The main types of fittings for polypropylene pipes: characteristics, purpose and installation


A polypropy­lene pipe is active­ly used in the arrange­ment of heat­ing and water sup­ply sys­tems for pri­vate hous­es, apart­ments, enter­pris­es and oth­er facil­i­ties. Due to the fact that the pipe is sold in seg­ments of 2–4 m, for a strong tight con­nec­tion, indi­vid­ual seg­ments have to be weld­ed togeth­er. In addi­tion, it is nec­es­sary to take into account turns, branch­es, the tran­si­tion from polypropy­lene to met­al and oth­er nuances that will be encoun­tered in the work.

Fit­ting options indis­pens­able for the installer

A fit­ting will help solve these prob­lems. It is an ele­ment of a reli­able her­met­ic con­nec­tion, which already from the fac­to­ry is suit­able for spe­cif­ic needs. This is either a turn, or a con­nec­tion of two seg­ments, or a tran­si­tion from plas­tic to met­al, as well as tees, cou­plings, and oth­er options that are aimed at facil­i­tat­ing the work­flow and the pos­si­bil­i­ty of build­ing heat­ing and water sup­ply sys­tems of var­i­ous con­fig­u­ra­tions.

Specifications of polypropylene fittings

Under­stand­ing the tech­ni­cal aspects of a polypropy­lene pipe will allow you to install it cor­rect­ly. Fit­tings are also made of polypropy­lene, we can accept the same char­ac­ter­is­tics for most offers on the mar­ket as for pipes. Actu­al­ly, among the tech­ni­cal char­ac­ter­is­tics of mod­ern polypropy­lene pipes and fit­tings, there are:

  • Den­si­ty. This cri­te­ri­on allows achiev­ing high load resis­tance, low abra­sion over time, as well as hard­ness and frac­ture strength. The aver­age den­si­ty is 0.91 kg per cubic cen­time­ter.
  • Ther­mal con­duc­tiv­i­ty. Like a polypropy­lene pipe, the fit­ting does not form con­den­sate on the sur­face, due to the low coef­fi­cient of ther­mal con­duc­tiv­i­ty. That is why polypropy­lene pipes are con­ve­nient­ly mount­ed under the floor sur­face or in the walls, which adds addi­tion­al strength.
Sum­ma­ry table of tech­ni­cal char­ac­ter­is­tics of pipes and fit­tings
  • High strength. With prop­er sol­der­ing, we are guar­an­teed to get a reli­able con­nec­tion that will last us for many decades. The main thing is not to drill the con­nec­tion body, not to bend, not to sub­ject it to ten­sile loads. Mod­ern con­nec­tors eas­i­ly with­stand pres­sure up to 10 atmos­pheres of water.
  • Due to the chem­i­cal­ly inac­tive envi­ron­ment, the prod­ucts eas­i­ly tol­er­ate the impact of con­crete, plas­ter and oth­er fin­ish­ing mate­ri­als. Togeth­er with pipes, they can be used in enter­pris­es and fac­to­ries, in wet or too dry con­di­tions.
  • Tem­per­a­ture resis­tant. Here, it is worth tak­ing into account the type of liq­uid, as well as the use of con­nec­tors and turns indoors or out­doors. It is not rec­om­mend­ed that the con­nec­tion be exposed to neg­a­tive tem­per­a­tures, since under the expan­sion of water dur­ing freez­ing, polypropy­lene can eas­i­ly burst. The brit­tle­ness tem­per­a­ture is fixed at ‑5 to ‑15 degrees. Don’t for­get about wear and tear. The high­er the tem­per­a­ture of the car­ri­er, the less the prod­uct will last. It is believed that man­u­fac­tur­ers test polypropy­lene at tem­per­a­tures up to 40 degrees Cel­sius.
An exam­ple of prod­uct defor­ma­tion under high tem­per­a­ture


This implies anoth­er tech­ni­cal fea­ture, as a lin­ear expan­sion. Thanks to this cri­te­ri­on, the mate­r­i­al is stretched per meter by at least 10 mm, when oper­at­ing the coolant from 40 to 90 degrees Cel­sius.

Main types

Types of mod­ern fit­tings for polypropy­lene pipes are not always made only on the basis of this mate­r­i­al. There are com­bined mod­els that com­bine the tran­si­tion from plas­tic to met­al. There are vari­eties that involve the pres­ence of a damper, they are a faucet, which pro­vides con­trol over the oper­a­tion of a par­tic­u­lar water sup­ply cir­cuit. Accord­ing­ly, fit­tings may dif­fer in pur­pose, in the method of use and instal­la­tion. The fol­low­ing vari­eties can be dis­tin­guished on the mar­ket:

Some cou­pling options on the mar­ket
  • Cou­pling. This is an adapter designed to con­nect two pipes of the same or dif­fer­ent diam­e­ters. Accord­ing­ly, the tran­si­tion from plas­tic to met­al can be called a cou­pling, since it also allows you to con­nect two types of pipes. Cou­plings are char­ac­ter­ized by the pres­ence of a thread, a nut, an o‑ring, which is espe­cial­ly typ­i­cal for adapters from plas­tic to met­al.
  • Adapter. Here we are talk­ing about a polypropy­lene vari­ety, which, for exam­ple, on the one hand has a diam­e­ter of 32 pipes, on the oth­er, the diam­e­ter is under­es­ti­mat­ed, for exam­ple, 25 mm. Adapters are need­ed to nar­row the con­tour of the pipeline sys­tem, which allows you to cre­ate excess pres­sure in the cir­cuit.
  • Cor­ner. With a cor­ner, every­thing is clear. This option allows you to rotate the con­tour in the desired posi­tion. The angle is 90 and 45 degrees. Their diam­e­ters can be equiv­a­lent, that is, a 32-pipe entered the cor­ner, and a sim­i­lar one came out. It can be nar­rowed, which is just as eas­i­ly achieved with an adapter.
Amer­i­can — one of the many options on sale


  • Amer­i­can. With the advent of this con­nec­tion, installers were able to sig­nif­i­cant­ly facil­i­tate their work. Amer­i­can is a com­bi­na­tion of plas­tic and met­al. That is, it is a detach­able con­nec­tion, which is sealed with a rub­ber insert. It is con­ve­nient to install Amer­i­can women in detach­able sec­tions of a heat­ing and water sup­ply sys­tem, for exam­ple, at the instal­la­tion site of a cir­cu­la­tion pump, as well as when con­nect­ing a hydraulic accu­mu­la­tor.
  • A tee is an ele­ment of the sys­tem that is designed to divert a pipe in one part or anoth­er. Tees are active­ly used when con­nect­ing a radi­a­tor, as they allow you to pow­er this heat­ing ele­ment and con­tin­ue the sys­tem fur­ther. Like cor­ners, they can dif­fer in the diam­e­ter of the inlet and out­let holes.
Col­lec­tor assem­bled on the basis of polypropy­lene
  • A polypropy­lene man­i­fold is used to dis­trib­ute liq­uid in the main pipe. With prop­er dex­ter­i­ty, the col­lec­tors can be assem­bled inde­pen­dent­ly from tees, mak­ing the required num­ber of bends for your­self. A col­lec­tor of such a plan will be much cheap­er than the usu­al met­al col­lec­tor of a warm floor in a pri­vate house.
  • Cross. This ele­ment is con­ve­nient for unsol­der­ing boil­er rooms. The cross­piece has four out­lets, each of which is locat­ed at an angle of 90 degrees rel­a­tive to each oth­er.
  • Bypass. It is a means of tran­si­tion, which is impor­tant when equip­ping a boil­er room. Thanks to the bypass, you can bypass a hot or cold pipe with­out com­pro­mis­ing integri­ty. The pres­ence of such prod­ucts sig­nif­i­cant­ly saves the installer’s time dur­ing work.

Design, functionality, connection type and main diameters of a polypropylene fitting

Like a pipe, a fit­ting has a smooth sur­face on the out­side and inside. There­fore, it does not affect the through­put inside the closed loop. On each side of the fit­ting there is a round hole designed for the inlet and out­let of pipes, respec­tive­ly. If the prod­uct is com­plete­ly made on the basis of polypropy­lene, then before instal­la­tion it must be heat­ed using a spe­cial sol­der­ing iron, choos­ing the right tem­per­a­ture and heat­ing time. In the case of a com­bined option, for exam­ple, with an Amer­i­can, sol­der­ing is per­formed on one side, and thread­ed instal­la­tion is per­formed on the oth­er using a gas or plumb­ing key of the Croc­o­dile type.

Fit­ting in the pro­jec­tion “side” with the indi­ca­tion of the dimen­sions of the cor­re­spon­dence


Any fit­ting has a diam­e­ter, which is deter­mined in mil­lime­ters or inch­es. Among the most pop­u­lar sizes of fit­tings, mod­els for 20, 25, 32 and 40 mm can be dis­tin­guished. When work­ing with them, expe­ri­ence is impor­tant, since the heat­ing time of the fit­ting and pipe, depend­ing on the diam­e­ter, may be dif­fer­ent. For exam­ple, for a diam­e­ter of 20 mm, it is rec­om­mend­ed to hold 4–5 sec­onds, for 25 diam­e­ters 7–8 sec­onds, for 32 about 10–12. All this is indi­vid­ual, depend­ing on the man­u­fac­tur­er of the mate­r­i­al and the pow­er of the sol­der­ing iron. The spec­i­fied expo­sure time is rel­e­vant for the heat­ing tem­per­a­ture of the sol­der­ing iron of the order of 250–270 degrees.

As for the thread­ed con­nec­tion, when con­nect­ing to a met­al sec­tion of the sys­tem or installing equip­ment, it is impor­tant to achieve tight­ness. To do this, use flax and plumb­ing paste in the com­plex, fum tape and oth­er devices. Using flax, it is impor­tant to wind it in the direc­tion of the screwed nut, because oth­er­wise the tight­ness of the joint will be bro­ken.

Scope of a fitting from polypropylene

The main field of oper­a­tion of a fit­ting based on polypropy­lene is water sup­ply and heat­ing. Let’s look at an approx­i­mate heat­ing scheme for a small house. Sup­pose that we removed a 32 mm pipe from the boil­er room. To cre­ate excess pres­sure in the cir­cuit, it is nec­es­sary to nar­row the chan­nel, mak­ing the tran­si­tion from a diam­e­ter of 32 to 25 mm. To do this, you need to use a through fit­ting and, first, sol­der an adapter into it to a small­er diam­e­ter, and only then sol­der the main tran­si­tion. Sim­i­lar­ly, you can do it in the cor­ner of the room, so that after turn­ing a pipe of a small­er diam­e­ter goes.

Pos­si­ble prod­uct options for work

In order to make a tap to the bat­tery, you need a tee. The bat­tery is usu­al­ly con­nect­ed with a diam­e­ter of 20 mm, so again a tran­si­tion will be required. Cor­ners and con­tours will be involved here. The quan­ti­ty is cal­cu­lat­ed by the mas­ter indi­vid­u­al­ly for a spe­cif­ic draw­ing of the house.

In order to embed the cir­cu­la­tion pump into the heat­ing sys­tem of the house, you should use Amer­i­can women at the inlet and out­let of the equip­ment. They will also allow the instal­la­tion of cranes that will facil­i­tate the replace­ment of equip­ment in case of an unfore­seen repair. The Amer­i­can is used wher­ev­er you need to install detach­able equip­ment.

Pos­si­ble way to con­nect the cir­cu­la­tion pump to the heat­ing sys­tem


The tran­si­tion from plas­tic to met­al to the desired diam­e­ter is used both when con­nect­ing a radi­a­tor and when installing a water sup­ply cir­cuit. It is on the exter­nal thread of the tran­si­tion that a hose will then be wound, con­nect­ing the tap to hot and cold water.

The right choice of fitting by diameter — the main nuances of installation

The diam­e­ter of the fit­ting can be select­ed exact­ly by name. It is impos­si­ble to adjust the fit­ting in diam­e­ter by cham­fer­ing inside the prod­uct. When choos­ing, pay atten­tion to the pipe with which you work. It always has a mark­ing that shows the out­er diam­e­ter of the prod­uct. With­out heat­ing, the pipe will not enter the fit­ting, as heat­ing will help to remove the top lay­er.

If every­thing is clear with the choice of the diam­e­ter of the polypropy­lene part, then when choos­ing the thread diam­e­ter, you need to be care­ful. For exam­ple, a polypropy­lene plank with water out­lets, for the most part, comes with a ¾ inch inter­nal thread diam­e­ter. How­ev­er, there are options with a thread diam­e­ter of ½, which should be tak­en into account for spe­cif­ic equip­ment and see the cor­re­spon­dence table.

As for the tips, dur­ing the sol­der­ing of the fit­ting, as well as after fin­ish­ing work, you must adhere to the fol­low­ing rules:

  • After sol­der­ing, it is nec­es­sary to check by touch or visu­al­ly that the hole of the inner diam­e­ter of the chan­nel has not under­gone defor­ma­tion. Oth­er­wise, if there is a seal, the water in the sys­tem will pass with an obsta­cle, which will lead to a decrease in pres­sure in the cir­cuit.
  • If dur­ing sol­der­ing you over­ex­posed the fit­ting, and at the time when the con­nec­tion was made, it burst, it is rec­om­mend­ed to cut off the dam­aged part. It is for­bid­den to use a bro­ken fit­ting, espe­cial­ly if you are going to lay the water sup­ply under the screed or into the wall.
  • After weld­ing of the water sup­ply or heat­ing cir­cuit is com­plet­ed, it is rec­om­mend­ed to per­form a pres­sure test and check how well the cir­cuit holds the set pres­sure. This is impor­tant before pour­ing the floor screed if the pipe is hid­den.
  • Try to use fit­tings and pipes from the same man­u­fac­tur­er. Still, the com­po­si­tion of polypropy­lene, for bet­ter weld­abil­i­ty of the mate­r­i­al, should be the same.
  • To prop­er­ly posi­tion the fit­ting rel­a­tive to the plane in which it will lie, try on and mark with a pen­cil in the form of stripes. After heat­ing, we sim­ply join the notch­es. When sol­der­ing, make a notch on the pipe to a depth of 1.5 cm so that when it is pressed into the fit­ting, you do not pass or clog the hole inside.
  • Observe the tem­per­a­ture regime of the sol­der­ing iron, do not over­ex­pose the fit­ting when heat­ed, mon­i­tor its appear­ance and the absence of fac­to­ry dam­age.


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