A major overhaul of an apartment or a private house can often be associated with a complete or partial replacement of water pipes. In older buildings, they are most often metal, but now, as a rule, polypropylene products are on the market. Therefore, the owner is faced with the question of how to connect polypropylene pipes with metal pipes?
When may it be necessary to connect a polypropylene pipe with a metal one?
Such a need may arise both during the repair and modernization of an existing pipeline, and during the construction of a new one. You can’t do without connecting polypropylene pipes with metal pipes in the following cases:
- work of several contractors at one facility, their uncoordinated actions and the use of pipes from different materials;
- presence of metal leads of household and industrial equipment;
- partial replacement of emergency communications;
- the need to connect the pipeline to the processequipment that operates at a critical temperature for polypropylene pipes;
- laying of main pipeline routes, which in the future will be subject to increased mechanical and thermal stress.
The reasons for the need to connect pipes from different materials are different, therefore, the method of joining should be selected optimally to the existing conditions.
Features of the use of metal and polypropylene pipes, their differences
The operational characteristics of the pipeline directly depend on the metal used for its manufacture. Most often it is:
- Cast iron, from which communications are made in buildings erected in Soviet times. The material is fragile, the pipe can be broken with a strong hammer blow.
- Steel is susceptible to corrosion, and dirt and various impurities can accumulate on the inside of such pipes.
- Stainless steel, which is the most expensive but difficult to process material with a long service life.
- Galvanized steel - difficult to install, but made up for by excellent performance.
Despite the strong differences, the connection of polypropylene pipes with metal pipes can be easily performed. But when choosing, it should be borne in mind that polypropylene pipes are not resistant to high temperatures (the boundary value is a temperature of +80°C) and their differences. Therefore, most often such a pipeline is installed only in residential premises.
Types of connections
To connect polypropylene pipes with metal pipes, two types of connections are used:
- Threaded docking. For this type of connection, a special adapter is used - a threaded coupling. It is suitable for working with pipes with a diameter of less than 40 mm. In this case, fittings having a different design are used. This part is an adapter from a metal pipe to a polypropylene one, which has a thread on one side for fastening a metal pipe, and on the other, a smooth sleeve for a polypropylene one. If necessary, the shape of the fitting can be changed by heating it with a building hair dryer to a temperature of +140 °C. Also on sale are fittings for connecting pipes of different lines, for bending and turning.
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Flange connection. This type of connection is selected when large diameter pipes are used. A feature of this design is the possibility of disassembling it if necessary. The flange is a collapsible part, consisting of a sleeve for a metal pipe, a cap part for the transition to plastic and a set of bolts.
Flange for metal and polypropylene pipes - Threadless coupling. This clutch consists of several parts:
- steel or cast iron body;
-two nuts located on both sides of the body;
- four metal nuts inside the coupling cavity;
- rubber pads that serve as seals (their number may vary).
Required tools and materials
Before direct work, it is necessary to prepare tools and consumables. To connect polypropylene pipes with metal pipes you need:
- polypropylene pipes of the required diameter;
- 90° and 45° corners;
- clips for fixing polypropylene pipes on the wall;
- drill;
- grinder with discs for metal;
- thread cutter - a tool for cutting threads on metal pipes, the set includes a functional part, which is a round frame in the form of a short cylinder, a set of dies or die cutters, holders, clamps, pliers and other similar tools may additionally be present;
- fum tape;
- tow;
- silicone sealant;
- couplings (most commonly used American 1/2), fittings, flanges;
- special plastic scissors;
- roulette;
- construction pencil;
Technology for connecting polypropylene pipes with metal pipes
You can do all the work yourself. In this case, you first need to carefully select all the elements of the future design. It is also recommended to study the advice of experts:
- do not overtighten the bolts and nuts, as this can lead to cracks in the polypropylene;
- you need to make sure that there are no burrs and sharp elements on the part of the fittings for metal pipes, as they can cause damage to polypropylene structures (if such defects are found, the surface must be cleaned with a file);
- when upgrading the heating system, it is recommended to replace rubber gaskets with silicone ones.
Installation of threaded fittings
To do this job you need to follow the instructions:
- Remove the existing coupling from the metal part of the communication. If this was not possible, then you can simply cut off a piece of pipe, then apply grease to the saw cut, and then use a thread cutter to make a new thread.
- Wipe the threads of the fitting for metal pipes with a rag, place fum-tape or tow on top, and then cover with a layer of silicone sealant. You need to lay the sealant along the thread.
- Screw on the fitting. Using a key in this case is not recommended, as there is a risk that this part will crack due to excessive force. You can tighten the fitting for water pipes after turning on the system.
This method is most effective when installing pipes of different materials on bends and bends.
When using this type of pipe connection, it should be remembered that polypropylene products are able to expand when exposed to temperature (for example, if a heating system was installed). This means that when pipes are located under a layer of plaster, it is recommendedleave a gap of 1 cm using tubular insulation. This is especially true for places around bypasses and tees.
Using flanges
Flange mounting technology is simple. To connect pipes you need:
- Cut off the metal tube at the place of the future connection. The cut should be as even as possible, for which you can use a grinder.
- Put the flange on this part, then install the rubber gasket. The last part will act as a seal.
- Push the flange over the rubber gasket.
- Perform similar actions with a polypropylene pipe.
- Connect the two flanges with suitable bolts. This should be done evenly and alternately, while it is recommended to ensure that there are no distortions and displacement of parts. Don't push too hard.
Using a threadless coupling
First you need to prepare gaskets, washers and nuts, which must correspond to the cross section of the pipeline elements. After that, you can proceed with the installation of the coupling without thread according to the following instructions:
- Through the nuts, through the spacers and washers, insert the metal and polypropylene pipes into the coupling from both sides.
- Tighten the nuts to the stop, while making sure that the gaskets are clamped to the stop.
Such a connection, subject to the technology, will be durable and strong.
You can join the elements of the pipeline yourself. To do this, you need to choose parts of the right size, withthis should definitely take into account the diameter of the pipes (metal and polypropylene pipes at the same time, since there are connecting elements with different connectors on both sides), prepare the tool and follow the instructions. A test run of the system will help determine the quality of the connection.
