Installation and connection of metal-plastic pipes

Recommendation points

• Connection selection
• Compression fittings
• Press fittings
• Push fittings
• Installation of metal-plastic pipes
• Operation and maintenance of metal-plastic pipe systems

There are several systems for joining metal-plastic pipes – compression, press fitting, push fitting, collet connection. We will tell you how to choose the right pipe and which connection to use for installation, we will talk about the advantages and disadvantages of various connecting elements.

Connection selection

The reliability of a system consisting of metal-plastic pipes depends on the reliability of each of its elements, as well as their connections. All compounds can be conventionally divided into two large groups:

• one-piece;
• detachable.

Permanent connections do not require maintenance, but in the event of pipeline repairs, it is necessary to break the integrity of the structure.

Detachable connections can be easily disassembled for repair, maintenance or redesign of the pipeline.

When installing metal-plastic pipes, both types of connections are used.

Compression fittings

Some of the easiest to install are compression fittings. To connect parts of the pipeline in this case, only a wrench is needed from the tools.

The connection consists of: a fitting, a union, a ferrule and a union nut. Some manufacturers have combined the union and the fitting into one piece.

The assembly sequence is as follows:

1. A union nut is put on the pipe, then a crimp ring.
2. It is imperative to check the presence of sealing elements on the fitting, insert the fitting as far as it will go.
3. Tighten the union nut. It is advisable to use a second wrench to facilitate work and fix the fitting..

The compression connection is a detachable one, but remember that when disassembling it, it is necessary to replace all the sealing elements with new ones, otherwise you risk getting an unreliable connection. Such a connection must be serviced periodically by tightening the union nut..

Press fittings

Press fittings are one-piece connections. They are more reliable than compression fittings, which allows hidden laying of pipelines and joints in walls and underfloor heating screed. This significantly expands the possibilities of engineering communications design..

Fittings are made of brass, bronze, PPSU (polyphenylsulfone), PVDF (polyvinylidene fluoride). Metal fittings can also have an external coating – nickel plating or tin plating (tin plating). Polymer fittings are in no way inferior to metal fittings in terms of technical characteristics, but much cheaper.

Press sleeves for fittings are made of AISI 304 stainless steel, some manufacturers use aluminum.

The necessary part of the pipe is cut off with a pipe cutter, after which it is calibrated. At the same time, the gauge removes the inner chamfer and removes the ovality that will inevitably occur when cutting. The fitting is inserted into the pipe until it stops. The ferrule has holes for visual inspection of the fit of the pipe, it should be visible. Next, you need to crimp the connection. To obtain a reliable connection, you need to use special pressing tongs. There are several profiles of the crimping pliers working surface. The pliers should push the sleeve in a specific place, depending on the number and placement of the o-rings. The most widespread are the TH and U profiles, H, B, F are often found, there are others.

Push fittings

Push fittings, also called push-fit press fittings, were developed a few years ago and are not yet widely used. Made of brass.

The installation of this connection requires a modified jaw and expander to align and expand the pipe..

Cut the pipe to the required length. A brass coupling is put on the pipe. The end of the pipe is inserted into the expander and processed, then the fitting is inserted into the pipe. Press jaws grip the fitting and the coupling, pressing it onto the fitting.

This type of connection is maintenance-free one-piece, and is also excellent for concealed installation. The main advantage of this connection is the elimination of installation errors. The liner is pressed on with a manual or hydraulic press.

Installation of metal-plastic pipes

The big advantage of metal-plastic pipes is the easy and simple ability to create shaped elements from it, turn the pipe to any required angle, even roll it into a ring.

When installing pipes, it is advisable to use a manifold. This will ensure a uniform water pressure for all consumers. From the collector to the consumer, if possible, use the pipe “one thread”, this will reduce the number of connections and increase the reliability of the system.

To bend metal-plastic pipes, electric pipe benders and hand-held conductors are used – springs. The spring can be inserted into the pipe or worn on top. When making small fittings, it is better to use an internal conductor. In this case, you have complete control of the pipe in your hands without slipping the conductor. If you need to make several turns or turns of the pipe (for example, when laying a warm floor), you cannot do without an external conductor.

If you do not have the skills to work with a metal-plastic pipe, it is not recommended to bend the pipe by hand without a tool. In this case, you can narrow the cross-section of the pipe or simply break it at the bend..

Pipes that are laid in walls and floors are equipped with maintenance-free one-piece connections. Pipelines that run openly are equipped with any convenient connection. It is advisable to use compression joints when connecting taps and other plumbing fixtures. This will allow for quick replacement or repair of the device..

Fastening of pipelines to the wall is carried out using fixed and movable supports. The material for the manufacture of supports is polyvinyl chloride or another type of plastic. Using metal supports, elastic spacers must be installed on them. Supports must not deform the pipe or its outer layer. For open pipe laying, split supports are used.

Thermal insulation of pipes must be carried out in the following cases:

• when laying on the ground;
• when laying in an unheated subfield;
• at openings where pipes may freeze;
• hot water risers;
• to protect cold water pipes from condensation.

Foamed polyethylene is used as thermal insulation.

After completing the installation of the system, it must be rinsed with water until the water comes out without mechanical impurities.

Operation and maintenance of metal-plastic pipe systems

When installing a system of metal-plastic pipes, it is necessary to take into account the negative effect of ultraviolet radiation on the pipe material. In this case, it is better to provide open wiring with a screen – the same thermal insulation. Premature aging of the pipe also causes high-frequency electric fields.

During the operation of a pipeline made of a metal-plastic pipe, it is necessary to periodically, at least once every six months, check the compression fittings. Over time, as well as due to hydraulic shocks, temperature changes in the heating system, the nut on the fitting can “release” and it must be tightened.