Low pressure polyethylene (HDPE) pipes

Recommendation points

• Varieties of HDPE pipes
• Behavior for outdoor, underground and indoor installation
• Range of fittings and valves for HDPE pipes
• Installation of main water supply systems
• Use in rough plumbing

The introduction of polymer materials turned out to be most obvious in the example of plumbing systems. Today we will tell you in detail about polyethylene pipes: what they are, what are good, in what they are superior to other types, and most importantly – how to work with HDPE pipes yourself.

Varieties of HDPE pipes

Low-pressure polyethylene (HDPE) pipes are perhaps the most durable way of laying communications for transporting liquids or gases. In addition to their complete immunity to most chemical reagents, the main advantages are also high resistance to compression, almost complete absence of sedimentary deposits on the inner walls and low hydrodynamic resistance.

1. HDPE pipe for a gas pipeline. 2. HDPE pipe for cold water supply

It is not always clear to the end consumer what is the difference between different types of HDPE pipes: they are all equally black and, at first glance, seem to be universal in use. Closer acquaintance reveals a longitudinal color stripe: blue for pumping liquids and yellow for gas pipelines. There are also colorless pipes, which are used, as a rule, as technical embedded channels and protective shells, including for pipes of the first two types. The main differences between pipes without color marking are the impossibility of their work under pressure and the use of secondary raw materials in the manufacture.

As for the standard sizes, today manufacturers support the entire running range with an equivalent throughput diameter of 16, 20, 25, 32, 40 mm and up to 200 and 300 mm pipes for use in water mains and heating mains. For each of the standard sizes, the SDR standard – a numerical factor – determines the ratio of the outer diameter to the wall thickness.

Behavior for outdoor, underground and indoor installation

HDPE pipes demonstrate the highest known versatility. Regardless of the environment in which they are located, complete chemical inertness and the absence of any emissions during operation are demonstrated. The operating temperature range for common-use pipe brands is from -60 to + 40-60 ° С.

Compared to PPR, polyethylene pipes exhibit low heat resistance. When the upper mark of the temperature range is reached, a pronounced linear expansion is observed. When overheated, the pipe wall loses its rigidity and, at high operating pressure, can irreversibly change its shape. Therefore, the use of polyethylene pipes in heating and hot water systems is excluded. In terms of freezing HDPE pipes, on the contrary, they can give odds to any other type: even with surface laying in the lower limit of the temperature range, the plastic will retain its plasticity and will not allow ice to break the pipes.

In a filled state, HDPE pipes can be subject to significant mechanical stress. Their laying in an open way is allowed even at high throughput loads, but only without being hit by a vehicle. But laying in the ground can be performed even under highways, which will greatly simplify the supply of water to the site if the highway is laid on the opposite side of the roadway.

Range of fittings and valves for HDPE pipes

Along with high reliability, HDPE pipes have a developed and technological system of connections. Several types of installation systems are distinguished depending on the application..

HDPE compression fittings occupy a leading position in the market due to the absence of requirements for the qualifications of installers and the need for special equipment. But this is not a panacea at all: the press fitting must remain accessible for maintenance and replacement, therefore, their installation is allowed only when pipes are openly installed or in technical wells when laying underground. Note that press fittings are the only detachable connections for HDPE pipes..

Only HDPE fittings made in Israel and Italy have a service life comparable to the pipes themselves. If there are high requirements for reliability, it is better to pay attention to the connections with the drive sleeve. They do not require periodic constriction for the reason that initially they are pressed very strongly – the rigid insert does not allow the pipe to be deformed more than it should be.

For underground installation without the possibility of access, the method of machine welding is used. The electric welding unit tightly fixes the edges of the pipes, cuts them evenly and joins them after melting the edges. The method works for both direct docking and segment turns. Branching of the pipeline requires the inclusion of T-shaped elements of the factory casting.

The service life of such joints is equivalent to the pipes themselves, while the seam inherits all their strength characteristics, and the nominal passage does not narrow. This method of installation is associated with the involvement of “special installation”, but it is definitely cheaper than the device of technical wells with a long main line.

The third type of connection is the use of welded electrical fittings. Their fittings have terminals for supplying voltage to the spiral, which is hidden under a thin layer of plastic on the inside. Theoretically, such pipes can be soldered even with an ordinary battery without additional devices. And although in terms of viability such a connection is not inferior to the easel method, it is more susceptible to shock and static loads. For this reason, installation on electrical fittings is recommended only for stationary open-type pipelines, for example, when distributing water supply around the house and site.

Installation of main water supply systems

The abstract concept of a water main is a section of a pipe that has a large length with or without periodic insertion of branches. The advantage of polyethylene pipes for trunk systems is that they have a much longer length than most other types of pipes, since they are supplied in coils with a length of about 200 m.

In agriculture, where there is an urgent need to pump water over long distances, it is better to resort to trenchless laying. By means of small-scale mechanization, it is possible to lay the highway relatively shallow (40-60 cm), where it will not interfere with the passage of machinery and tillage. At the same time, the work is done really quickly: laying a hundred-meter span takes less than an hour.

Of course, in this case, damage to the pipes is not excluded as they are used. For example, if a sharp shard of stone falls under a pipe in an unstable area of ​​ground, this can lead to damage to the pipeline. By the way, such breakdowns are quickly detected due to shallow penetration and are easily eliminated. Nevertheless, if the operation of the plumbing system can in the future stretch for several decades, it is better to lay in a trench with bed preparation. In this regard, polyethylene pipes are very unpretentious: you just need to remove large solid fragments of soil and fill the pipe back.

Use in rough plumbing

HDPE also has a number of advantages in the distribution from the mains at the points of water intake. Compression mounting scheme provides sufficient reliability and high speed of work. The main prerequisite for using HDPE pipes for distributing water supply around the house and the site is high frost resistance and installation speed. Hand force is sufficient to tighten most of the cheap press fittings, while the openly laid system can be reassembled at any time..

The latter is very important in the use of HDPE pipes in temporary irrigation systems, when the location of the beds and the type of crops planted change from year to year. In drip irrigation systems, HDPE pipes are most widely used: for tapping taps under the tape, it is enough to drill a number of holes with a constant pitch, and the colored marker strip will not let you stray in the direction.

The range of applications is not limited to this. HDPE pipes are optimally suited for draining clarified water from septic tanks, and the 125 mm SDR 11 standard is an excellent means for free-flow transportation of wastewater over long distances.