried out.

A properly installed valve maintains the set temperature in the heated room and ensures rational flow of the coolant, and hence the efficiency of heating.


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