What should be the size of sewer pipes

The efficiency of the sewer system depends not only on compliance with the technology, but also on the correct selection of sizes. It is the internal diameter that affects the main characteristic of any sewage system - throughput. An error in choosing a standard size can lead to the fact that the system simply cannot cope with the removal of drains.

How to choose the size

It is necessary to take into account the volume of effluent. For example, a sewage pipe 32 mm can be used when distributing sewage in an apartment (for example, to drain sewage from the sink). But the use of small sizes throughout the sewage system will lead to the fact that it will start working in pressure mode and the capacity will not be enough. That is, the water will stagnate.

You also need to consider the material from which the pipeline is made. For example, cast iron is used for risers and external sewage, but PVC and polyethylene pipes can be used both inside and outside the house. From the material depends mainly on the price.

Note! Steel pipe is practically not used for sewage. The sewage drainage system works in a pressure-free mode, so increased strength does not play a special role, but the susceptibility to corrosion cannot be counted as an advantage of steel.

The correct diameter should ensure that the cross-section is filled with drains approximately in the region of 0.5-0.6. For example, a sewage pipe of 40 mm will be suitable for the area from the sink, an increase in size will result in that some solid inclusions will not simply be washed off by the flow of water and will settle on the inner surface of the walls. The result of this can be problems with runoff.

Normative base

The dimensions and general requirements for pipes (in terms of geometry, quality control, etc.) depend on the material.

You can highlight such standards as:

• GOST 22689.2 - 89. It considers the sewer pipeline, made of polyethylene. Most of the standard is given to a detailed description of the sizes of shaped elements, the nominal diameters are also indicated. As for the length, according to GOST, the sections should be produced with a length of 2 to 8 m, it is allowed to change the length within arbitrary limits in accordance with the customer;
• GOST 6942-98. This document is about cast iron sewers. Despite the popularity of plastic, a cast-iron sewage pipe of 150 mm is actively used when laying the external system of drainage or as a sewer risers in the room. The standard does not mention the outer diameter, and the conditional passage Du;

• in the case of PVC pipelines, the situation is somewhat more complicated, because the regulatory document on free-flow sewage made of PVC pipes does not exist as such. But the requirements for such pipelines can be found in GOST R 51613-2000. It uses the concept of nominal outer diameter, so when selecting the size you need to take into account the wall thickness.

What sizes to choose for layout on the apartment

As a rule, the installation manual sewage misses the point of selection of sizes. Of course, in the ideal case, it would be necessary to calculate the exact amount of waste and, based on this, select D, but you can go another way. Most often, the averaged data on the diameters of the pipeline for wiring to the apartment, risers and the outer part of the sewage system are simply used.

The main rule when a sewage system is diluted in an apartment is that, in the course of the water movement, the diameter must either remain constant or grow.

When selecting sizes, you can use the following recommendations:

• if the apartment uses a combined drain for washing, sinks and showers, then a sewage pipe of 50 mm will do.;
• if the drain is separate, then the diameter can be slightly reduced, to about 32 mm;
• but in the toilet a small size is strictly prohibited to use. The diameter should be 100 mm.

Note! When distributing inside an apartment, it is necessary to take into account that in the area that dumps drains into the central riser, their volume is significant, so small size will not work.

Outdoor sewage

The external part of the sewage disposal system stands apart, water from the house is directed either to the internal drainage network or to the septic tank (in the case of an autonomous system). A sewage pipe of 100 mm is the minimum allowable size, for a small private house there will be enough capacity.

With the plastic pipeline problems, most likely, will not arise, but when choosing a cast iron product you need to pay attention to the labeling.

The most important parameters include:

• in fact, the diameter, if the marking is indicated as DN100, it means that Dвн is 100 mm, taking into account the wall thickness, the outer dimension will increase to 110;
• SMU marking means that both ends are smooth, but SME indicates that there is a socket at one end.

As for the cast iron pipeline sizes, the maximum inner diameter is limited to 400 mm (DN400), and the length depends on the type of connection. So, the pig-iron sewer pipe of 250 mm can be produced with a length of 3, 2.5 and 1 m, if the connection is socketed. But if the pipeline of increased strength will be laid (both ends are smooth), then the segment length is 3.0 m.

As for the riser, since the volume of drains in it is equal to the total volume of drains of the whole house, its diameter should not be less than 100 mm. In terms of material, it is possible to recommend both cast iron and plastic. A 75 mm sewer pipe is suitable for outlets from the riser.

Note! Cast iron pipe is not recommended for laying in the apartment with his own hands. This material is quite fragile and can crack even with a slight mechanical impact.

A general recommendation is not to use a size larger than DN150 for individual construction. Such a standard size with a reserve is enough even for a 2-storey mansion with several toilets and bathrooms. But the sewer pipe 200 mm is suitable for a hotel or a multi-storey residential building, but not for a family of several people.

Corrugated Pipeline

Plastic corrugated piping has a much greater ring stiffness than usual. Due to this, it can transfer heavy loads without consequences, that is, the maximum depth of the burial is increased.

For example, a 110 mm corrugated sewer pipe can be laid at a depth of up to 20 m. Such a pipeline is made of 2 layers of plastic, the outer layer is used to increase stiffness, and the inner one is smooth, which is necessary to minimize resistance to water flow.

As a rule, PE63 and PE80 polyethylene grades are used for production. This polyethylene is resistant to chemically aggressive substances, so that the composition of wastewater will not affect its durability.

In conclusion

Proper selection of the diameter of the sewer - the key to its success. To facilitate the selection problem, you can not perform the corresponding calculations, but use the averaged data. The information in this article will not make a mistake when choosing the size.

The video in this article shows an example of changing the layout of the sewage system in an apartment using pipes of different diameters.