The water supply system from metal-plastic pipes includes connecting elements called fittings.

Connecting elements

What are compression fittings for metal-plastic pipes? How to install them correctly? What to do if the connection starts to leak? You will learn the answers to these questions by reading the article.

Types, purpose, prices

Compression fittings are used for:

  1. Connections of water pipes of the same and different diameters.
  2. Plumbing branches.
  3. Additional equipment installations (filters, flasks, etc.)
  4. Changes in the direction of the water supply.
  5. Connections of a metal-plastic pipe with metal or plastic.

Depending on the purpose, they can be divided into types.

Corner metal

Used to change the direction of the pipeline. Elements with an angle of 90 and 120 degrees are in demand.

Angle metal fitting

In professional slang, corner elements are called bends, so this name is often used for metal corner fittings for metal-plastic pipes.

The corner element is used to connect a water pipe of the same diameter, it has a crimp fastener on both sides. There are branches for the metal-plastic system, in which there is a thread on one side, external or internal. Such elements are designed for corner connection with various equipment.

Another variety is water outlets. They have the form of an angle with a crimp fastening on one side and an internal thread on the other. Additionally, they have a platform with holes designed for rigid fixation with self-tapping screws.

Metal tees

Tees — types of fittings for metal-plastic water pipes, which are used to branch from the main pipe, connect taps or other elements.

metal tee


Depending on the version, it differs in the combination of fasteners. For example, two sides are a crimp fastener of the same diameter, the third is threaded or vice versa.

For the convenience of customers, the manufacturer marks the tees according to the size of the pipes or threads. As an example, consider the designation 20×1/2″x20. This is a tee, because there are three numbers in the designation, two ends of which are intended for installing a pipe, and the third has a thread. The diameter of the pipe for which the tee is intended is 20 mm, threaded connection ½ inch.


This type is designed to connect pipes of the same or different diameters. At the outputs it has a crimp mount.


The dimensions of the coupling depend on the diameter for which it is intended. The most common:

  • 20×16;
  • 20×20;
  • 32×16;
  • 32×20.

Couplings can be made with internal or external threads on one side. In this case, the marking will look like 16×3/4″. The first number is the diameter, the second is the thread size. Couplings with a threaded connection are used when it is necessary to switch from a metal pipeline to a metal-plastic one.



To connect the type of metal-plastic pipe — a collector, a special connecting fitting is used.

Connecting fitting

Depending on the type of collector, the version may differ. As a rule, the marking of the connecting fitting indicates the letter designation of the type of manifold for which it is intended. For example: EK — indicates that the element is used for manifolds with eurocone outlet.


Connecting element with four outlets. Outlet fasteners can be crimped or threaded, combined in different ways.

Cross connection

They are mounted like ordinary metal structures, except for cases when one of the outlets has a threaded connection. In such a situation, installation begins with a threaded connection.

Fittings by material

Connecting elements for pipes made of metal-plastic can be made of various materials. The most common are brass with a different coating. The coating is designed to protect the metal from corrosion and extend the life of the part. On sale you can find:

  1. Nickel-plated brass.
  2. Tin plated brass.
  3. Nickel plated brass with tin plating.
  4. Brass chrome plated.

Nickel-plated and chrome-plated brass options are popular.

There are also steel and copper, but they are less popular. Copper due to high price, steel due to low corrosion resistance and short service life.

Device and principle of operation


Structurally, a compression fitting consists of three parts: a base, a clamping nut and a compression ring (cone). The system works according to the collet principle, i.e. in the process of tightening the nut, it presses on the conical ring, which is compressed and securely presses the pipe to the base. It sounds complicated, but it’s actually much simpler. The base has a seat for a hose of a certain diameter. It has rubber pads. The diameter of the seat corresponds to the inner diameter of the hose, the nut has a hole equal to the outer diameter of the pipe.

Assembly order

The fitting is installed on a metal-plastic pipe according to a certain algorithm.

fitting installation

First, a nut is put on the pipe so that the thread is directed towards the base (joint). Next, a compression ring is put on. After that, the pipe is put on the seat. The ferrule is pushed towards the base of the fitting until it is possible to bait the clamping nut onto the threads. At the last stage, using an adjustable wrench, the nut is tightened to the stop.

Important! Over time, the pipe at the fitting installation site may begin to leak, to eliminate the leak, it is necessary to tighten the fitting.

Features of installing a threaded fitting

To connect a metal pipe with a metal-plastic pipe at an angle, a brass fitting with a threaded connection on one side is used. When installing such a fitting, there is a feature that must be considered. It is necessary to start the installation with the installation of a threaded connection, because. otherwise, the connection will fail.

It should be borne in mind that the threaded connection is not always tight, it is better to use sealants or fumlent to prevent leakage.

Another nuance that must be taken into account when installing a fitting is the quality of the edge (installation site) of the pipe. The butt should be straight cut, not bent or stretched.

Advantages and disadvantages of metal crimp connections


Compared to other types of connections, crimp designs have several advantages, the main of which is the possibility of reuse. Due to the fact that the design has a threaded connection and a clamping ring, it is possible to mount and dismantle the fitting almost endlessly.

The main malfunction that may occur due to frequent re-assembly is the rupture of the sealing gum. This is easy to fix by installing a new rubber band from a repair kit that is sold everywhere.

repair kit

The advantages include a high speed of assembly of connections, the possibility of combining. With the help of metal fittings, you can easily lengthen the pipe or repair it at the point of a rupture.

The disadvantage of metal fittings is that they are prone to corrosion. Over time, the connection will rust, rot, and may start to leak. In some cases, pulling the connection nuts will not help eliminate the leak, the fitting will have to be changed.

Another disadvantage of metal compounds is the condensate that accumulates on the surface. When installed in a cold water supply system in conditions of insufficient ventilation, condensate constantly accumulates on the surface, which can drain and accumulate in one place. This phenomenon can lead to a number of negative consequences that can be avoided when using other types of compounds.

Tools required for installation


Installation of metal-plastic pipes with metal compression fittings requires a minimum number of tools. In most cases, two wrenches are required, one for holding the base and one for the nut. In everyday life, it is convenient to use adjustable wrenches, because. they fit any fitting size. It is also necessary to have pipe scissors, with which it is convenient to cut and trim the edges.

Pipe shears

How to choose fittings

The choice of connecting elements for a water pipe depends on its design and specific location, therefore it should be carried out at the planning stage. Having a plan, it is easy to understand what fittings will be needed for the connection, determine the number of corners, diameter.

As a material, it is better to choose brass options, they are cheaper and more practical. If there is no cost limit, then copper can be used, they have a long service life and are resistant to temperature extremes.

In conclusion of the article, I would like to note that a large number of connections for plastic pipes are presented on the construction market, in which you can get confused and buy the wrong thing. Sales consultants who are familiar with the assortment and are familiar with the principles of installing fittings will help you choose the right one.


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