How to connect polyethylene pipes for water supply

When organizing water supply, pipes made of various polymeric materials are very popular: polypropylene, metal, low pressure polyethylene, chlorinated polyvinyl chloride. Their gradual displacement of traditional cast iron and steel analogues is associated with their durability, low cost, strength and resistance to adverse environmental factors, ease and convenience of connection. Such advantages can significantly accelerate the installation of water supply networks, reduce their cost and complexity.

Methods for connecting water pipes

The method of connecting plastic pipes during the installation of the water supply depends on what material they are made of. The methods and tools used for pipelines from one type of plastic are not applicable to others.

Chlorinated Polyvinyl Chloride (CPVC)

Quickly and easily connect chlorinated PVC pipes as follows:

1. A piece of the required length is cut from the whole pipe using a special tool - a pipe cutter.
2. The workpiece is assembled with a fitting (angle, tee, sleeve) without gluing. In this case, the pipe distance that is included in the connection is measured.
3. With a special tool or a sharp knife, the bevel is removed from the end face of the workpiece.
4. The outer surface of the workpiece and the inner fitting are degreased using a special solvent.
5. A special layer of adhesive based on liquid chlorinated polyvinyl chloride is uniformly applied to fat-free surfaces with a thin layer.
6. The pipe is connected to the fitting at the required angle and fixed in this position motionless for 1 minute. Glue fastens the connected water supply elements very quickly and does not require additional efforts to fix them in the gluing process.
7. The remaining glue is removed with a sharp knife.

The plastic pipe assembled in this way works at high water pressure and does not leak. In case of unintentional damage to the water supply system, it can be quickly and simply repaired - for this, a suitable piece of polyvinyl chloride is inserted into the hole and poured with a thin layer of glue on top.

Pipes made of simple polyvinyl chloride (PVC) having a gray or bright orange color are not used in water supply networks. Their characteristics and the bell-shaped type of connection do not allow for tightness and stability of the water supply system - with high pressure they leak. Under the influence of hot water, they begin to collapse rapidly. Such communications are widely used for laying external and internal sewerage.

Metal plastic

The connection of metal-plastic water pipes is carried out using crimp and press fittings.

The crimp fitting is installed as follows:

1. Using scissors or a hacksaw, a piece of the required length is cut from the whole pipe.
2. The nut and compression fitting ring are put on the cut blank.
3. With a gauge or cone-shaped object, the inner diameter of the workpiece expands slightly - it is calibrated. When using the caliber, simultaneously with this, deburring occurs from the end face of the workpiece - countersink.
4. The fitting is inserted into the workpiece. For easier entry and to prevent scuffing and slipping of the sealing rubber rings, it is lubricated with liquid soap.
5. At the junction of the fitting and the workpiece, a crimp ring is thrust first, and then a nut.
6. Fix the fitting in the workpiece by clamping the nut with an adjustable wrench on the thread.

A metal-plastic water supply made using this technology, the riser of hot or cold water will last up to 10-12 years.In this case, the connection is collapsible, requires periodic inspection (1 time in 3-4 years) and tightening the nut if a leak is detected.

The connection process using press fittings is more time-consuming and requires special equipment - a manual or electric press. The sequence of fixing press fittings consists of the following manipulations:

1. The inner diameter of the pipe section is calibrated and countersinked using a special gauge.
2. A press fitting with a crimp sleeve is inserted inside the workpiece. The completeness of the contact of the pipe with the fitting can be judged with the help of special indicator windows on it - if they are completely closed by the pipe, then you can proceed to pressure testing. If not, it is necessary to repeatedly and more carefully calibrate and countersink the inner diameter of the workpiece.
3. Fix the fitting on the metal-plastic workpiece using an electric or manual press with nozzles of the appropriate diameter.

The crimp connection is more convenient compared to the crimping one - when a strong leak occurs that cannot be eliminated by tightening the nut, it can be disassembled, the o-rings replaced and quickly assembled. Although press fittings do not require periodic inspections and maintenance, they cannot be repaired if leaking or damaged.

Polypropylene

The most common method of connecting polypropylene pipes - high-temperature welding - consists of the following steps:

1. The necessary length is cut from the whole pipe.
2. The internal surface of the fitting and the external workpiece to be joined during soldering are degreased.
3. Using a black pencil that is clearly visible on a white background, a mark is made on the workpiece, indicating how much the pipe should go when soldering into the fitting.
4. The workpiece and polypropylene fitting are simultaneously inserted into the sleeve and mandrel heated to the required temperature on the tip of the soldering iron (apparatus for high-temperature welding of polypropylene products).
5. After 5-10 seconds, the soldered parts are removed from the working bodies of the soldering iron and are connected without rotation.
6. Until complete cooling, it is permissible to change the angle of the workpiece and fitting in a vertical or horizontal plane without rotating them relative to each other.

When soldering such pipes, it is important to observe the temperature and heating time of the parts to be joined. With prolonged exposure and high temperatures, polypropylene can melt strongly, blocking or narrowing the passage inside the water flow. Insufficient temperature and low shutter speed will lead to leaks due to incomplete fusion of the connecting surfaces of the fitting and the pipe to each other.

Plumbing products made of polypropylene will not connect well if there are water droplets on the surfaces to be soldered - moisture evaporating during soldering will interfere with the normal sintering of polypropylene and lead to the formation of cavities and holes in the solder joint.

Polyethylene

The connection of polyethylene pipes for water supply is carried out using compression fittings (couplings) as follows:

1. First, a crimping nut is put on the pipe, then a collet (crimping ring).
2. The pipe is inserted into the fitting body until it stops.
3. The collet moves to the threaded part of the fitting.
4. The fitting is fixed to the pipe by tightening the nut.

To connect HDPE pipes for large diameter water pipes (more than 100 mm), special welding machines are used that are used to install high-pressure water supply lines. To use such a device for mounting a household polyethylene water supply system of a private house is impractical.

Features of the connection of pipes from different materials

In practice, it is often necessary to connect pipes made of materials of different properties: metal and polypropylene, metal and polyethylene, polypropylene and metal plastic. Fixation Methods:

• To connect metal pipes with polypropylene pipes, combined couplings are used having male or female threads soldered into plastic.
• The connection of the pipe from polyethylene (HDPE) with steel is made using compression couplings. At the same time, the polyethylene pipe is fixed in the fitting in the traditional way, and the steel thread is screwed into the sleeve with pre-winding flax or tow and grease with a sealing paste. Large diameter polyethylene water flows will be connected to the gate valve, cast-iron tap with a special flange and strong bolts.
• Fixation of metal-plastic and polypropylene water flows is carried out using a solder sleeve and an apparatus for diffusion welding (a soldering iron for pipes made of polypropylene), or a crimp fitting and a transitional combined sleeve (polypropylene - internal metal thread).

Due to the simplicity and accessibility of methods for fixing polymer pipes, plastic water pipes, unlike metal ones, are mounted much easier and faster, without the use of threaded tools, physically heavy packages of threaded joints, and welding.