Welding (soldering) of polypropylene pipes

More and more often, metal pipes are replaced with plastic ones, in particular, made of polypropylene. They have a long service life (up to 50 years), do not rust, do not rot, weigh a little, and you can also assemble everything with your own hands, without involving specialists. Welding polypropylene pipes requires some skill, but it comes quickly. You can first practice on small scraps and inexpensive fittings, and then move on to creating more serious things. 

Types and purpose

Polypropylene pipes are available in four colors – green, grey, white and black. Only black ones differ in characteristics – they have increased resistance to ultraviolet radiation and are used when laying an irrigation system on the ground. All the rest have similar characteristics and are laid indoors or buried in the ground.

By appointment, polypropylene pipes are of the following types:

• For cold water (temperature up to +45°C). It is easy to distinguish them by the longitudinal blue stripe.
• For hot water supply (heating up to +85°C). A distinctive feature is a red stripe.
• Universal (maximum heating up to +65-75°C depending on the manufacturer). Two stripes are applied side by side – blue and red.
  

For both cold and hot water, there are pipes with different characteristics. This is displayed in the label:

• PN10 are used exclusively in cold water supply systems (up to +45°C) with low pressure (up to 1 MPa). They have a small wall thickness. Not suitable for high rise buildings.
• PN16. Often labeled as universal, but more often used for cold water – they withstand heating of the medium up to + 65 ° C and pressure up to 1,6 MPa.
• PN20. Thick-walled pipes, which can transport medium with temperatures up to +80°C, withstand pressures up to 2 MPa. Used in the distribution of hot water and heating systems.
• PN25. These are reinforced polypropylene pipes (foil or fiberglass). Due to the presence of a reinforcing layer, they often have a smaller wall thickness than PN20. Medium heating temperature – up to +95°C, pressure – up to 2,5 MPa. They are used for hot water supply and heating.

All of them are produced in different diameters – up to 600 mm, but in apartments and private houses they are mainly used in sizes from 16 mm to 110 mm. Please note that the inner diameter is indicated, as the wall thickness may vary.

What is welding of polypropylene pipes

Polypropylene is characterized by increased rigidity, and fittings from the same material are used to create systems of the required configuration. These are various angles, tees, bypasses, adapters, couplings, etc. They are connected to pipes by soldering. This process is also called welding, but its essence does not change: two elements are heated to a melting point and, in a hot state, are connected to each other. When done correctly, the connection turns out to be monolithic and serves no less than the pipes themselves.

To connect polypropylene with metals, there are combined fittings in which one part is made of metal and is connected using a threaded connection, and the second – polypropylene – is welded.

How to solder

Polypropylene pipes are welded using a special device called a soldering iron or a welding machine. This is a small metal platform, inside of which there is an electric coil that heats up the surface. Because of this design, this unit is also called an iron.

To connect two elements, the spliced ​​surfaces are heated to a melting point (+260°). To heat the element to the desired depth, two different Teflon-coated metal nozzles are installed on the welding platform:

• a mandrel (smaller diameter) is used to heat the inner surface;
• a sleeve is placed to heat the outer surface.
  

Two elements to be connected are simultaneously put on the corresponding nozzles, held for a certain period of time (several seconds), then connected. This is how polypropylene pipes are welded.

How to weld

The designs of soldering irons for polypropylene pipes are slightly different, but the principles of working with them are common. There are two main models – with a flat platform or a cylindrical heater. With normal quality, both work, there is practically no difference. Whoever is more comfortable, then choose.

Preparatory work

Before starting work, you need to warm up the soldering iron, but everything is not so simple here. The order of its preparation is as follows:

• First, nozzles of a suitable diameter are installed on the platform.
  • A stud is threaded into the hole in the platform, a mandrel and a sleeve are put on it from both sides, tightened with nuts from both sides.
  • If the heating element is in the form of a tube, nozzles for it are sold fixed on a plate. The plate is put on the heating element, the fixing bolt is tightened.
• The required heating temperature is set on the regulator. For polypropylene pipes, the welding temperature is +260°C. We put it on the regulator, turn it on.
• We are waiting for the signal to set the set temperature. In some models there is a sound signal, but, basically, the LED lights up or goes out (in different models in different ways).

The soldering iron is ready to work. But you still need to prepare pipes and fittings. The first condition for high-quality welding is an even cut. The cut must be strictly vertical, without burrs and rips. Such a cut can be obtained using special scissors. They have two wide jaws on the bottom that hold the pipe in place, and the cutting part is on top.

The second condition for good soldering of PP pipes is clean, dry, fat-free parts. If you want plumbing or heating to serve for a long time and not flow, you should not skip this procedure. The pipe cut and fitting are cleaned with alcohol or water and dishwashing detergent. Then they wait until everything is dry, and only after that they begin the soldering process.

How long to heat

When welding, polypropylene must be heated strictly to the required temperature. Overheating and underheating significantly reduce the quality of the seam. An overheated and softened pipe simply will not fit into the fitting, and an insufficiently heated material will not fuse.

The heating time depends on the diameter of the pipes, the air temperature and is indicated in the table.

In general, soldering is possible at +5°C, but the data are given for +20°C. In hotter weather, the exposure time of the elements on the soldering iron is reduced by 30-60 seconds, in colder weather it is increased.

Pay attention to the column “depth” of welding in the table. This mark is placed on the pipe. Before it, you will need to press it into the fitting. This creates a small bead of molten plastic in front of the fitting edge. This will mean that the seam is made correctly.

Another column needs clarification – “welding time”. This is the time for which it is necessary to squeeze and fix the elements to be welded.

In general, if you try to insert a cold pipe into a fitting, it should go in with great difficulty – the outer diameter of the pipe is slightly larger than the inner diameter of the fitting. This is done intentionally, to provide some excess material, from which the roller on the seam is formed. In order for the welding of polypropylene pipes to be reliable, it is better to take all the components from the same company. This ensures that the sizes match. Otherwise, it is necessary to try on – so that the fitting does not “slip”, but is pulled with difficulty.

Technology

As already mentioned, when welding polypropylene pipes, they and fittings must be cleaned, degreased and dried. And only after that you can start soldering.

This preparation is suitable for all types of pipes, except for foil-reinforced ones. In this case, after the desired piece has been cut off, the cut is cleaned to the foil with a special device – a shaver. A pipe is inserted into it and rotated several times. In this case, the top layer of plastic is removed, after which it can be degreased and soldered.

After the surface dries, a mark is drawn on the pipe, marking the distance to which it must be pressed into the fitting (the easiest way is with a thin marker or a sharply honed simple pencil).

Soldering polypropylene step by step

Further, the technology for welding PP pipes is as follows:

• We put the cut section of the pipe on the mandrel, insert the fitting into the sleeve. This must be done at the same time, in extreme cases, the fitting is put on earlier, as it has a large wall thickness. The delay should be very small.
  

• We withstand the elements for the required amount of time.
• We remove from the nozzles, connect by pressing the pipe into the fitting to the mark. The connection is exclusively linear, you can not rotate the elements relative to the horizontal axis (do not twist, although you really want to). It is possible to align the horizontal immediately after the connection, if a discrepancy is noticed.
  

• When connecting, you have to make quite a lot of effort. The same force is maintained for several seconds (in the table in the “welding time” column).
• After the specified time has elapsed, we stop pressing, and the connection cannot be disturbed for several minutes (column “cooling time” in the table). After that, we can assume that the soldering of the polypropylene pipe is completed. You can move on to the next stitch.

One note: immediately after welding, inspect the nozzles on the soldering iron. If there is material residue, it can be removed with a soft, lint-free, non-fading (white) cloth. You can’t leave plastic on the soldering iron – the next fragment will stick, it will be difficult to tear it off. You can not clean the nozzles with the use of abrasives – they have a Teflon coating, they scratch easily. And even microscopic scratches will cause the fragment on the soldering iron (iron) to stick.

By the way, it is better to work in cotton gloves – there will be fewer burns.

Before putting the system into operation, it must be checked. They do this by pressing. What it is and how to do it, read here. 

Distribution of polypropylene pipes

Polypropylene pipes are used for mounting a comb of cold or hot water, heating. The choice of diameter in each case is individual – it depends on the volume of liquid that needs to be pumped per unit of time, the required speed of its movement (the formula in the photo).

Calculation of pipe diameters for heating systems is a separate issue (the diameter must be determined after each branch), for water pipes everything is easier. In apartments and houses, pipes with a diameter of 16 mm to 30 mm are used for these purposes, with the most popular ones being 20 mm and 25 mm.

We consider fittings

After determining the diameter, the total length of the pipeline is considered, depending on its structure, fittings are bought in addition. With the length of the pipes, everything is relatively simple – measure the length, add about 20% for the error and possible marriages in the work. A piping diagram is required to determine which fittings are needed. Draw it, indicating all the taps and devices to which you want to connect.

To connect to many devices, a transition to metal is required. There are also such polypropylene fittings. They have a brass thread on one side, and a regular solder fitting on the other. Immediately you need to look at the diameter of the pipe of the connected device and the type of thread that should be on the fitting (internal or external). In order not to be mistaken, it is better to write everything down on the diagram – above the branch where this fitting will be installed.

Further, according to the scheme, the number of “T” and “G” figurative compounds is considered. For them, tees and corners are bought. There are also crosses, but they are rarely used. Corners, by the way, are not only at 90 °. There are 45°, 120°. Do not forget about couplings – these are fittings for joining two pipe sections. Do not forget that polypropylene pipes are completely inelastic and do not bend, so each turn is done using fittings.

When you purchase materials, agree with the seller on the possibility of replacing or returning part of the fittings. Problems usually do not arise, since even professionals cannot always immediately determine exactly the required assortment. In addition, during the installation process, sometimes it is necessary to change the structure of the pipeline, which means that the set of fittings changes.

Polypropylene has a fairly significant coefficient of thermal expansion. If a polypropylene hot water supply or heating system is being installed, it is required to make a compensator, with which the lengthening or shortening of the pipeline will be leveled. This can be a factory-made compensator loop, or a compensator assembled according to the scheme from finigs and pieces of pipes (pictured above).

Ways of laying

There are two ways to install polypropylene pipes – open (along the wall) and closed – in strobes in the wall or in the screed. On the wall or in the strobe, pipes made of polypropylene are mounted on clip holders. They are single – for laying one pipe, there are double – when two branches run in parallel. They are fastened at a distance of 50-70 cm. The pipe is simply inserted into the clip and held due to the force of elasticity.

When laying in a screed, if it is a warm floor, the pipes are attached to the reinforcing mesh, no other additional fastening is required. If the connection to the radiators is monolithic, the pipes can not be fixed. They are rigid, they do not change their position even when filled with coolant.

The nuances of soldering

The process of welding polypropylene pipes, as you have seen, does not leave much work, but there are a lot of subtleties. For example, it is not clear how, when joining pipes, to adjust the sections so that the pipes are exactly the length that is required.

Another point of welding polypropylene pipes is soldering in hard-to-reach places. It is not always possible to put a pipe and a fitting on the soldering iron on both sides. For example, soldering in the corner. Soldering iron, you have to put it in a corner, on one side the nozzle rests directly against the wall, you can’t pull the fitting on it. In this case, a second set of nozzles of the same diameter is installed and the fitting is heated on it.

How to solder polypropylene pipes in a hard-to-reach place

How to switch from iron pipe to polypropylene.