Fittings for plastic pipes: types, applications, an overview of the best manufacturers

Amir Gumarov
Checked by a specialist: Amir Gumarov
Author: Tatyana Zakharova
Last update: March 2019

Plastic pipes for performance are ideal for creating water supply and heating systems. According to the rules of installation, to connect individual fragments, it is necessary to use fittings for plastic pipes, other options are not suitable.

The article we presented describes in detail the types of fittings and how to install them. Valuable recommendations are given to ensure that a competent choice of connectors is made. Based on our advice, you can independently cope with the assembly and installation of the system.

Pros and Cons of Plastic Products

Metalloplastics has characteristics that allow you to create reliable systems having a service life of 15 to 50 years. The outer diameter of the products is 16-63 mm. Fittings must fully correspond to the diameter of the pipes, while the wall thickness (2-3 mm) must also be taken into account.

For internal wiring, the best diameter is 32 mm. Water is most often supplied to heating appliances through narrower products - from 22 mm to 24 mm.

Fittings for plastic pipes
The merging of two pipes made of metal-plastic occurs by means of fittings, which also have different diameters, differ in the method of installation, purpose and configuration. Production material - stainless steel and brass

Pipelines made of metal-plastic withstand temperatures up to + 95ºС (with interval increase up to + 110ºС), therefore they are used for assembling heating systems. There is a threshold at which pipe freezing occurs - it is -40ºС. Working pressure - 1 kPa. When the temperature decreases, the pressure can increase without the risk of system failure to 2.5 kPa.

Advantages of metal-plastic pipelines (when compared with analogues of metal, PVC and polypropylene):

  • Quick installation. Welding or soldering is not required to connect the individual segments; enough keys or a special crimping tool are enough.
  • No need to be coated with a protective paint with an anti-corrosion compound.
  • Systems with one-piece connections are designed for installation in screed or in walls.
  • The weight of pipes and fittings is small, which also facilitates installation in various ways.
  • During installation, a minimum of waste is obtained.
  • Protected against stray currents.
  • Pipelines with detachable connections are easy to repair, to replace fittings.
  • They have the ability to connect additional devices without disassembling the entire system.
  • With the help of special fittings combined with metal pipes.

There are also disadvantages, and they must be taken into account when installing the wiring independently. The cost of MP pipes is quite high, respectively, and fittings are more expensive. Compare specifications plastic and polypropylene pipes You can, having familiarized with article recommended by us.

If the temperature of the fluid in the heating pipe is constantly maintained in the region of the maximum (+ 95ºС), the service life of the pipe is reduced by half. The polymer layer is destroyed under sunlight, therefore, the pipes should not be in the ultraviolet exposure zone.

Types of fittings for metal

For water pipes or heating wiring various fittings are required. The good thing is that now in the store you can buy connecting elements of any configuration and you do not need to invent anything yourself. Usually, accessories are bought together with pipes so that the diameter matches. Consider which fittings may come in handy.

Designation of valves

The shape of the part (straight, angular, cruciform) depends on the purpose of the part. We will consider the main types on the example of VALTEC products, which are often preferred to other brands because of the good price / quality ratio:

In addition to the listed elements, plugs, fittings, adapters for pipes of a different diameter, water sockets are used.

To find out exactly which fittings are required for the assembly of communications, it is necessary to draw up a general diagram and calculate the number of joints, angles, intersections, etc.

Brass fittings
Strength is attached to the parts by the high-strength brass of which the body consists, and stainless steel for press sleeves. The maximum working temperature for which they are designed - + 115ºС

Classification by connection method

Often you can find a classification in which accessories for metal-plastic pipes are divided into three groups: threaded, compression, press fittings. This is a wrong division, since the threaded appearance assumes the presence of a factory or independently made internal or external thread on the pipe and on the fitting.

Plastic pipes, unlike metal pipes, are not cut at the ends before crimping, so it is correct to consider two categories of fittings:

  • compression (collet, crimp);
  • press fittings.

A variety of parts is selected depending on the installation scheme and the need for a monolithic or prefabricated wiring.

Option # 1 - Compression Fittings

Crimp connection is used quite often, especially in open sections of the pipeline. The crimping process is as follows.

When tightening the union nut (worn on the pipe from the outside), a split ring (collet) presses on the outer surface of the pipe, as a result of which the inner surface of the pipe is tightly pressed against the fitting. As a result, a semi-detachable connection is formed, strong, but requiring a tightening from time to time.

Crimp fitting diagram
Crimp fitting diagram. Before the fitting is placed in the pipe, first the union nut, then the split ring is put on it alternately. In the process of crimping, all elements are tightly adjacent to one another, forming a sealed bundle

It is worth knowing that there are two types of crimp fittings:

  • With integrated fitting. The fitting and housing are indivisible. When crimping, the fitting is inserted into the pipe, the body remains outside. The case is usually made of brass, sometimes nickel-plated.
  • With threaded adapter. It features a plug-in type fitting. It has a specific purpose - they act as terminal connectors during the installation of radiators, manifolds, fittings for pipes.

The dimensions of the adapters depend on the diameter and thickness of the pipe machines. Adapters also differ in the size and shape of the crimping nut, the shape of the seal (flat or conical).

Adapter Euroconus
An adapter sample, the fitting of which has a slightly elongated, tapered seal on one side (Euroconus). Production material - nickel-plated brass. Technical characteristics: diameter - 20 mm, maximum working temperature - + 95ºС, pressure - 10 bar

Crimping does not need a special tool. Usually use open-end wrenches or adjustable wrenches.

Option # 2 - Press Fittings

The connecting elements of the second type differ from compression analogues in design and crimping result.

Radial Press Fitting Design
The design of the radial press fitting is based on three components: a brass body, a steel press sleeve and a plastic ring for fixing. Correctly installed connecting element is not inferior in strength to pipe material

Brass is recognized as the ideal body material, but some manufacturers also use bronze. Both materials work well without additional coating, but tinned and nickel-plated parts are also very popular. Along with brass, PPSU and PVDF are also used - cheaper, more durable and not subject to corrosion.

The best material for a press sleeve is AISI 304 stainless steel. It is stronger and more stable than aluminum, which is used much less often. Some sleeves have revision inspection holes necessary to control crimping.

O-rings (gaskets) are made of EPDM or NBR. Options with two seals are more common than with one.

Plastic thrust rings are located between the sleeve and the housing. They protect metal parts from electrical damage. Some manufacturers paint the plastic in different colors to make it easier to determine the diameter. Sometimes the rings are equipped with a small protrusion for precise installation of the crimping tool.

According to the rules installation of press fittings performed using a special tool - press pliers. Fans usually use manual modification, it is more convenient for professionals to work with hydraulic and electromechanical devices that simplify the crimping process.

Crimping pliers
Press tongs are a universal tool, as they have a set of interchangeable nozzles. The choice of a certain standard size of equipment is made based on the diameter of the MP pipe and the shape of the profile. Popular sizes - 16, 20, 26, 32 mm

O-rings on fittings from different manufacturers are located in different places. During crimping, the tool presses the sleeve as tightly as possible, and the location of the rings plays a crucial role.

For this reason, it is strongly recommended that you use press fittings and a crimping tool from the same manufacturer, otherwise the connection technology will be compromised.An exception is the products of companies that prudently produce universal systems.

Crimp fitting installation technology

When the right tool is at hand, the crimping process of the compression fitting is quick and easy. After two dozen procedures, the hand is full, and each movement is brought to automatism. Perhaps for this reason, pipelines assembled by professional plumbers serve about 7 years, even without additional twisting (although it is recommended).

So, to install a compression fitting on a metal-plastic pipe, you will need scissors (pipe cutter), a calibrator, spanners in size. Manually straighten the piece of pipe to be crimped, and proceed according to the following instructions:

As a result of crimping, the union nut should not “walk” through the pipe, even if you try to move it by hand.

A few professional tips will help you avoid the flaws when installing a compression fitting:

  • Before installing the fitting in the pipe, be sure to check the presence of o-rings: they must be in the grooves intended for them. To prevent the rings from getting loose during installation, some craftsmen lubricate the fitting with soapy water.
  • If the fitting does not enter the pipe, and the o-rings are pulled off during installation, be sure to perform flaring with the calibrator. There is no special tool at hand - use the end of the wrench.
  • When tightening the union nut, check the force: excessive efforts can damage the edges and deform parts of the fitting.
  • During installation, two keys are used: one holds the fitting, the other tightens the nut. It is better to choose the sizes in advance, since they are most often non-standard. If there is no suitable size, an adjustable wrench will help.

A properly installed compression fitting will withstand the pressure in the system even when the compressor or pump is running. Approximately once a year it is necessary to inspect, and if digging is detected, it is recommended to tighten the nuts.

Press fitting technology

Press fittings differ in design and, accordingly, in the method of installation. Before installing the connector, carefully inspect the connectors for plastic pipes (sleeve, gaskets) and prepare press tongssuitable in profile and size (ideally, the same manufacturer).

We prepare the pipe in the same way as for the crimp fitting - we straighten, mark, carefully cut it pipe cutterdesigned for working with metal plastic. It is important to process the end part: remove the burrs, make the rim smooth and even. We mount the fitting in the following order:

When working with a hand tool, it is necessary to remember one subtlety of crimping: it must be performed twice. That is, after the first clamping, it is necessary to loosen the fixation, rotate the pliers along the axis by about 30º and repeat the procedure.

With Tips and Valuable Implementation Tips crimping pipes made of metal You will familiarize yourself by reading our recommended article.

What you need to know about the difference in methods?

Before choosing the type of fittings installed on the water supply or heating system, you need to get acquainted with the differences between two different crimping methods:

  • The pipeline with compression fittings is serviced (it needs to be tightened about once a year), and the system with press fittings is monolithic, not serviced.
  • For the installation of compression parts, improvised tools are sufficient; for the installation of a press sleeve, special press pliers are required.
  • A system with compression fittings can be disassembled at any time to replace parts or repair, a pipeline with press fittings, if necessary, must be completely replaced.
  • The collapsible system should be in sight (for regular maintenance), monolithic joints can be poured with screed and mask in the walls.

If the cost of a set of connecting elements is important, then keep in mind that press fittings are about 1.5 times cheaper than crimp counterparts.

Overview of the best manufacturers

Companies engaged in the production of fittings usually produce both types, so consider four of the most popular brands:

In addition to these brands, in the market of fittings for metal-plastic pipelines you can find high-quality products COMAP (France), ALTSTREAM (Russia), Henco (Belgium), UPONOR (Finland).

Conclusions and useful video on the topic

You will learn how to distinguish a crimp fitting from an element with a press sleeve and what to consider in the crimping process from the following videos.

Video # 1: The process of installing a press fitting on a pipeline:

Video # 2: Details and availability of the device and installation of press fittings:

Video # 3: Practical tips for working with crimp fittings:

One of the advantages of metal-plastic pipelines is the ease of assembly using special parts.Crimp and press fittings differ in the installation method and the need for maintenance, but both types allow you to create functional, reliable, water supply and heating systems that have been operating for decades.

Subject to the installation rules, you can independently, without the help of professional plumbers, cope with the installation of intra-house communications.

Please write comments in the block below. Share information with visitors to the site that will help to correctly assemble and connect sections of the pipeline made of metal-plastic. Ask questions, post a photo on the topic of the article.

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Visitors Comments
  1. I loved working with metal, but sometimes such surprises come out that I take my head. Few people risk even wringing crimp fittings into the wall or in the screed, because over time they have the ability to loosen for various reasons - expansion of the material, water hammer, etc.
    Even expensive and branded are not immune from this. I had such an incident in the bathroom on hot water. The pipe stood for 8 years, and a small leak began on the fitting.
    I had to do destruction, hollow out the tile, and in the shtrobe, in a limited space, put on and press on the fitting with ticks again - this is not an easy task.
    Tormented, I still remember this hassle.