How the boiler is strapped with polypropylene: the rules for the construction of the pp circuit

Alexey Dedyulin
Checked by a specialist: Alexey Dedyulin
Author: Maxim Fomin
Last update: July 2019

Engineering systems from affordable polypropylene pipes can last up to half a century. Polymer tubular products are extremely easy to install, only one soldering iron is needed to connect them. But is this material suitable for heating systems? Will the boiler piping polypropylene durable and reliable?

If everything is done according to technology, then plastic pipelines quite safely deliver the coolant to the batteries.

What is the boiler piping and what does it consist of?

The harness is a combination of heating equipment that ensures the transportation of heated water to radiators and the failure-free operation of the heater itself.

On the one hand, it helps to evenly distribute heat throughout the house, and on the other, it increases the reliability of the entire heating system, protecting the boiler from overheating and excessive fuel consumption.

There are certain nuances in the boiler equipment strapping device:

Also, by strapping the heating apparatus is meant the calculation of the parameters of all elements of the internal heating system and their installation. Heating system It should work not only reliably, but also correctly. A large number of additional devices and complex wiring can seriously reduce its effectiveness. Everything must be done correctly.

Proper strapping increases boiler efficiency
Correct piping increases the efficiency of the water heater and its reliability

There are simply no options for heating systems that are optimal and ready for all buildings without exception. To achieve the maximum return on a particular boiler, it is necessary for each house to prepare an individual heating system project individually. But there is a certain set of standard rules and a list of typical equipment.

Gravity heating boiler piping
In the simplest scheme of the heating boiler strapping during gravitational movement of the coolant, a minimum of shut-off and adjustment devices (+)

Depending on the type of fuel used, the quadrature of the house, the model of the heater and its location, polypropylene strapping is done according to various schemes.

But in all of them there are:

  1. Boiler (single-circuit or dual-circuit).
  2. Expansion tank. Hydraulic with a diaphragm or a conventional tank depending on the type of heating system.
  3. Polypropylene pipes and fittings.
  4. Batteries (cast iron, steel, aluminum, bimetal).
  5. Bypass (sections of the pipeline that allow you to disconnect individual devices from the circuit). Recommended for all types of networks, but not always used in simple flow diagrams.

According to the principle of coolant movement, the heating circuits are divided into systems with natural (gravitational) and artificial (pumping or forced) circulation.

Options for tying the boiler with polypropylene
The circulation pump is a mandatory component of forced-type heating. It is needed to stimulate the movement of the coolant (+)

In a forced-type heating network, the above set is complemented by:

  • Mayevsky crane.
  • Circulation pump.

In the scheme with the supply of coolant to each device, the collector - distribution device is necessarily included on the supply and return pipes intended for it.

In heating circuits that require mandatory adjustment of the qualitative and quantitative characteristics of the circulating liquid or steam, control devices are built in:

  • Pressure gauge.
  • Thermostat.
  • Hydraulic needle if pressure equalization is necessary.

In a system with forced circulation of the coolant to maintain a given pressure in it, expansion tank with a membrane. And in its gravitational analogue, an ordinary open tank without any inserts inside will be enough.

Boiler piping diagram with air pipe
The expansion tank of systems with the natural movement of water is in contact with the external environment, due to which they can be saturated with air. To prevent this phenomenon, systems are supplemented with an air circuit that collects and removes air

The expansion tank of the simplest heating system with the natural principle of movement is an ordinary tank with a pair of pipes screwed in or welded into it. One of them is a supply pipe, the second is a signal pipe, which tells about filling the tank with water that expanded when heated.In a more complex version of the tank, four pipes are already screwed.

With an increase in the coolant volume above the norm, the excess is simply discharged through the signal pipe. In the future, the coolant will expand in the same way and take the previous volume, but there will be no overflows into the signal pipe. By analogy, air is taken off spontaneously; therefore, there is no need to install Mayevsky cranes.

The boiler piping consists of many elements
Between the boiler and polypropylene pipes a control and safety group is built from various sensors, regulators and emergency valves

Circulation pumps in circuits based on the natural principle of movement of the coolant are not used. In such a system, water moves under the influence of gravity.

She does not need additional pressure boosters. On the one hand, this increases the reliability of heating (there is simply nothing to break down), and on the other, it reduces the quality of heating of the far rooms in the house (the coolant reaches the extreme ones already cooled down).

The intricacies of installing a heating system from polypropylene pipes are described in detail in one of popular articlesposted on our website.

Polypropylene pipes in heating systems

Polypropylene fittings and pipes (PPR) are popular due to their low cost and ease of installation. They are not subject to corrosion, have smooth internal walls and serve no less than 50 years declared by the manufacturer.

There are several types of these tubular products, which differ in technical characteristics and purpose.

In the construction of heating systems, as well as in the design of hot water circuits close to them in operational parameters, the following are used:

  • Pipes marked PN 25. Products with reinforcement made of aluminum foil. They are used in systems with a nominal pressure of up to 2.5 MPa. Operating temperature limit + 95º С.
  • Pipes marked PN 20. A reinforced version used in hot water branches of double-circuit heating boilers. The period declared by the manufacturer will be fulfilled if the temperature of the coolant is not higher than + 80º C, and the pressure is up to 2 MPa.
  • Pipes marked PN 10. Thin-walled polymer products. Used if the boiler supplies the heating medium to the underfloor heating system. Operating temperature not higher than + 45º С, nominal pressure up to 1 MPa.

Polymer pipes are suitable for all known laying methods: open and hidden. But this material has a large coefficient of thermal expansion. When heated, such products begin to slightly increase in length. This effect is called thermal linear expansion; it must be taken into account when constructing pipelines.

PPR pipe marking
The boiler should be tied with polypropylene pipes, which in the marking have an operating class of 5, an operating pressure of 4–6 atmospheres and a nominal pressure of PN 25 and higher

To prevent the destruction of polypropylene heating pipelines, compensation loops can be installed. But it is easier to take multilayer pipes, the reinforcement in which is specifically designed to compensate for this extension. A layer of foil inside polypropylene pipes PN 25 reduces their thermal elongation by half, and fiberglass by five times.

Features of installation of PPR pipelines

When tying the boiler polypropylene pipes and fittings they are connected mainly by cold or hot welding, in the case of connecting to metal pipelines, threaded connections are used. Screwing is much more convenient, but because of them the assembly of the system will cost much more.

True, if you want to connect a polypropylene pipeline to a metal colleague, you can not do without threaded fittings.

Fittings for tying the boiler with polypropylene
An extensive line of fittings is available for forming linear and nodal joints of polypropylene pipes.

“Hot” is welded with a special apparatus (soldering iron, “iron”). The pipes are heated with a suitable nozzle to a melting point of 260 degrees, and then the parts with softened edges are pressed against each other. The result is a reliable and monolithic connection.

Before welding, the foil of reinforced pipes must be cleaned without fail. Otherwise, it will interfere with the connection of polymer products, making the seam fragile. With fiberglass, these extra actions will not be required. It melts quietly with plastic.

Polypropylene Soldering Technology
PPR soldering technology is extremely simple, all work can be done with your own hands (+)

Cold welding involves the use of specialized adhesives. In recent years, this method is rarely used, because the result is not reliable enough.

In heating systems, threaded joints should be sealed with paronite or high-temperature sealant. Do not forget about the sufficiently high operating temperature of the coolant.

There is one more nuance of using polypropylene for tying a heating boiler. Antifreeze with plastic is a rather bad combination. It is recommended to use water as the coolant for the system of plastic pipes.

Choosing a heating system wiring diagram

There are several options for tying the boiler with polypropylene. For each house, this scheme is selected individually. What is optimal in one building may be ineffective in another.

In addition, heating systems according to the principle of movement of water are divided into: forced with a hydraulic pump and gravity (gravity, natural), there is still a classification for the arrangement of pipelines. According to their structure, they are one- and two-tube, collector beam or analogs with closed rings.

Which is better: gravity or pump?

AT gravity circuit heated water to the radiators from the boiler flows by gravity. A hot coolant having a high temperature always tends to replace a colder liquid by itself. This heating boiler piping system is the easiest to assemble. In addition to the heater, there are pipes made of polypropylene, radiators and an expansion tank.

In the variant with the top wiring, the water rises to the highest point after heating - to the expander, and from there it goes down to the batteries. After heat transfer, it returns to the boiler, where it is again heated, then starting a new cycle.

According to this scheme, heating is arranged in many houses in domestic villages. Only there is a solid fuel stove. This is the easiest and cheapest way to organize the heating of a small cottage. However, it has limitations both in the number of connected radiators and in the remoteness of the last of them from the water heater.

Polypropylene boiler piping diagram
The layout of the harness with the natural movement of water is the simplest of all possible options, it has a minimum of nodes and connection points for pipes made of polypropylene

More complex and expensive forced system. However, it greatly simplifies the creation of comfortable temperatures in individual rooms. In it, the coolant moves already due to the stimulation of its movement by the pump.

The choice of the layout of polypropylene pipes and the boiler itself are closely related. The natural circulation system is non-volatile. If the water heater in it does not require power from the mains, then even in case of power outages, the house will be heated.

In a forced circuit, the pump needs a constant power supply to operate. Therefore, the boiler for it is best to choose an electricity dependent one, which has additional features. But to insure against voltage problems, you will have to buy a backup generator or uninterruptible power supply to them.

Which heating scheme is better to choose?

There are many ways to separate pipelines from polypropylene from the boiler to heating radiators.

But all these schemes are divided into:

  • single tube;
  • two-pipe.

AT single pipe systems Heated water supplied as a coolant is supplied and discharged by one pipe. In two-pipe for supplying coolant and return, i.e. drainage of cooled water back to the boiler for heating, separate lines are being constructed.

According to the method of connecting the working components, the heating circuits are divided into:

  • tee;
  • collector.

Tee types can be used both with gravity and forced circulation. The collector circuit can only work if there is a circulation pump.

Comparison of single and double pipe systems
The one-pipe scheme is obviously cheaper than the two-pipe, but the radiator farthest in the chain from the boiler in it receives a minimum of thermal energy (+)

The one-pipe method involves the laying of one looped line and the series connection of batteries to it. In a two-pipe scheme, two independent pipelines with hot water and return are coming from the boiler. And already radiators are connected to them.

At collector harness one or two collectors are built into the system, from which separate pipes are thrown to each battery. Also, such a distributor allows you to connect to the boiler "warm floor", made all of the same PPR.

Collector circuit
Collector wiring makes it possible to create effective heating systems for houses of large area and different storeys (+)

The use of collectors and separate risers for each battery leads to a significant increase in the cost of both design and installation. At the stage of project preparation, more complex calculations have to be done. And during assembly, a much larger volume of polypropylene is consumed. But then a system is obtained, each part of which can be adjusted to specific conditions and requirements.

Polypropylene circuit for different boilers

Most manufacturers of water heaters recommend the first meter of the pipeline from it to be made of metal. This is especially true for solid fuel devices with a higher outlet water temperature. When strapping, polypropylene should already be connected to this branch, otherwise, in the event of a malfunction in the boiler, it will receive a heat stroke and may burst.

Option # 1: Gas Water Heater

Polypropylene tying of a gas boiler is recommended to be carried out using a hydraulic arm and a collector. Often, gas models are already equipped with built-in pumps for pumping water. Almost all of them were originally designed for forced systems.

The most reliable in terms of safety will be a circuit with circulating equipment for each circuit behind the collector.

In this case integrated pump will pressurize a small section of the pipeline from the boiler to the distributor, and then additional pumps will be involved. It will be on them that the main burden for pumping the coolant will fall.

Gas boiler piping
A gas boiler can be tied with polypropylene without long metal pipes; water in such a heater rarely heats up to 75–80 degrees

If the gas boiler has a cast-iron heat exchanger, then when it is strapped into the system, an additional heat accumulator should be installed.It will smooth out sudden changes in water temperature, which have a negative effect on cast iron. With spasmodic heating or cooling of the coolant, it can even burst.

When tying a dual-circuit apparatus with parallel heating of water for domestic hot water, additionally fine and rough filters will have to be installed on this branch. They should also be mounted at the entrance to the water heater, where cold water is supplied.

Option # 2: Solid Fuel Model

The main feature of the solid fuel boiler is its inertia when the fuel supply is cut off. Until everything in the furnace burns out completely, he will continue to heat the coolant. And this can adversely affect polypropylene.

When tying a solid fuel boiler, only metal pipes should be connected to it immediately, and only after a meter and a half can polypropylene be embedded. In addition to this, it is necessary to provide a backup supply of cold water for emergency cooling of the heat exchanger, as well as its discharge into the sewer.

Solid fuel boiler
A section of the pipeline from the solid fuel boiler to the collector should be made of metal, and then you can strand with polypropylene - only this will protect the plastic pipes from overheating

If the system is built on forced circulation, then it will definitely need to install an uninterruptible power supply for the pump. Water must constantly remove heat from the furnace, where solid fuel burns, even in the event of a power outage.

In addition to it, you can make a small gravity circuit or equip all batteries bypasses to disable individual sections system. In case of accidents, this will allow repairing the damaged section when the heating is running.

The solid fuel boiler must be covered with a protective casing, which limits the spread of heat from the walls of the furnace to the boiler room. But even with it, the collector and plastic pipes should be removed away from the stove.

Option # 3: Oil Fuel and Electric Heaters

A developmental or diesel boiler is tied with polypropylene in an identical pattern with a solid fuel analogue. The polymer must be removed from it as far as possible.

Electric boiler
When tying an electric PPR boiler, you don’t have to worry about pipe breaks, it has protective automation that prevents water from reaching a boil

Heat coolant in the water heater on electricity to temperatures critical for polypropylene is virtually eliminated. In the event of a power failure, it simply stops working. In this case, the pipes are protected against water hammer by a hydraulic accumulator and valves to relieve excess pressure.

Conclusions and useful video on the topic

Video # 1. How to choose pipes from PPR:

Video # 2. Solid fuel boiler piping technology:

Video # 3. How to tie a heater in a two-story cottage:

When choosing a boiler piping scheme made of polypropylene pipes, it is necessary to take into account all the features of a particular building. The process of installing pipelines and connecting equipment is simple, even a novice master can cope with it.

Using a soldering iron for polypropylene fittings and pipes is easier than ever. But it’s better to entrust the specialist with the preparation of the heating system design, errors are not allowed here.

If you want to share personal experience gained during your own assembly of polypropylene strapping, have you found any shortcomings or would you like answers to your questions? Please write comments in the block below the test article.

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Visitors Comments
  1. Dmitry

    When I was making my own heating, I bought a reinforced PP pipe, a Czech headquarters ecoplastic for some reason. The diameters were 20 and 25. So, special cleaning devices for each diameter cost me dearly, as did this pipe with aluminum. Although I know, there are craftsmen who cut this thing with a knife.
    Now I understand that it was possible to save, namely, to use compensators and a cheaper pipe PN-20. Because I operate a double-circuit wall boiler at 65ºС. Reinsured, so to speak.

  2. Ildar

    You guys, of course, well done, but in the photo of the boiler piping vailant, the circulation pump must be installed correctly. And so everything seems to be the norm.

  3. Ildar

    1. In the video No. 3, the oblique filter next to the electric boiler is not standing correctly (when cleaning the filter, all the debris will spill out into the pipeline).

    2. A safety group is placed after the boiler, but before the taps, it may happen by accident or if the tap is intentionally closed, the emergency valve will not work during overheating and there will be “HAPPINESS” for you when replacing the heat exchanger and the polypropylene feed pipe. In this case, the warranty flies automatically.