How to install metal-plastic pipes with compression fittings


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 20x1/2″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:

  • 20x16;
  • 20x20;
  • 32x16;
  • 32x20.

Cou­plings can be made with inter­nal or exter­nal threads on one side. In this case, the mark­ing will look like 16x3/4″. 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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