Contents
Modern plumbing is rarely made of metal. He has worthy competitors – polymers, which are gradually replacing him in many areas. One such material is low density polyethylene. Pipes for pressure pipelines are made from this material, that is, for water pipes and even for gas pipelines. This type of material is becoming increasingly popular, as the connection of polyethylene pipes is easy to do with your own hands. You just have to follow very simple rules.
Advantages and features of the application
Polyethylene pipes are made from low pressure polyethylene. This material is abbreviated as HDPE. It is characterized by increased strength and elasticity, has good performance properties:
- chemically neutral, can be used for food transportation;
- smooth walls prevent the formation of plaque inside;
- not subject to corrosion;
- low coefficient of thermal expansion – about 3% at maximum heating (up to + 70 ° C);
- they normally react to the freezing of water inside, due to elasticity they increase in diameter, and after thawing they take on their original dimensions.
One moment to remember! If you need pipes that are resistant to freezing (for example, for plumbing in a country house), look at the description or technical specifications when choosing. Not all types of copolymers that are used for the production of pipes tolerate freezing well. So be careful.
The main disadvantage of polyethylene pipes is the restrictions on the temperature of the transported medium: it should not be higher than + 40 ° C, that is, only cold water supply can be made from HDPE, they cannot be used for hot water and, moreover, heating.
Another point: polyethylene does not tolerate UV radiation. With constant exposure to the sun, the material loses its elasticity, and, after a while, breaks (some manufacturers make HDPE pipes resistant to ultraviolet radiation, but they are more expensive). Therefore, open laying of water pipes from plastic pipes is very undesirable. But it is very possible to lay a pipe in a trench from a well or well to the house, to make cold water distribution around the house. This is a fairly economical and convenient solution, since the installation and connection of polyethylene pipes is not a very complicated matter. If we are talking about a detachable connection, then no equipment is needed for it. All you need is fittings and hands.
Which polyethylene pipes are better
For the production of water pipes, two grades of polyethylene are used – PE 80 and PE 100. The hundredth polyethylene is denser and more durable than the eightieth. For water supply systems of a private house, the strength of PE 80 is more than enough – they can withstand pressure up to 8 atm. If you like a large margin of safety, you can take them from PE100. They work fine even at 10 atm.
What you should pay attention to is the country in which this product is produced. Quality leaders are European manufacturers. High precision execution guarantees high reliability of the system. Average quality and prices are from Turkish companies, in a cheaper price segment, Chinese manufacturers. Their quality, as usual, is also much lower. It is difficult to give advice here, everyone selects at their own discretion (or what is in the region).
Types of HDPE pipe connections
There are several types of connection of polyethylene pipes:
- detachable (on fittings or couplings);
- one-piece – by welding:
- using a special welding machine;
- electric couplings – a heater is built into such couplings, when an electric current is applied to it, polyethylene is heated and fused.
Weld mainly pipes of large diameters, which are used to create main pipelines. Pipes of small diameters – up to 110 mm, used in private construction, are mostly connected using fittings. Couplings are used more often during repair work, as their installation takes more time.
Fittings for polyethylene pipes are shaped parts (tees, crosses, angles, adapters, couplings), with the help of which the required system configuration is created. Since self-connection of polyethylene pipes is carried out more often with the help of fittings, let’s talk about them in more detail.
Assembly on compression (crimp) fittings
On one or two sides of the fitting (sometimes on three), a whole system is installed that provides the connection. The fitting itself consists of:
- housing;
- clamping nut;
- collets – a plastic ring with an oblique cut that provides a tight grip on the pipe;
- thrust ring;
- gaskets that are responsible for tightness.
What is a compression fitting for polyethylene pipes
How reliable is the connection
Despite the apparent unreliability, the connection of polyethylene pipes on compression fittings is reliable. Properly made, it can withstand operating pressures up to 10 atm and above (if these are products of a normal manufacturer). Watch the video for proof.
This system is good for easy self-assembly. You probably appreciated it already from the video. Just the pipe is inserted, the thread is tightened.
Summer residents, in addition to the ability to do everything with their own urks, like it because, if necessary, everything can be disassembled, hidden for the winter, and reassembled in the spring. This is in case the wiring is done for irrigation. The collapsible system is also good because you can always tighten the digging fitting or replace it with a new one. The disadvantage is that the fittings are bulky and internal wiring in a house or apartment is rarely made of them – the appearance is not the most pleasant. But for the water supply section – from the well to the house – it is difficult to find better material.
Assembly order
The pipe is cut strictly at 90 °. The cut should be even, without burrs. Dirt, oils or other contaminants are also unacceptable. Before assembly, chamfers are removed from the sections of the connected sections. This is necessary so that the sharp edge of the polyethylene does not damage the sealing rubber ring.
Spare parts are put on the prepared pipe in this order: a compression nut is pulled, then a collet, followed by a thrust ring. We install a rubber gasket in the fitting body. Now we connect the body and the pipe with the parts put on it, applying force – we must insert it all the way. We tighten all the spare parts to the body and connect them with a crimp nut. We twist the resulting connection of polyethylene pipes with force by hand. For reliability, you can hold out with a special mounting key. The use of other tightening tools is undesirable: plastic can be damaged.
Saddles and their scope
In addition to fittings, there is another interesting device that allows you to make branches from an already finished pipeline. These saddles are specially designed couplings. This coupling has one or more threaded holes. They usually put a tap in them, and a new branch of the water supply is connected to it.
Sedeki are put on the pipe, fixed with screws. After that, a hole is drilled in the branch with a drill and a thick drill in the surface of the pipe. When it is ready, a crane is installed, a branch is assembled further. So improve the system with minimal effort and cost.
Flange connections and transition to metal
In the water supply system, elements of the system that do not have a threaded, but a flanged connection can be installed. Usually these are taps or other shut-off or control valves. To connect with such elements, there is a special fitting for HDPE. On the one hand there is a standard compression version, on the other – a flanged version. Installation is standard – with a compression nut on one side, gaskets and bolts on the flange side.
When installing a water supply system from polyethylene pipes, questions may also arise about the connection of polyethylene and metal. For these cases, fittings are used, on one side of which there is a thread. It can be external or internal – it depends on the type of device or transition being installed. Such fittings are available in straight lines, in the form of a 90° angle.
The installation is standard – a thread (with winding neatly) on one side and a crimp nut on the other.