The main types of fittings and their characteristics, clamping and fastening


Pipelines ensure the ful­fill­ment of domes­tic and indus­tri­al needs of the pop­u­la­tion. How­ev­er, to cre­ate them, you will need to use only proven and high-qual­i­ty fas­ten­ers. In order not to lose in the choice, most experts try to study the full range of fit­tings.

Fig 1. Fit­tings

Technical specifications

Fit­tings are clas­si­fied based on tech­ni­cal cri­te­ria:

  • To per­form what tech­ni­cal role is required to install fas­ten­ers — fit­tings;
  • What mate­r­i­al is the struc­ture made of?
  • How will the mount be fixed;
  • Dis­tinc­tive design fea­tures and size.

The size range starts from 4 — 600 mm and depends on the direct pur­pose (con­nec­tion of brake-type hoses or in the prepa­ra­tion of the main pipeline). It is cus­tom­ary to dis­tin­guish sev­er­al stan­dard sizes of fit­tings: 20, 25, 50, 110 and 32mm. As a rule, due to the great pop­u­lar­i­ty, such mod­els will not be dif­fi­cult to find.


For com­pe­tent and high-qual­i­ty instal­la­tion of plumb­ing, it is impos­si­ble to do with­out con­nect­ing ele­ments. The basis is often durable met­al — steel, cast iron, met­al, brass. No less com­mon are con­struc­tions made of plas­tic and syn­thet­ic mate­ri­als: polyvinyl chlo­ride, polypropy­lene, poly­eth­yl­ene.

Con­sid­er­ing the diverse device of the fit­ting sys­tem for heat­ed tow­el rails, sev­er­al options can be dis­tin­guished:

  1. Thread­ed con­nec­tion

    Fig 2. Thread­ed
  2. Com­pres­sion.
  3. With cap­il­lary sol­der­ing.
  4. Press.
  5. Self-lock­ing.

To build a reli­able water sup­ply, sev­er­al types are used at once:

  • If the sec­tion is straight, the clutch is rel­e­vant;
  • If the sys­tem is branched — a tee or a cross;
  • To change the direc­tion of flow — branch.

What are the connections

The choice of design depends pri­mar­i­ly on the mate­r­i­al of the water pipes, the diam­e­ter. Among the most pop­u­lar are thread­ed, weld­ed, com­pres­sion, col­let. In order to con­nect a pipe cor­ru­gat­ed from stain­less steel with high qual­i­ty and with­out leaks, the brass look is best suit­ed, where there are addi­tion­al sil­i­cone seal­ing ele­ments.

To con­nect the pipe to the ele­ment, a fit­ting must be present at one end, and a cou­pling must be screwed into the oth­er. This is nec­es­sary to achieve max­i­mum fix­a­tion in the struc­ture. In prac­tice, “moth­er” is called the type of con­nect­ing ele­ment, made as a cou­pling, and “dad” — in the form of a fit­ting.

It is impor­tant to take into account that designs using these types of con­nec­tions are rel­e­vant with a small and medi­um cross-sec­tion­al diam­e­ter, where the diam­e­ter is more than 50mm. Weld­ing or con­nec­tion by means of flanges is used.

Fig 3. Steel struc­tures


If you need to con­nect radi­a­tors, it is rec­om­mend­ed to use a straight or angled Amer­i­can. When the pipeline is planned to be laid for out­build­ings or house­hold build­ings, when orga­niz­ing heat­ing or a sew­er sys­tem, it is rec­om­mend­ed to use sys­tems with adhe­sive, weld­ing or thread­ed types of con­nec­tions.

To cre­ate a ven­ti­la­tion sys­tem, addi­tion­al seals are not required. Ide­al for sealants. To con­nect the hoses, it is most rel­e­vant to use thread­ed fit­tings.

As a rule, when an arti­fi­cial irri­ga­tion sys­tem is cre­at­ed, pipes made of plas­tic or oth­er syn­thet­ic mate­r­i­al are used. Pro­fes­sion­als use shut­off valves (faucets, valves, gate valves) or tees, cou­plings. It is actu­al to choose a diam­e­ter in the range of 20–25mm.

When cre­at­ing a pneu­mat­ic sys­tem, it is impor­tant to pay atten­tion to the con­di­tions in which oper­a­tion is planned. As a rule, con­nect­ing ele­ments made of poly­mer­ic mate­r­i­al, stain­less steel, cop­per alloys are suit­able.

For radi­a­tors, a 90, 45 degree elbow and fit­tings are used. Most often they are equipped with stain­less steel threads. Brake hoses are also not com­plete with­out mod­els that ensure the tight­ness of the struc­ture. They are pre­sent­ed in var­i­ous diam­e­ters: 4–18mm. The design retains strength ‑50 to +100 degrees. The opti­mum pres­sure is 12 bar.


Types of fit­tings are deter­mined depend­ing on the para­me­ter in ques­tion, so famil­iar­ize your­self with sev­er­al clas­si­fi­ca­tions at once. Depend­ing on the mate­r­i­al used, there are:

  1. Stain­less. When cre­at­ing, stain­less steel is used. Among the main fig­u­ra­tions, it is worth high­light­ing tees, cross­es, bends, tran­si­tions. The most com­mon type is thread­ed.
  2. Bronze. Dif­fers in big ser­vice life. They are ver­sa­tile and can be used in con­junc­tion with pipes made of steel, plas­tic or cop­per.
  3. Met­al. In pro­duc­tion, only fer­rous met­als (steel, cast iron) or non-fer­rous met­als (bronze, brass or cop­per) are used.
  4. Cast iron. Belongs to the thread­ed cat­e­go­ry. Opti­mal for cre­at­ing sealed struc­tures using seals.
  5. Chrome plat­ing is often used to improve the per­for­mance of fas­ten­ers. They can be used with pipes of var­i­ous mate­ri­als.

The sec­ond type of clas­si­fi­ca­tion involves the divi­sion of fist­ing accord­ing to the design fea­tures:

  1. DKO with met­ric straight thread. In the sub­cat­e­go­ry, it is cus­tom­ary to sin­gle out straight, angu­lar struc­tures of 45 or 90 degrees.
  2. For straight sec­tions, a straight con­struc­tion is used.
  3. To cre­ate a sealed struc­ture, the con­nect­ing fit­tings are crimped using two spe­cial rings. The design avoids leaks over time.
  4. Push fit­ting. Visu­al­ly it con­sists of a seal in the form of a ring, a cou­pling and a fer­rule. No addi­tion­al press tools are used for cre­ation. Rel­e­vant for the cre­ation of heat­ing sys­tems or water sup­ply.
    Fig 4. Push

    Fig 5. PUSH device
  5. Bag­gio. Visu­al­ly, the design does not imply any dif­fi­cul­ties. There is a body, rings with seals and thread­ed bolts. You can also find straight or at angles of 45 and 90 degrees. Suit­able for cre­at­ing a con­trol sys­tem for machines 6–25mm

    Fig 6. Bag­gio
  6. A con­tain­er con­nec­tion will be required to install con­tain­ers of var­i­ous ori­en­ta­tions.

The third clas­si­fi­ca­tion sys­tem is built accord­ing to the type of con­nec­tion:

  1. col­let. Belong to the cat­e­go­ry of crimp. Experts do not advise using them to con­nect pipes made of PVC mate­r­i­al, since there is a high prob­a­bil­i­ty of caus­ing seri­ous mechan­i­cal dam­age.
  2. With the inclu­sion of a union nut, it presents a split view. Actu­al to car­ry out the dis­man­tling of pipes with­out the need to addi­tion­al­ly cre­ate rota­tion.
  3. Air is referred to as a quick-release type. Ide­al for cre­at­ing pneu­mat­ic sys­tems. Used in the man­u­fac­ture of plas­tic or met­al.
  4. Hydraulic — the main rep­re­sen­ta­tive of thread­ed or crimped con­nec­tions.
  5. Amer­i­can is made from var­i­ous types of mate­ri­als.
  6. To work with poly­mer pipes, elec­tric weld­ed struc­tures are the most rel­e­vant. Over­lap­ping or end-to-end instal­la­tion is allowed.


The last clas­si­fi­ca­tion implies the type of pipe con­nec­tion:

  1. Polypropy­lene. Rel­e­vant when cre­at­ing hot or cold water sup­ply. They can cre­ate a com­bined ver­sion using brass inserts.

    Polypropy­lene struc­tures
  2. Pneu­mat­ics with steel, cop­per fit­tings, bronze or brass poly­mers. Suit­able for pipes made of polypropy­lene.
  3. Poly­eth­yl­ene with lay­ing of elec­tric heat­ing ele­ments. As a rule, a heat­ing wire is used. With its help, reli­able weld­ing of the con­nect­ing ele­ment and the pipe is car­ried out.

  4. With high pres­sure rel­e­vant for hydraulics. The sys­tem trans­ports flu­id.

Scope of various connections for polyethylene pipes

The under­ly­ing mate­r­i­al is poly­eth­yl­ene with dif­fer­ent den­si­ties or brass. The diam­e­ters of the fit­tings used are used in vari­a­tions of 20–1200mm. To get acquaint­ed with all types and char­ac­ter­is­tics, you can refer to the fol­low­ing table:

View Char­ac­ter­is­tics and scope
com­pres­sion It is used in the cre­ation of a drink­ing water sup­ply sys­tem. Resis­tant­ly tol­er­ates tem­per­a­ture con­di­tions in the range of 0 + 45 degrees, pres­sure 10–16 bar. Weld­ing is used dur­ing instal­la­tion
Elec­trow­eld­ed Using the heat­ing ele­ment as a wire. Finds appli­ca­tion in the man­u­fac­ture of gasi­fi­ca­tion sys­tems
Met­al Suit­able if there are addi­tion­al ele­ments from oth­er mate­ri­als
cast The man­u­fac­tur­ing sys­tem is iden­ti­cal to the HDPE sys­tem, the tem­per­a­ture is 0–40 degrees
Seg­ment (weld­ed) It is made from sep­a­rate seg­ments that are con­nect­ed into a sin­gle sys­tem. The part for the con­nec­tion must allow the orga­ni­za­tion of branch­ing when cre­at­ing a water sup­ply sys­tem
Brass Dif­fers in reli­a­bil­i­ty and tight­ness. Actu­al use in con­junc­tion with bush­ings, reduces the risk of defor­ma­tions, when using a com­pres­sion fit­ting, it allows to nar­row the pipe diam­e­ter
75mm HDPE pipe Rel­e­vant for cre­at­ing a non-pres­sure sew­er sys­tem
Fig 9. Elec­tric weld­ed

How to choose the best PP option


In order not to make a mis­take and choose the best fit­tings, it is rec­om­mend­ed to take into account the mate­r­i­al from which the con­nec­tion is made and its diam­e­ter for:

  1. orga­ni­za­tion of sol­id struc­tures made of cop­per or steel — flanges. They are suit­able if it is impos­si­ble to avoid weld­ing or the com­po­nents are thread­ed. When order­ing a batch, you need to con­sid­er how flat they are, whether the ends are per­pen­dic­u­lar. From these indi­ca­tors depends on how tight the con­nec­tion will be. To achieve tight­ness, it is bet­ter to use a spe­cial FUM tape. The lock­nut will help to achieve opti­mal fix­a­tion of the seal made of var­i­ous met­als (cast iron, steel or bronze).
  2. solv­ing plumb­ing prob­lems, it is bet­ter to select con­nect­ing ele­ments from the same mate­r­i­al as pipes. As a rule, it is PVC. Sol­der­ing is car­ried out with spe­cial tools. It is impor­tant to take into account that such mod­els are char­ac­ter­ized by high cost.
  3. sys­tems with met­al-plas­tic present, it is bet­ter to use sev­er­al fas­ten­ers, on aver­age 3–4. When order­ing them, it is impor­tant to con­sid­er the weight. As a rule, the bet­ter the design, the more it weighs.

It is not rec­om­mend­ed to save on the pur­chase of con­nect­ing ele­ments, since the like­li­hood of seri­ous leaks and pipe defor­ma­tions depends on them. This is espe­cial­ly true for sys­tems that must with­stand high pres­sure.

The pop­u­lar­i­ty of poly­mer mod­els, which dif­fer from the above cat­e­gories in ease (you can install it your­self with­out the help of a team of pro­fes­sion­als), the dura­tion of oper­a­tion (an aver­age of 30–40 years with­out replace­ment), it is allowed to cre­ate water sup­ply sys­tems of var­i­ous lev­els of com­plex­i­ty. How­ev­er, it is also nec­es­sary to take into account the specifics of the planned work and the mate­r­i­al from which the pipes are made and their diam­e­ter in order to ensure tight­ness and max­i­mum tight­ness of the joints.


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