Why is a bypass needed in heating systems? Bypass: what is it and how to install it? Bypass valve in the heating system

17.10.2023

Anyone who has had even a little experience with utility networks is probably familiar with the term “bypass”. In simple words, this is a bypass line through which water can flow due to various circumstances. In the article we will consider these circumstances and understand what role the bypass plays in the heating and water supply system. We will also show you how to install it correctly with your own hands if necessary.

Bypass functions in the heating system

Let us clarify that a bypass is a pipeline designed to allow water to flow bypassing a certain section of the main line where some equipment is installed. In heating circuits it can be found in two places:

in single-pipe systems as a jumper on radiators;
on the distribution manifold of water heated floors.

As you know, in a one-pipe heating system, the heat transfer of the first battery affects the operation of the next one, and so on. This applies to both vertical and horizontal layouts. If a bypass is not installed in the heating system, the radiators will be switched on in series. As a result, the first of them will take the maximum amount of heat, the second will take all that is left, and the third will receive only the cooled coolant.

To prevent this from happening, the supply and return near each battery are connected by a jumper, whose task is to direct part of the coolant bypassing the radiator. In this case, the principle of operation of the bypass is to transfer the same part of the heat to near and far heating devices and reduce their dependence on each other. How this is implemented can be seen in the figure:

Important. In the vertical system shown, the bypass device is provided so that the diameter of the pipe is smaller than the main line and slightly offset from its axis to the side. The goal is to prevent the coolant from passing in a straight line under the influence of gravity, past the radiator. In a horizontal system, the main pipe itself is a bypass, while it does not shift anywhere and remains the same flow area everywhere.

In a heating system, a bypass is needed to distribute heat evenly across the radiators, as well as to perform their repair or maintenance. If for some reason you need to disconnect and remove the heating device, then simply turn off the 2 taps installed at the coolant inlet and outlet. Then the water will follow a bypass path through the jumper.

But the heating bypass on the water heated floor manifold plays a different role. Here the bypass line is part of a mixing unit with a three-way valve. The task of the unit is to prepare the coolant at the required temperature for supply to the heating circuits of underfloor heating. Indeed, in these circuits the water temperature does not exceed 45 ºС, while in the supply line it can be 80 ºС.

In normal mode, the three-way valve allows hot water from the system to reach the heated floor in a limited amount. The rest of the coolant passes through this automatic bypass, mixes with cold water from the collector and returns back to the boiler. Since the temperature difference in the main and collector is significant, the bypass line is used constantly. It turns out that without it, normal functioning of underfloor heating is impossible.

Bypass in the boiler room

In boiler piping schemes, a bypass line is also necessary in 2 cases:

as a bypass for a circulation pump;
for organizing a small circulation circuit for a solid fuel boiler.

A pump installed on a bypass pipeline is found in heating systems quite often, sometimes even without special need. The fact is that a one-pipe or two-pipe heating system, originally designed with forced circulation, will never be able to function when the pump is turned off. It does not have large slopes and increased pipe diameters for this. But a bypass for the pump is precisely what is needed so that water can flow in a straight line while the pumping device is not working.

Hence the conclusion: when connecting a system designed for forced circulation to a boiler, there is no need to install the pump on the bypass. Disabling and removing the unit will in any case stop the movement of the coolant, so the pump is installed in a straight line.

Another thing is a system adapted to the natural movement of water. It often happens that in order to increase efficiency, a pump is not simply built into it, but a bypass system with a check valve is installed in the direct line. This allows you to automatically switch to natural circulation in the event of a power outage, which is reflected in the diagram:

While the pump is running, it presses the valve on the reverse side with its pressure and does not allow flow to flow in a straight line. As soon as you turn off the power or turn off one of the taps, the pressure will disappear and the bypass valve will open a direct path for the coolant, convective movement of water will be restored. You can safely remove the pump or clean the sump; this will not disrupt the operation of the system, it will simply switch to a different mode.

Well, the last place to use the bypass is the small circulation circuit of a solid fuel boiler with a mixing unit. Here, a jumper connected to a three-way valve allows the heat generator to warm up to a temperature of 50 ºC in order to avoid the effects of low-temperature corrosion on the steel walls of the firebox. In this case, the bypass circuit looks like this:

The principle of operation is simple: the valve does not allow cold water from the system into the boiler until the coolant circulating through the bypass line heats up to the required temperature. Then the valve opens and lets cold water into the circuit, mixing it with hot water. Then condensation does not form on the walls of the firebox and corrosion does not occur.

Sometimes a bypass is still needed in the water supply system. For example, to remove a heated towel rail in the bathroom for repair, cleaning or replacement. Since it is connected to the hot water riser, its dismantling in an apartment building will create a lot of inconvenience. It’s easier to foresee this in advance and install a jumper with a tap when installing the heater.

How to install the bypass correctly

The distribution unit for underfloor heating also includes a bypass line, but this is a topic for another discussion. As for jumpers on a one-pipe system, their installation is very simple and is carried out during the installation of the system, since without them the latter will not work correctly. It is not much more difficult to install a bypass line with a circulation pump yourself. It is enough to have a regular set of tools and study the diagram:

Advice. In order not to collect all the parts separately, you can buy a ready-made assembly, shown in the figure below:

Installing a bypass for a heated towel rail is also not difficult. For connections, you can take metal-plastic pipes, and also purchase taps, tees and bends. Perform assembly in accordance with the diagram:

Conclusion

It turns out that a simple piece of pipe, which is a bypass line, can play an important role in many cases. Here it ensures the operation of the system, there it helps distribute heat, and sometimes protects the equipment. In all of the above cases, you cannot do without a bypass.

Surely each of us has come across the above term. In this article we will answer the following questions:

"What is bypass"?
“What is a bypass for?”
“How is a bypass installed?”
“Automatic bypass - what is it?”

The general meaning of the word is very vague and imprecise, so when you use this term in your speech, it is necessary to clarify the scope and principle of operation.

Bypass Application Areas

In the first case, the device is used in a water supply system. As a rule, this device is used either when installing a circulation pump, the purpose of the latter is to increase the pressure in the system (in this case, installing the device yourself is mandatory), or when installing all kinds of meters and other metering devices. The valve performs only one function - it is a bypass line.
Bypass in a water heating system – this is a special device, which allows you to adjust the water supply to the radiator batteries with very high precision. A lot depends on this detail. Each of us hates to be in a room where it is either too cold or too hot. The valve, in turn, solves this significant problem, making your stay in the room comfortable and pleasant. The device creates a pleasant microclimate and avoids sudden temperature changes.

Bypass device and principle of its operation

The simplest part of this structural system is a small piece of pipe in the form of a jumper. However, a full-fledged valve must have at least three taps for water supply, since if at least one of them is missing, the device will not be able to work as intended. This device is installed between the direct and return wiring of a conventional heating radiator.

Bypass types

So, it should immediately be noted that all models of this device, according to their characteristics, can be divided into two large groups. Each of them has its own characteristics, which will significantly affect the operating principle of radiator batteries or water supply system.

The first group includes devices with a check valve. As a rule, such devices are used for circulation pumps. This bypass does not work all the time, but when necessary. The operation occurs as follows: after turning on the pump, the valve automatically opens due to excess pressure, and then begins to let in hot water. water or other heat carrier. After the pump has finished operating, the bypass also automatically stops working. However, you should be careful: if rust gets in, the device may fail.
The second type includes devices without a valve. This type will ensure reconstruction or repair without shutting down the entire heating system.

Do-it-yourself bypass installation

Do-it-yourself installation of such a device as a bypass is a very simple process; it does not require much experience from you and a wide range of tools - it is enough to have only a basic kit.

It is impossible to feel comfortable even in a very beautifully decorated house if it is cold. Therefore, the first priority of any homeowner is to install an effective heating system. Moreover, it must ensure the creation of a pleasant microclimate in the premises, since the situation when “you can’t breathe” from the heat is no less unpleasant than the cold in the house. A way to avoid all these heating “extremes” has been invented for a very long time. Engineers have developed such a simple but very practical device as a bypass in the heating system. It is with its help that you can very accurately regulate the supply of coolant to radiator batteries if we are talking about a water heating system.

What is bypass?

Probably every self-respecting heating system installer must explain to clients what a bypass is from the point of view of the common man. And, as you know, repetition is the mother of learning, so we will literally describe this important structural element of the heating system in a nutshell.

A bypass is a jumper in the form of a piece of pipe that is installed between the direct and return wiring of a conventional heating radiator. The transverse diameter of the bypass should be one caliber less than the diameter of the supply pipes. As a rule, a half-inch pipe is used to install a bypass.

Such a bypass can be bought at any store, and inexpensively.

Examples of using bypass

Example #1 - adjusting the coolant

The functional purpose of the bypass is to return excess coolant from the heating battery to the riser when its quantity changes using a manual or automatic thermostat. In other words, the coolant is transported through the bypass parallel to the shut-off and control valves. Without this element, it is impossible to repair the battery when the heating system is in working order. The bypass also speeds up the process of filling or emptying the system.

This is how a bypass can be introduced into a heating system

Example #2 - system operation without electricity

Installation of a bypass in a heating system is especially relevant when installing modern heating systems that involve the use. People who are faced with heating installation for the first time often ask the craftsmen or consultants in stores: “How will the system work if the electricity goes out?” After all, everyone is accustomed to the fact that the standard floor-standing boiler used in the past was not connected to electricity. And equipping the heating system with a circulation pump makes it energy-dependent.

That's exactly where the bypass comes to the rescue in such situations. Its role in this case is very simple - at the moment of a power outage in the network, the consumer must turn off the coolant supply taps to the pump and open the tap on the central pipe. By the way, this can happen automatically if a bypass with a valve is used. These simple manipulations switch the heating system to natural circulation mode.

Installation of devices on the bypass should be carried out towards the coolant in the following sequence:

filter;
check valve;
circulation pump.

It is important to note that the introduction of a bypass into the riser near the circulation pump must be carried out using shut-off valves. It is better to install the element itself horizontally. In this case, the system will be protected from air accumulation.

Example #3 - resuscitation of single-pipe heating

Yes, the single-pipe heating system is obsolete today, but it can still be found quite often in Soviet-built buildings. Moreover, there are such miracles when such heating functions very efficiently even in apartments in winter, it’s simply hot. Installing a bypass will also help correct the situation. In principle, there is nothing complicated in this work, but it is still worth meeting some conditions:

The bypass should be located at the maximum distance from the vertical section of the pipe, that is, as close to the battery as possible.
The bypass pipe can be made directly at the installation site - a pipe, a tee and welding work will be required. Or you can purchase such an element ready-made and install it on threaded connections.
The radiator inlet and bypass must be separated by a control valve or radiator thermostat.

By installing such a device, you will get a banal “temperature regulator in the house.”

The influence of the bypass pipe on energy costs

Installing a bypass will definitely have a positive effect on reducing energy costs. If we compare the operation of a heating system with the use of a closing section and a conventional flow one, then the first will be characterized by a decrease in the volume of coolant supplied to the battery by 30-35%. This means that the heat transfer from the radiator will decrease by up to 10%.

In practice, these changes do not look drastic, if indeed the system is characterized by an excess of heat. In addition, if the size of the heating batteries is chosen correctly, then there is a certain margin of efficiency, and this is the same 10-15%.

So it turns out that such a simple, even primitive at first glance, detail as a bypass is a universal tool for creating a pleasant living environment in the house, despite the fact that energy bills will delight homeowners with small amounts.

This seemingly insignificant detail optimizes the heat transfer of the heating unit, so a bypass in the heating system is not only desirable - it is necessary. The jumper (a piece of pipe) is mounted in the thermal route parallel to the heating radiators. Depending on the tasks assigned, this component is used either as a straight section closing the supply and return pipelines, or as a bypass line.

To understand why bypass is used and what it is in heating, you should consider the options for its use:

in the gravity network it is mounted parallel to the functioning circulation pump;
in mixing units of various types;
in closed and open systems based on one pipeline, the bypass is installed on heating radiators;
it is also used as a transition between the supply and return flows, in this case a small circulation circuit is formed that accompanies the heating of the heating unit.

When it comes to mixing units, installing a bypass in the heating system is necessary to connect the supply and return, and a three-way thermostatic valve is also used here. A piece of pipe is needed to direct liquid from both lines into the valve chamber so that water with the specified temperature parameters is formed at the outlet.

The jumper, accompanied by a three-way valve, allows the mixing principle to be used in the following network sections:

small circulation circuit in the case of a wood-burning boiler;
a collector that distributes coolant to the heating branches of the heated floor;
piping for heat accumulator.

In particular, a small circuit with the introduction of a bypass protects the solid fuel boiler from condensation during its heating.

The bypass unit, used in piping solid fuel units, is used as a safety element. Example: maximum heating is set, the furnace is full, and at this time the power supply stops. In such a situation, typical for domestic operating conditions, before the power supply is restored, the water in the radiators will already have cooled down. The boiler will still be hot at this time, because fuel processing continues in it. As soon as the pump turns on, the cold medium will enter the boiler jacket, as a result of which the cast iron section will burst - the resulting temperature shock will affect it. In these conditions, a pipe jumper is extremely necessary.

A similar mixing algorithm using a valve and jumper is used in heated floors when installing a distribution comb. After reaching the temperature standard in the heating circuits, the three-way valve shuts off the supply from the boiler, the media is driven by the pump along the internal heat line through the bypass.

Heating pump with bypass

The most common scenario for inserting a pump into a water heating system is directly into the pipeline (either into the supply branch or the return branch). In this case, a bypass is not installed, since when the unit is stopped, the small diameter of the pipes will not be able to maintain independent circulation of the liquid.

A bypass is required if a gravity system is initially used. Here, the main mode of heat supply will be forced distribution of the carrier using a circulation pump. During periods of no power supply, convection will contribute to the natural gravity of the environment. This solution involves installing pumping equipment on a bypass.

The unit can be assembled in two ways:

The direct line is equipped with a ball valve; shut-off valves, a strainer and a pump are mounted in the bypass branch.
The line rupture is complemented by a ready-made kit in the form of a bypass with a check valve and a pump.

In the first case, the gravity mode must be activated manually. During a power outage, residents will have to open one of the taps in the boiler room themselves. Otherwise, stopping circulation will cause the medium to cool down.

In the second scenario, a power outage will cause the check valve to automatically activate, which remains closed while the pumping device is operating. But there are two potential problems that can get in the way:

Some modifications of ball valves cannot be disassembled. If they fail or become dirty, you will have to dismantle and replace the entire assembly (except for the filter and pump);
U-shaped variations serve as an additional air collector; they require periodic turning of the manual release valve.

Therefore, professionals avoid schemes based on ready-made automatic bypasses; they prefer to assemble units that include a shut-off valve. In this case, the house will become noticeably cooler only half an hour after the power is turned off, during which time the main line can be opened. Another solution is to install a bypass unit using independent components and a check valve made of brass (in which the rubber ball is not fixed by a spring).

Installing a bypass on a radiator in single-pipe heating

High-rise buildings, inhabited since Soviet times, have single-pipe heating based on vertical risers, present in all apartments. Here, the distribution of the coolant is ensured due to high pressure and increased flow rate of the medium.

In this scenario, both connections are elements connecting the radiator to a single line, and the bypass fits between them. The jumper has a slight offset relative to the axis of the riser, due to which water enters the battery rather than flowing along an easy path. The solution works like this:

The flow of hot water on approach to the first heating element is divided into two parts - the first enters the radiator, the second flows into the bypass.
After the first flow has cooled by a couple of degrees, both parts are mixed, then half is sent to the main line. As a result, the resulting mixture has a temperature approximately one degree lower than it was initially.
This process occurs consistently in all heating devices. All consumers of the network receive a given amount of thermal energy (ideally in equal measure), because pumps drive large volumes of water through the mains, leveling temperature differences between the first and last links.

A similar solution is usually used in two-story residential construction. Despite the fact that the vertical riser serves only a pair of radiators, it is advisable to equip the top one with a bypass. The reason is the disproportion between the performance of household and industrial circulation pumps.

If we exclude the direct bypass jumper, the full volume of the carrier, having passed through the battery, will cool down more than in the described circuit. The temperature difference will lead to the fact that each subsequent apartment will receive less and less thermal energy, the last one will practically not warm up.

This is why the bypass is so important when installing a vertical single-pipe heat supply. Two-pipe distributions are based on independent lines for cooled and hot media; a jumper is not needed here.

The low power of the circulation pump installed in a country house is compensated by the large throughput capacity and diameter of the pipeline.

Errors often encountered during self-installation

Often, home craftsmen who decide to install new aluminum radiators themselves instead of old cast iron ones make two common mistakes:

they equip the direct bypass section with a ball valve in an attempt to direct all the heated water into the battery;
assemble a mixing structure, adding a three-way valve to independently regulate heat transfer.

The second example, at a stretch, can be called acceptable if we are talking about individual heating; here the homeowner can individually control the output of the heating unit. In standard apartment buildings, neighbors can be vulnerable if one person unbalances the system by taking away more heat.

Finally, if a bypass is added to the design of a heated towel rail, it is intended only for the convenience of replacing and servicing this heater. The element under consideration does not affect heat transfer, since the pressure and speed of movement of the medium in the water supply here change to an insignificant extent.

Many people have heard that to increase the efficiency of the heating system it is necessary to install a bypass, but they don’t even know what it is. This beautiful English word hides a parallel pipeline to the main heating system in a certain area. A bypass is used when it is necessary to constantly regulate the temperature in a separate section of the network and to be able to change the heating battery without turning off the entire heating system. To make adjustments possible, appropriate pipeline fittings are installed on the bypass.

Why do you need a bypass?

What exactly does installing a bypass allow you to do in reality? For example, if there is a bypass for an individual water meter, this will allow it to be replaced without turning off the water supply to the house or apartment. The same can be said about circulation pumps integrated into the heating system. The presence of a bypass allows you to switch to natural circulation in the event of a power outage when the pump stops working. If there is a bypass with an adjustable thermostat next to the radiator, then this allows you not only to set the required temperature conditions, but also to replace the heating device if it fails, without turning off the heating system fully.

Basically, a bypass is an element of a single-pipe heating system. Such a system has a number of advantages, the main one being inexpensive installation, and a large number of significant shortcomings. Installing a bypass allows you to minimize the disadvantages of a single-pipe heating system. By design, a bypass is pipe jumper, connecting the “return” with the supply pipeline. A jumper is installed in the immediate vicinity of the radiator and two ball valves are mounted on it. This allows hot water to pass from the supply pipe to the return pipe, bypassing the heating device, thereby adjusting the temperature in the room.

Bypass installation

Jumper installation

Jumper installation requires compliance with certain rules:

In terms of its diameter, the bypass pipe should be smaller in diameter than the supply and return pipes. This is due to the law of hydraulics, when water bypasses the radiator along the path of least resistance;
installation should be carried out as far as possible from the riser and in close proximity from a heating device;
if automatic adjustment is planned, then instead of ball valves it is necessary to install thermostats.

For clarity, we can give an example of installing a bypass in a single-pipe heating system of a country house, the advantages and disadvantages of such an installation, the rules for carrying out installation work, and what pipeline fittings will be required.

Installing a circulation pump

In country houses where the heating system operates autonomously, it is mandatory installation of a circulation pump is required. This allows not only to distribute the coolant evenly throughout the entire heating system, but also to save significantly, since heating the entire house will take much less time than with natural circulation.

The problem is that the circulation pump requires availability of electricity, and given that in remote suburban areas there can be constant shutdowns, certain problems arise with the circulation of the coolant. They can be solved by simply installing a bypass. The main thing for the system to work productively both with and without a working circulation pump is to install a bypass in compliance with all technological requirements.

Effective operation of the circulation pump is only possible if it directly integrated into the heating system. In this case, it is advisable to install it in the return line and this requirement is explained quite simply: to allow the circulation pump to work out its warranty period. The pumping device consists of:

various rings
seals
rubber cuffs

If the pump is installed on a supply pipe, then under the influence of high temperatures, it is very will fail quickly, and on the “return” the temperature of the coolant is an order of magnitude lower, which allows it to work for a longer period.

It is well known that the fewer curved sections in the heating system, the more works more efficiently. Therefore, they try to install the circulation pump in a straight section. But this is if there is no bypass. If it is, then in this case the coolant will have to overcome three obstacles at once: shut-off valves and two outlets. This will greatly reduce coolant circulation, therefore, in a single-pipe heating system with a bypass, the pump should be installed directly on the jumper pipe. What shut-off valves and consumables may you need in this case?

Please note that, if possible, the coolant should flow along straight sections. The more different fittings there are in a heating system, the less efficiently it works. This is the law.

Now let's turn to a situation where the pump is installed on a straight section, and the coolant must flow naturally through bypass. In this case, he will have to overcome two outlets and a valve (valve), which cuts off the bypass from the main. For hot water, 3 obstacles at once in a small area is too much. There will be circulation slow, which means that the efficiency of the system will drop sharply.

So, it’s decided - the circulation pump is always must be installed in the bypass section. What consumables and shut-off valves are needed for this? First of all, the valves. They come in two types:

with ball-shaped locking device
with movable rod

The movable stem valve has one significant drawback. Its valve seat diameter is almost two times smaller than the diameter of the heating pipe. This serves as a barrier to the coolant and due to this, there is a sharp decrease in the efficiency of its circulation through the heating pipeline. Therefore, their installation in the bypass system is not practiced.

Ball valves exactly match the diameter of the heating pipe, but if they are not used for a long time, they can become stuck and it will be very difficult to open them, if such a possibility exists at all. There are two ways out of this situation. In the first case, install double diameter bellows valve. In the second case, do not forget to regularly open and close the ball valves. This is if we talk about the bypass system. It is much more difficult with the central main line, parallel to which the bypass is located. Here you will need to install several types of valves, with the help of which you will adjustable pressure and quality of hot water.

Installing a locking device

First of all, you will need to install a shut-off device - a check valve or tap. If the central line of your heating system is not blocked, then the coolant supplied to the system by the circulation pump under pressure will move in a closed small circle. The traffic pattern in this case will look like this: bypass-main line-bypass. To prevent this from happening, when the circulation pump is running, the main line must be closed. If you install a ball valve, it will need to be closed manually. When installing a check valve, the line will be closed automatically.

It would be a good idea to install it in the bypass directly before the circulation pump. replaceable mechanical filter, which well retains foreign impurities found in the coolant. This will increase the life of the pump, especially if hard water is used as the coolant. It is recommended to install the filter on a horizontal section of the pipeline.

As can be seen from the above, in an autonomous heating system, the bypass is one of the most important elements of the network. Therefore, when installing heating, special attention should be paid to installing a bypass and try not to violate the technological scheme.