Hydraulic heating systems used today in everyday life are a convenient and efficient heating option. Despite the relatively simple and understandable principle of operation, such systems are distinguished by a large set of components, devices and mechanisms that ensure the functionality of heating equipment. For a warm floor that you plan to equip at home or in an apartment, you cannot do without special shut-off valves.

One of the most common and well-known mechanisms used in underfloor heating systems are mixing taps and valves. The devices perform one of the main functions, adjusting the supply of coolant in the system. The three-way faucet used for underfloor heating plays a key role in this regard. Without it, it is difficult to imagine the normal operation of warm water floors, especially when it comes to a full-fledged home heating system. Water floors used in practice can have a simple and complex design. A simple heating circuit is usually equipped with manually operated mechanical mixing devices. Let us consider in more detail what a three-way valve is, the principle of operation of this device and design features.

Scope of use of the crane

If it is unimportant for you which heating system will be equipped in your home, try to use the simplest, most reliable and proven mechanisms and components. The three-way valve, since its inception, has become one of the most common types of valves. The device is designed in such a way that by means of simple and uncomplicated mechanical manipulations, the water flow can be adjusted.

Important! It should be understood that underfloor heating is a low-temperature heating system. The maximum allowable heating temperature parameters for operation 35-550C. Heating sources heat water up to 75-950C. Installation of a three-way valve provides a mixture of hot and cold water, for the subsequent supply of prepared water to the water circuit of underfloor heating.

By installing such a valve in the piping system, you get the opportunity, by switching, to independently distribute the direction and intensity of the coolant flows, mixing cold water with a hot stream. The name of the crane was due to the principle of operation. The device performs the main work, having three switching points, combining two water streams into a third one. In appearance, the faucet is an ordinary tee, equipped inside with a locking or regulating mechanism. It locates the device in front of the mixing unit, at the place where the bypass is connected to the main supply pipe.

Typically, a three-way valve is used in an underfloor heating system to increase the efficiency of the heating circuit. The operation of the device provides, as mentioned earlier, mixing water of different temperatures into a single stream. Such adjustment creates the necessary temperature conditions in the heated room and provides significant energy savings during the operation of heating devices.

Design features and principle of operation of the crane

The need for mixing and distribution of water flow at first glance is simple and understandable. However, not everyone understands how the desired effect can be achieved. To do this, consider the principle of operation of a three-way valve and its design. For a better idea, consider the internal structure of the crane in different modes of operation.

The following diagrams show step by step switching of the crane:

  • Position one: the valve closes the second branch pipe, the main flow is supplied from the third branch pipe in the direction of the first branch pipe. Cold water circulates in the system.
  • Position two: the third flow is closed (usually bypass) and the main flow of hot water follows from the second branch pipe towards the first.
  • Third position: the movable damper is placed in the middle position between the second and third nozzles. In this position, cold water from the third pipe is mixed with hot water from the second. Further, the flow is directed to the first branch pipe.


Thanks to the drawings, the principle of operation of the valve becomes clear, how water passes through the device and how cold water is mixed with hot liquid.

For a better understanding, consider an example: The temperature of the heat carrier supplied from the central heating system is 700C. For underfloor heating installed in the room, you need to have water at a temperature of 35-550C. It is technically impossible to reduce the heating temperature of the water circulating in the central heating riser or coming from the heater. What is done in such situations?

A three-way mixing valve will help solve the technological problem. The device built into the pipeline will create technological possibilities for mixing cool water coming in the opposite direction from the water circuit with the main hot water flow. How it’s done?

The flag of the movable damper is located in the middle position, between the second and third inlets of the crane. As a result, return water with a temperature of 200C is mixed with hot water coming from a heating source with a temperature of 700C. At the outlet, prepared water is already flowing into the first pipe for a warm floor at the optimum temperature.

In a similar way, the temperature of the coolant consumed for the operation of several water circuits is adjusted.

Working according to this scheme, a three-way valve has an appropriate design. The product is usually made of durable metal alloys, brass or bronze. The main body is a one-piece cast structure with three inlets. Two branch pipes provide the supply of cold and hot water, but the third, outlet pipe is used to supply the working fluid for heating circuits.

The locking mechanism in the tap can be of three types:

  • conical;
  • cylindrical;
  • ball.

The regulation of the flow intensity and direction is carried out by the rod, a part of the mechanism that moves in a vertical position and sets the locking element in motion. In most models, in particular those whose device is shown in the figures, a ball valve is used that rotates around its axis. Cylindrical and conical dampers are less commonly used.

On a note: ball dampers provide the most hermetic overlap of the nozzles, in contrast to the stem, which is only engaged in the redistribution of flows. The best option would be to use faucet models that have two functions at once: shut-off and distribution.

In terms of manufacturability, both types of shut-off and distribution valve are capable of both mixing and distributing flows. In practice, it turns out that the three-way shut-off valve is more difficult to cope with the mixing mode. Such products are usually equipped with ball or cylindrical valves. In the case of regulating (distributing) taps, the situation is different. The stem moves with manual control or can be controlled automatically by a thermal head (in the case of a three-way valve). Such valves are much more reliable, since with a significant pressure surge in the pipeline, the stem is able to withstand hydraulic shock.

When buying a three-way valve, you should pay attention to the technical parameters of the devices:

  • material of manufacture;
  • maximum operating temperature of the coolant (usually up to 1200);
  • nominal working pressure PN in the range of 10-16 kgf/cm2;
  • nominal bore 15-40 mm.

Important! If the crane is used incorrectly, the mechanism may jam. Don’t buy cheap devices. Rapid wear of the movable structural elements will lead to loss of tightness of the assembly. Modern powder alloys used to make plumbing fixtures are weakly resistant to corrosion and may not withstand water hammer.

Distribution valves are installed for piping heating systems using heating boilers complete with storage boilers. Externally, both types, and the mixing and distributing taps are the same. The only difference is the mode of operation. It can be hydraulic mode variable or constant.

A three-way bypass valve with a constant mode is used in everyday life when there is a circulating coolant of constant volume. Variable hydraulic mode is suitable for heating systems where mixing is carried out depending on the volume of the heat carrier used.

Installation of a three-way valve


Products are installed on the main supply pipe in front of the circulating pump and mixing units. The cast structure of the crane is attached using couplings, flanges or by welding (when using a metal pipeline).

The following types of devices are commonly used in the heating system:

  • G, T and S — figurative, depending on the form of rotation;
  • according to the method of landing the shutter mechanism — stuffing box or tension valves;
  • according to the type of the flow part, the valves are trial-through and full-bore.

The operation of the device can be controlled manually. As a rule, this method of control is the cheapest and most common. The operation of a three-way valve in this case is similar to the operation of a ball valve. Devices equipped with a thermal head and an electric drive are mounted in heating systems designed for heating large areas and requiring continuous operation. We are already talking about the technological improvement of a conventional valve into a more technologically advanced device — a three-way valve.

The model of cranes equipped with a pneumatic drive is considered to be common. This type of device is safe, unlike an electromechanical device.

Differences between a three-way valve and a three-way valve


When starting to install a warm floor, few of us feel the difference between a three-way faucet and a valve of a similar design. If you want to equip a simple and fairly cheap heating system, give preference to a conventional valve. If, on the contrary, you have conceived a large-scale design, full-fledged heating of residential premises due to underfloor heating, it is better to give preference to a three-way valve. There is no significant difference between the two devices. The difference is only in the control options. The three-way valve is operated manually, while the valve, a more technically complex device, is designed for automatic operation.

The change in the position of the shutter damper in an automated device is carried out due to the operation of an electromechanical device. Working with manual valves, you adjust the flows on a whim, independently determining whether it is cold in the room or warm, increasing or decreasing the intensity of the flow of hot water in the water floor loops.

The three-way valve interacts with a thermostat that controls the temperature in the room. To exceed or decrease the specified temperature parameters, the thermal head of the device reacts, actuating the shutter rod. Due to the installation of three-way valves in the heating system «warm floors», it is possible not only to achieve the required temperature regime, but also to optimize the operation of all heating circuits.

According to the principle of operation of the valve, there are usually mixing and distributing.


When installing underfloor heating, you can not do without the use of a three-way valve. It is up to you to give preference to a mechanical product or to put an automated device, a three-way valve on the pipeline.

When installing a mixing unit and direct distribution taps, it is better to use the experience and knowledge of specialists. Errors made during installation can cause a violation of the circulation of the coolant in the system and subsequently cause mechanical damage to the underfloor heating pipeline. Despite the fact that the design of bypass valves has been tested by time, the rules and instructions should be followed during the operation of the products, extending the shelf life of the devices.


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