Water supply is the most important communication for providing household, drinking and industrial needs of a person, extinguishing fires. Water quality and operating parameters largely depend on the components of the system. Water pipes are the main element for transporting fluid in the network from the source to the consumer. There are many types of products on sale, differing in material, characteristics and price. Installation of each of them involves the use of certain technologies.
Types of water pipes and basic requirements
Water is supplied for various purposes:
- drinking, cooking;
- for watering;
- fire extinguishing;
- hot water supply;
- ensuring the production and technological cycle.
Pipes are used for external or internal water supply networks:
- steel straight-line seam according to GOST 10704;
- copper for water and gas GOST 52318;
- pressure pipes made of polyethylene according to GOST 18599;
- pressure pipes made of thermoplastics according to GOST 52134;
- multilayer from metal and polymers according to GOST 53630;
- asbestos-cement according to GOST 539–73;
- cast iron according to GOST 21053.
The standards normalize the inner and outer diameter of the pipe, wall thickness, mass per meter, strength, composition and properties of materials. Structures must be resistant to constant pressure, withstand the operating temperature of the medium. Damage, deformation, cracks or shells are not allowed on the inner and outer surfaces.
The external water supply is laid underground, the internal network is located in the building along or in the thickness of the walls, under the baseboards or under the floor.
The highest requirements for the quality of pipes for supplying drinking water to the house. Hazardous substances can enter the liquid and harm human health. So an excess of copper leads to liver cirrhosis, and an increased concentration of iron leads to the deposition of toxic compounds in human organs.
The main characteristics are outer (Dn), conditional or nominal (Dn or DN) diameters, wall thickness. Products with a diameter of 5–102 mm are classified as small, 103–427 — medium, over — large.
Water networks rely on a certain pressure indicator:
- up to 12 atmospheres — low pressure;
- 12–25 — medium;
- over 25 — high.
In apartments or private houses, pipes must withstand a pressure of at least 2 atm. The pressure in the internal fire water supply system is higher — up to 10 atm.
To transfer cold water, pipes with a temperature stability limit of up to + 46 ° are used. Transportation of a higher temperature medium is carried out by “hot” pipelines.
The question of which pipes are best used for plumbing can be answered by considering all the options and weighing the advantages or disadvantages of each.
Steel water pipes
Steel profiles are a traditional material for the manufacture of external and internal plumbing. They have mechanical strength and wear resistance, perceive multiple loads from pressure or temperature drops in the network.
Profiles are made of carbon steel by rolling (cold or hot), folding or welding. The sheet is cut into strips, aligned, welded in a straight or spiral line. Pipes are tested for strength under flattening and increased hydraulic pressure.
The need for steel pipes is great. More than 10% of all produced metal is spent on the production of these products.
Steel pipes are used:
- for laying water or gas pipelines;
- in industrial and civil construction;
- when laying highways;
- in the production of ships, aircraft, automobiles;
- in the metallurgical industry.
In housing and communal services, structures are used to organize systems for external and internal water supply, heating. For external laying, products with a cross section of up to 150 mm are used. When choosing the diameter of a pipe for a cold water supply in a private house, one should be guided by the length of the communication:
- up to 10 m — 20 mm;
- up to 30 m — 25 mm;
- more than 30 m — 32 mm.
The system is assembled by welding or using fittings. For threaded connections, a variety of components are produced.
The main disadvantage of steel communications is the instability to electrochemical corrosion.
The aggressive action of soil moisture or transported liquid gradually destroys the metal, leads to the formation of holes in the walls, through ulcers or pitting.
The standard service life of a water supply system — a riser or an eyeliner — made of steel pipes does not exceed 15 years. In fact, the action of destructive factors that shorten the duration of operation is possible. For example, cold water tends to corrode faster than hot water. The formation of condensate on the surface of the pipeline is accelerated due to the temperature difference, which leads to the destruction of the metal.
To avoid contact with water and oxygen, the effects of stray currents, the surface of the material is covered with a protective layer of zinc or polymers. Protective cathodic protection is used in outdoor networks.
Longer service life of galvanized profiles. This is due to the fact that the coating prevents the interaction of steel with moisture, and when water passes through, less deposits form on the inner smooth walls.
In the system itself, there is practically no scale or pieces of rust, leading to the formation of irregularities in the lumen. This increases the capacity of the galvanized water pipe, so for a home system it is enough to use bends with a diameter of 20 mm.
The standards determine the service life of a galvanized water pipe at 30 years. In reality, this period is higher — up to 50–70 years.
Galvanization is carried out in three ways:
- galvanic — applying a protective layer to the product, placed in the electrolyte, by electrolysis;
- hot galvanizing — the coating is fixed on the surface when the part is immersed in the metal melt;
- cold galvanizing — a protective composition is sprayed or applied by staining;
- diffuse — treatment with zinc vapor occurs at elevated pressure and temperature.
The highest quality protection is formed in the latter case.
Diameters of galvanized steel pipes according to the range of 6–150 mm (nominal bore). The outer section of the products is 10.2–165 mm. The length of the profiles is 4–12 m. The wall thickness varies from 1.8 to 5.5 mm. At the same time, the mass of coated structures exceeds black steel ones by 3%.
The assembly of the water supply system is carried out mainly by threaded connections with fittings. When using welding, the protective layer is damaged. Subsequently, corrosion centers form in these places. Thus, the meaning of the device of the galvanized system is lost, since the durability is reduced to that of simple black pipes.
To prevent damage to the coating during welding, zinc composition is sprayed onto the weld area, special fluxes or rutile-coated electrodes are used.
Pipes made of alloyed corrosion-resistant steel are durable, not subject to the destructive action of water. They can last up to 400 years. Oxidation products do not accumulate on the wall, do not enter the household water supply. Increasingly, stainless steel products are replacing conventional carbon steel despite the higher cost of the material and the complexity of installation.
Stainless steel structures comply with sanitary and hygienic standards, tolerate water hammer well, and are resistant to critical temperatures. Water with excessive chlorine content can damage stainless steel, so it is recommended to thoroughly rinse the system after disinfection.
Stainless pipes are used in various areas:
- water, heat and gas supply;
- arrangement of channels for air conditioning;
- laying “warm floor”;
- for protection of power electric cables.
The water supply is assembled using press fittings, also made of stainless steel, by welding with a tungsten electrode in an inert atmosphere. In industrial conditions, laser welding is used.
The device of a water supply system from flexible corrugated pipes is becoming more and more widespread. Their advantages are the possibility of laying in hard-to-reach places, installation of long lines, resistance to dynamic or vibration loads.
Copper plumbing is much more common in Europe than in our country. They are time-tested and deserve attention due to the long period of trouble-free operation.
Advantages of copper pipes:
- corrosion resistance — copper is insensitive to chlorine, dilute acids or alkalis;
- resistance to temperature drops within ‑100°С…+250°С, pressure fluctuations;
- growths do not form on the walls, bacteria do not settle, since copper ions are detrimental to them;
- with regular maintenance, the service life exceeds 50 years.
Copper pipes for plumbing in an apartment are subjected to additional processing — annealing. This gives softness and elasticity to products, they are easy to bend and cut. Such communications look very decorative. Additional painting with protective structures is not required.
The disadvantages include:
- higher price compared to steel analogues;
- for joining, only copper fittings can be used, since the metal forms a galvanic couple with steel, contributing to its destruction;
- the assembly of the system is carried out with special equipment, which increases the price of installation.
Pipes are connected by high-temperature soldering or using fittings, which must be combined. Cutting soft metal is not allowed.
The revolution in the chemical industry was marked by the emergence of new materials in construction. Various types of polymeric water pipes are made from thermoplastics or thermoplastics:
- polyethylene PE;
- polyvinyl chloride PVC;
- polypropylene PP;
- polyamide PA;
- polybutylene PB;
- epoxy or polyester.
The diameter of polyethylene pressure profiles is 16–1600 mm. The wall thickness is designed to withstand a working pressure of 4–20 bar. Products with a cross section of up to 40 mm are used for domestic plumbing, up to 160 — for risers or sewers. Larger ones are used in the field of production.
Polyethylene pipes are marked by density — from 63 to 100 (kg / m³). Less dense materials are mechanically unstable. Non-pressure structures are made from them — an outdoor shower, watering, sewer drains. PE 80 is stronger, they are used to install a cold pipeline inside the house. PE 100 is used to supply hot water and heating.
Polyethylene pipelines are mounted using compression or thermistor fittings, butt welding.
External water supply is laid from polyvinyl chloride pipes. They are gray in color and are available in lengths of 1, 2, 3 and 6 m. The nominal diameter of products is 90–500 mm. Designed for pressure 6–16 bar. Mount them without couplings or welding. At one end, a socket with an annular seal is formed, where the other part of the round profile is inserted. The connection is completely sealed, withstands standard loads.
Advantages of polymer pipes:
- resistance to chemical and electrical corrosion, exposure to aggressive environments;
- harmlessness, absence of harmful emissions into the transported liquid;
- smoothness of the inner surface, on which dirt does not linger;
- low thermal conductivity, reducing energy losses and condensation;
- light weight and plasticity, which simplifies transportation and installation;
- poor sound permeability, reducing the noise level during the passage of water.
During reconstruction, the system can be easily redone by cutting communications and connecting a new branch using a fitting. The construction of water pipelines made of polymer pipes is 30–40% cheaper than a similar one made of steel.
Disadvantages of products common to all plastics:
- instability to ultraviolet;
- high coefficient of linear thermal expansion;
- brittleness at low temperature;
- most of them do not burn, but support combustion, while emitting harmful substances;
- operating pressure and temperature limits.
The most heat-resistant pipes are made of cross-linked PEX polyethylene, which is produced under high pressure. Used for cold and hot water supply. Withstands temperatures up to +95° and pressure up to 20 atm.
Metal-plastic pipes are produced by extrusion, applying a melt of polymers to a frame made of mesh, wire or foil.
Metal-plastic materials combine the advantages of metal and polymer types of pipes for heating or plumbing:
- resistance to corrosion, chemical attack;
- small thermal expansion;
- wear resistance;
- simple installation using detachable, crimp or press fittings;
- operating temperature range up to 95°-110° and pressure up to 10 bar, withstand repeated freezing;
- service life up to 30 years.
Metal-plastic retains its shape when bent, does not emit harmful compounds into the water.
Disadvantages of water pipelines made of metal polymers:
- less mechanical strength than steel pipes;
- not applicable at pressures exceeding 10 bar and temperatures above 110°;
- some types are subject to fatigue failure.
The combination of positive qualities makes this material promising for wide application in various areas of construction.
To determine the most economical sections of the water supply, a hydraulic calculation is carried out. The condition for ensuring the required water flow, maintaining pressure and minimizing head loss must be met. Taken into account:
- estimated direction of water movement;
- consumption according to water consumption standards;
- characteristics of water fittings and the number of points;
- housing overcrowding rate;
- head loss due to friction along the entire length of the pipe.
According to the results of the calculation, the diameter of the water pipes is selected based on the size table and product range.
To determine the pressure loss, Shevelev tables or online programs are used.
The tables for the hydraulic calculation of steel, cast iron, asbestos-cement, plastic and glass water pipes contain ready-made indicators depending on the diameter, material, line length, network pressure. Losses are determined in each section and summarized. According to the found value, the required flow rate and pump power are determined.
The plumbing system is a complex engineering communication. It is important to choose pipes, taking into account their technical, to perform the installation correctly.