Insulation for sewer pipes: types, selection rules and overview of laying technology

Nikolay Fedorenko
Checked by a specialist: Nikolay Fedorenko
Author: Lydia Korzheva
Last update: August 2019

The operation of sewer pipelines is influenced by numerous factors, including cold. In order for the system to function normally even at very low temperatures, it is necessary to choose the right insulation for sewer pipes and install it.

Thermal insulation materials are presented on the market with a wide range, and it is sometimes difficult to decide on a purchase, agree? We will help you in solving this issue. The article provides an overview of various types of insulation, their characteristics, installation and application features are described.

Rules for choosing a heater

The construction market has a huge selection of insulation materials, but not everything can be used as insulation for sewer pipes.

The main task of insulation is not heating the outlet, but reducing heat transfer between the external environment and the fluid circulating through the pipes.

In order for the insulation for pipes to effectively perform its main function - heat conservation, it must meet 7 basic requirements:

  • have a thermal conductivity coefficient as low as possible;
  • keep their properties for a long time;
  • withstand large temperature differences;
  • have good waterproofing properties;
  • possess resistance to aggressive environmental influences;
  • do not sustain combustion and do not emit toxic smoke;
  • be easy to install.

Subject to insulation outdoor sewage pipes and a trunk laid in an unheated room. An exception is only those regions where even in winter it does not fall below 0 ° С.

For the rest, the only question is the choice of method and material. Heaters are selected based on the reputation of the manufacturer or brand, but the surest way is to focus on the material of manufacture.

Heaters for sewerage
In order to better navigate the variety of manufactured insulation materials, you need to proceed from 3 rules: if you find several materials that satisfy the requirements for them, choose the cheapest, easiest to install, long known on the market and well-established

Most often, sewer pipes are insulated with mineral wool, expanded clay, polystyrene and polyurethane foam insulation. Liquid heaters find their application. All of them are used for passive insulation.

In addition to them, there are 2 more options for protecting pipes from frost - laying below the freezing level of soil layers and the use of active heaters. The latter include cable insulation.

Mineral wool insulation

From the definition fixed by GOST 31913-2011, we can conclude that mineral wool should be assigned to the class of fibrous materials, in the production of which melts of rocks and metal slags were used.

The concept itself combines 3 types of material:

  • fiberglass;
  • slagged;
  • stone wool.

They have different thickness and length of the fiber, different indicators of thermal conductivity, moisture resistance, they react differently to mechanical loads, but the composition is identical in all. The characteristics of mineral wool produced by different manufacturers differ from each other.

The basis of mineral wool is rocks, there are about 90% of them in it. The rest is accounted for by additives - bentonite clay and resins with a phenol base.

Mineral wool meets the main needs - it has low heat conductivity, resistance to mold, fungi, fire. There are 4 options for this material: with fibers arranged horizontally, vertically, spatial view, corrugated

Mineral wool has a number of qualities that make you think before you make a choice in its favor.

The disadvantages of insulation include:

  • the presence in its composition of formaldehyde resins that adversely affect health;
  • the ability to shrink under the influence of mechanical loads and, as a result, the appearance of "cold bridges";
  • high water absorption, which is why the insulation needs good waterproofing.

Cotton insulation is used to equip open sections of sewer pipelines. They are not laid around pipes located in the ground.

When wet, this type of thermal insulation almost completely loses its qualities and often becomes the cause of rust on metal underground utilities.

Installation of thermal insulation from mineral wool is carried out in 3 stages:

  1. Foil tape is pasted onto the pipes in a spiral form.
  2. The pipe is tightly wrapped with insulation. In this case, the seams at the joints should match.
  3. Thermal insulation is mounted on the pipes by wrapping it with plumbing tape.

Given the fact that the density of the material is small, and it absorbs moisture well, waterproofing is required. To do this, use a foil or roofing material. The presence of a foil layer on the insulation makes the task easier, but the ends will still have to be insulated.

Glass wool pipe insulation

Glass wool, as one of the options for mineral wool, has all its positive and negative characteristics. It is a natural material derived from raw materials such as quartzite or sand.

The coefficient of thermal conductivity of this heat insulator is in the range of 0.028-0.034. The greater the thickness, the less it is. The average density is 150-200 kg / mᶾ.

Glass wool
The process of producing glass wool consists of melting the starting material with a temperature injection of up to 1400⁰. In this case, molten glass is blown with steam, resulting in thin filaments. They are impregnated with binding solutions, polymer aerosols, then they are fed to special rolls for leveling and forming, and after the material passes the stage of polymerization, cooling and cutting

To reduce hygroscopicity, some manufacturers produce glass wool with a finished insulation layer. It can be both foil and fiberglass. These include such popular heaters as Ursa, Knauf, Izover. The fiberglass heat insulator enters the construction market in the form of mats, rolls, cylinders.

Is it possible to insulate sewer pipes with slag?

The material is a by-product of cast iron smelting technology. Slag wool has a loose structure and one very unpleasant feature inherent in blast furnace products is residual acidity.

Under moisture conditions, acids are formed on the surface insulated with this material, which adversely affects both metal and plastic. Slag is melted at a temperature of 300 ° C, has a thermal conductivity of 0.46-0.48, and a fiber thickness ranging from 4 to 12 microns. It has low environmental friendliness

The coefficient of water absorption in this insulation for sewer pipes is higher than that of glass wool. The material is unstable to temperature differences, therefore, its service life is small.

For this reason, for the insulation of sewer pipes, it, like other cotton options, is rarely used, it is used only for insulation of overhead sections of communications.

The source material for its production of mineral wool are rocks. Basalt wool is a durable material with a density of 25-200 gk / mᶾ and a small coefficient of thermal conductivity - 0.03 - 0.04.

It is very resistant to temperature changes - it does not lose its original properties in the range of -60 + 200 ° С, but begins to melt when the temperature rises above 1000 ° С.

Stone wool
Basalt cotton wool is produced by many reputable manufacturers in various forms: rolls, mats, cylinders. The most famous companies are TechnoNicol, Rockwool, Knauff

Stone wool fibers have the same parameters as slag fibers, but they are much more elastic.Therefore, they do not break, do not enter the respiratory system, and do not irritate the skin. But there are also disadvantages to this type of mineral wool - high cost, insufficient strength and all the same phenolic substance in some grades of material.

Expanded polystyrene heat insulator for pipes

Foam shells are a popular insulator for warming sewer pipes. Two percent of its composition is small, from 1 to 5 mm, polystyrene granules, the remaining 98% is air. After processing the material with a blowing agent, the granules acquire lightness, elasticity, are attracted to each other and stick together.

By pressing, followed by steam treatment with high temperature, the material is given the desired shape.

In fact, it is a simple polystyrene, but in the form of a shell, designed for repeated use. The difference between the coefficient of thermal conductivity of polystyrene foam insulation (0.03-0.05) and mineral wool is small. The hemispherical shell copes with the task of preserving heat quite effectively.

The foam shell may consist of 2 or 3 elements. On their sides there are locks with a device for securing. The shell is selected according to the diameter of the pipe and, having put on it, snap

Since the foam is not very resistant to mechanical stress, manufacturers supply the shells with an external coating of aluminum foil, fiberglass and other materials.

High heat-insulating properties provide thin-walled microcells that do not allow heat to pass through. The service life of the insulating shell is quite large - about 50 years.

There are 2 types of this material - ordinary and extruded polystyrene foam. The characteristics of the latter are higher, but the cost is different upwards.

Despite the mass of positive qualities, polystyrene foam also has disadvantages. It does not tolerate ultraviolet radiation, therefore, when laying pipes in open places, additional protection from the sun is required. This material is dense but brittle, and when burned it can cause poisoning, as the smoke emitted by it is poisonous.

Installation works are so simple that they do not require special qualifications. Having put the insulation segments on the sewer pipe, they overlap, moving them 200-300 mm in length relative to each other. In order to avoid the appearance of cold bridges, thermal insulation elements are joined together using a quarter system or spike groove.

After the connection is made, both parts are strongly compressed. Contact points are glued with tape. Sometimes the joints are coated with glue, but then the insulation loses such an advantage as the possibility of reuse, because when dismantling it will have to be cut.

A protective coating is put on the shell, which comes complete with it or simply wrapped with a plastic film, if it is not.

Use shells both on elevated routes, and for underground laying. This insulation can be put on a pipe with a minimum diameter of 1.7 cm and a maximum of 122 cm. Already with a diameter of 200 mm, the cylinder consists of 4 elements, and for large products there may be 8.

Trenches with sewer pipes are first covered with sand to a height of about 0.2 m, then with earth. In regions with very cold winters, thermal insulation in the form of expanded polystyrene shells is supplemented with an insulating cable, placing it under the shell.

Polyurethane Shells

Polyurethane foam cylinders are a good alternative to foam analogues. They differ in comparison with them in higher density, and the coefficient of thermal conductivity is almost the same.

Higher polyurethane foam and resistance to mechanical stress. It also has a wider temperature range in which it can be operated without loss of strength characteristics.

Polyurethane foam
The normal temperature for a polyurethane shell is -180⁰ - + 130⁰. This material has a high fire safety rating - it lights up at 415⁰ and then self-extinguishes

Thermal insulation has the form of half-cylinders equipped with transverse or longitudinal latches. To increase the reliability of protection, shells are sometimes enclosed in special galvanized casings equipped with locks, but more often they simply apply special coating.

The use of foamed polyethylene

As a heater of sewer pipes, foamed polyethylene is often used. This is not a very dense material - up to 40 kg / mᶾ. The coefficient of thermal conductivity is in the range of 0.05.

It does not change its properties during operation in the temperature range of -50 ° С - + 90 ° С. The small thickness of the material allows you to save space, so its use is justified where there is a very small gap between the pipes and the wall.

Polyethylene foam
Foamed polyethylene well tolerates even prolonged exposure to moisture. It is fireproof. Withstands over 300⁰. When a material burns, its emissions into the atmosphere do not contain hazardous toxins.

The advantage of insulation is lightness, durability, affordable price. Manufacture such insulation as manufacturers Magniflex and Penofol, Energoflex, Thermoflex. They release it in the form of cylinders of different diameters and in rolls. There are foil one and 2-sided options.

This option of thermal insulation in the arrangement of sewer pipes is rarely used, it is used to warm the sections of communications located in the basement and above the ground.

The use of foil isol for pipe insulation

Most often, the material is used for outdoor communications made of plastic pipes. There are 2 varieties of foiloisol - SRF and FG. In its production, foil is used - corrugated or aluminum and bitumen-polymer layer for bonding.

On sale comes in the form of rolls. The material is durable, environmentally friendly, has a long shelf life. Well established in regions with different climates.

Foamed rubber as insulation

This insulation material is made on the basis of natural or combination rubber. It is characterized by high fire safety, elasticity. Pipe insulation using this material is done by gluing. As a result of the interpenetration of surfaces, a durable seam is obtained.

Foam rubber
The structure of foamed rubber is closed, porous. Because of this, it has increased flexibility. In the construction market, this thermal insulation is presented in the form of sheets, cylinders, rolls

Thermal insulation is produced by manufacturers such as the Italian company K-FLEX, German companies ARMAFLEX and KAIFLEKS. Due to the high cost for the insulation of sewer pipes, foamed rubber is used extremely rarely.

Expanded water insulation with expanded clay

The material is used for thermal insulation of sewer pipes laid underground. Its normal functioning is possible only in a dry environment, therefore, the work of warming is performed in warm, dry weather.

The technology is simple:

  1. Under the pipe, 2 layers of the membrane with a cloth overlay on the walls of the trench are placed.
  2. Expanded clay fall asleep.
  3. Lap the edges of the panels on top of expanded clay.

In the event of moisture, this bulk material loses its properties. It is advisable to use in areas with a temperate climate, as It is not very effective in the role of insulation.

Expanded clay - a heater of sewer pipes
Since clay is the basis of this material, it has retained all its characteristics. Expanded clay has a chemical inertness, does not support decay processes, but is unstable against sharp shocks and absorbs moisture well

The density of the material depends on its brand. There are several types of expanded clay with different densities, shapes and sizes of granules. High-quality expanded clay has the correct rounded shape and uniform internal structure.

Heat-insulating paint as a heater

Visually heat-insulating paint resembles ordinary. Its advantage is that it can be applied to the surface of any shape. The paint layer forms a tight elastic coating, working on the principle of a thermos.

The coating with high energy-saving characteristics is a multi-level system, which includes vacuum microspheres of various types, an acrylic binder, modifying additives that resist the appearance of rust on the surface of metal pipes and mold

For the production of microspheres, ceramics, perlite, foamglass and other substances with thermal insulation properties are used. The paint is very convenient to use and creates a coating that is durable.

The effect of coating with such paint is the same as that of insulation with mineral wool or polystyrene foam. Apply it both manually with a roller or brush, and with a spray.

When is an insulation cable needed?

If sewer pipes, due to the impossibility of deepening them, are laid on the surface of the earth, then the most effective way of insulation for them will be a combination of several materials plus electrical cable.

The following selection of photos will introduce the process of installing a heating cable:

The same method of insulation is advisable in the case when the pipes are at a depth less than the level of freezing of the soil.

The reason for laying sewer pipes without being buried in the ground can be a high level of groundwater, soil with a rocky structure, permafrost

There are 2 types of products: resistive and self-regulating. In addition to the first, temperature controllers are required. It can be either single or 2-core. The most practical option is self-regulating cablehaving effective protection against overheating and good thermal conductivity.

Its resistance decreases with decreasing temperature and increases with its increase. The third type of cable - zonal is used when it is necessary to bring heat only to individual sections.

Conclusions and useful video on the topic

The author answers the question of the advisability of warming pipes located below the freezing level:

Advantages of using heat-insulating cylinders made of extruded polystyrene foam:

The trouble-free service of the sewer system largely depends on the quality of the pipe insulation. Of all existing methods of thermal insulation of sewer pipes, one should choose one that corresponds to climatic conditions, the depth of pipe laying, and the characteristics of the highway.

Do you have practical skills in warming sewer pipes? Share your knowledge, ask questions about the topic of the article and participate in discussions. The communication unit is located below.

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Visitors Comments
  1. It seems to me that the appearance of the bulk of the materials is more like a marketing move. He lived in Kolyma and there we insulated both sewer and water pipes with plain glass wool. Moreover, the pipes were previously laid in concrete or wooden boxes. In principle, such an option is quite sufficient both in terms of performance and durability.

    • Denis

      I do not agree. I myself used glass wool for a long time, I can say with confidence that it is destroyed under the influence of high humidity and temperature extremes. At the new cottage, he insulated the pipes with a foam shell. This is also cheap, but much more durable material. To ensure water protection, according to the master involved in the work, an external foil sheath of the material is sufficient, which simplifies the installation process. If there is no casing, then ordinary aluminum foil will do.