A sewage system mounted in accordance with SNiP with observance of slopes, depth below the freezing zone and installation rules will work flawlessly. But it is not always possible to follow the prescribed instructions, so the pipelines are insulated with the help of special materials. They allow you to reduce heat transfer between the contaminated environment and the soil, thereby preventing freezing.
When sewer pipes need insulation
If the outdoor air temperature drops below 0 degrees, the drainage system must be insulated even in unheated rooms. The question is in choosing the right materials. At the same time pay attention to the brand name of the manufacturer.
To avoid additional costs for pipe insulation, they are laid below the level of soil freezing, information can be found in the directories. In the permafrost zone and in the northern regions, it is necessary to apply active insulation using heating cables that wrap the pipeline.
Sewer pipes in a private house can not be insulated due to the following factors:
- The drainage system is based on the principle of gravity flow, drains do not fill the entire internal volume and do not stand in them, as happens in water pipes. Due to the slope, all drains after the work of plumbing fixtures enter the septic tank without stagnating inside the pipeline.
- The minimum temperature of tap water is 3-5 degrees. For the formation of the crystalline structure of ice, static water molecules or abnormal weather conditions are necessary.
- When wastewater is discharged to an aeration station, the cleaning process occurs with the release of heat. Through the condensation pipe is the removal of warm gases in the direction of the fan riser located in the house.
However, all of the above is offset by improper installation in violation of SNiP. The system freezes if the pipe has stagnation zones where ice is formed as a result of not observing the required slope, or the pipeline was laid without a sand cushion and sprinkling. As a result, due to the expansion of the freezing soil, the pipe “walks” with the formation of the same stagnation zones or sags as a result of improperly compacting sand.
Types of thermal insulation for sewer pipes
Most often, the following materials act as a passive insulation:
- mineral wool;
- glass wool;
- slagged;
- expanded clay;
- polystyrene foam or polystyrene;
- polyurethane foam;
- foamed polyethylene.
Mineral or stone wool is a fibrous material that is obtained by heating rocks to a melting point of 1500 degrees. The resulting mass, reminiscent of lava, goes to a centrifuge, where stone threads are drawn using air flows and filters.
Fiberglass is obtained from quartz, sand or recycled materials. Broken glass is melted and passed through microscopic holes. The resulting glass filaments are wound on coils, then treated with a sizing agent, as a result of which the material becomes waterproof and resistant to abrasion. Glass wool has good thermal insulation properties, flexibility and strength. With increasing fiber thickness, heat loss decreases.
Slag is obtained from liquid blast furnace slags, which are blown using steam or air flows. All of the listed fibrous heaters have different thicknesses of threads, thermal insulation properties and moisture resistance.The material belongs to non-combustible compounds, at a temperature of 250-300 degrees it loses its insulating properties, and the formaldehydes contained in it reduce the area of its application.
The foam insulation consists of polystyrene granules (2%) and air (98%). The particle size is 1-5 mm. Using a blowing agent, the elements are glued together, then under the press they form a shell that can be used repeatedly. Thermal conductivity is almost the same as mineral wool.
Polyurethane foam has a density and strength higher than that of polystyrene with the same thermal conductivity. The material is better preserved during operation and can withstand temperatures from -180 to +130 degrees.
Foamed polyethylene or energy flex has a low thermal conductivity of 0.05 and takes up little space, therefore it is used in small gaps between the pipeline and the wall. The insulation works in the range from -50 to +90 degrees. They are produced in the form of cylinders and rolls, as well as one or two-sided foil products. Most often used in basements and unheated structures for internal sewage and floor insulation.
Expanded clay is a bulk material that retains heat-insulating properties only in the dry state.
Penoplex or extruded polystyrene foam is available in the form of segments of different thicknesses and has a low cost.
Selection recommendations
There are several criteria that the selected insulation materials for the external sewage pipeline must meet:
- low coefficient of thermal conductivity;
- providing reliable waterproofing;
- durability;
- resistance to temperature changes and aggressive chemical compounds;
- easy installation;
- high fire fighting properties.
If the heaters meet these conditions, stop at the cheapest option.
Insulation Installation
Each type of material has its own installation method.
Installation technology of fibrous insulation:
- Wrap the sewer pipes in a spiral pattern with aluminum foil tape, aligning the joints so that there are no missing sections. This material has good heat and moisture insulation properties.
- Thermal insulation material is fixed with plumbing tape.
- For waterproofing, roofing material or adhesive tape based on aluminum foil is used.
Butt ends need additional protection against moisture penetration.
Polystyrene insulation mounting technology:
- Shells in the form of segments are wrapped around the pipes so that the grooves coincide, along the length they are displaced by 20 or 30 cm (overlapping) so as not to miss uninsulated sections. No special qualifications are required for the performance of the work.
- The shells are squeezed and the joints are sealed with tape. It is not recommended to apply glue, since the possibility of reuse after repair is lost.
Polystyrene insulation is used with pipe diameters from 17 mm to 1200 mm. For pipes with a large cross section, up to 8 insulation segments are used.
Expanded clay laying technology:
- line the trench with two layers of the membrane;
- pour expanded clay;
- overlap thermal insulation material with overlapping panels to isolate from water.
This type of insulation can only be installed in dry weather.
Cost of insulation
Expanded polystyrene 50 mm thick is supplied for pipes with different diameters, so the cost of products varies. The price of a heat-insulating shell for sewer pipes with a diameter of 110 mm is 175 rub./m.po; D57 * 50 for 125 rubles / mp; D160 * 50 for 230 rubles / mp
The durability of expanded polystyrene is 40 years. The material does not require additional insulation coating.
Mineral wool half-cylinders with a length of 1000 mm and a thickness of 20 mm have different costs depending on the diameter: from 40 to 266 rubles / mp; with a thickness of 30 mm - from 81 to 611 rubles / mp; with a thickness of 40 mm - from 109 to 705 rubles / mp
Packing of pipes from polyethylene 30 m.p. with a diameter of 110/9 mm with a product length of 2 m costs 110 rubles.
