Sewage system in an apartment building: 6 main elements

Michel July 7, 2016Specialization: plumber with 10 years of experience, computer repair specialist, powerlifting coach. I have extensive experience in construction, interior decoration, and making homemade furniture. Hobbies: sports

Probably, few of the readers are familiar in detail with the sewerage system in an apartment building. In my article I am going to fill this gap by describing all the elements of the wastewater system, its typical problems and methods for eliminating them.

Scheme of the sewerage system in an apartment building.

Down up

Let's start with a simple listing of sewerage elements. When listing, we will move against the movement of stocks - from bottom to top:

1. The yard sewage well is located under the authority of the Gorvodokanal. It ends in a well that discharges the drains of several risers outside the walls of the house (usually from one entrance);
2. The outlet to the well is a pipe with a slope in its direction, laid through the foundation of the building and laid below the freezing level of the soil. The outlet discharges wastewater into a tray in the concrete bottom of the well;
3. Lezhnevka is a horizontal pipe connecting sewer risers;

Sewer bed.

I am using terms used in the region where I happened to work as a plumber. Often, even among professionals, the same object is called differently. The same bed can be called a sun lounger or simply a horizontal sewer.

1. A riser is a vertical pipe that collects drains from apartments located above each other;
2. Comb - intra-apartment sewerage. It got its name in those days when plastic wiring for apartments with adjacent bathtubs and kitchens was made monolithic and really looked like a rare comb for combing hair;
3. Fan pipe - ventilation outlet of the riser to the roof.

Now let's move on in the same order.

The principle of operation of home sewerage

Let's consider a simplified diagram of a typical sewer system in a standard apartment building.

The bathtub, toilet and sinks of a separate apartment are connected to a vertical riser using pipes. It receives drainage from apartments located one above the other in the same entrance. The risers of one or more entrances are connected to the house horizontal collector (it has a certain slope, calculated when designing the system), from which wastewater is moved into the yard sewer by gravity. Subsequently, through a system of pipes with control wells, the wastewater enters the central (external) city sewerage system.

Knowing how a typical sewer system works in a multi-story building, it is important to remember that the principle of its operation is based on the movement of wastewater by gravity .

Well

Description

If the storm sewer is closed with lattice covers to receive wastewater, then the yard sewer well is closed with a monolithic cover, which prevents the entry of foreign objects into it.

Well cover.

Its location is marked on the wall of the house with a designation of the form KK12, KK5, etc., in which the letters indicate the sewer well, and the number indicates the distance to this well in meters along a line drawn perpendicular to the wall with the designation.

A typical material for well walls is reinforced concrete rings with a diameter of 1000 mm. Steel brackets are fixed in the wall, allowing you to go down to the bottom level. The bottom is concreted to prevent untreated waste from entering the ground; There is usually a recess in the concrete - a tray that directs wastewater into the next well and then into the collector.

Problems

A blockage between the wells means that the entrance drains enter it, but do not go to the collector. Cleaning according to the current regulations must be carried out pneumatically:

Instructions for pneumatic clearing of blockages.

As you know, in our country not all technological operations are carried out in accordance with the regulations. Drain cleaning is no exception. In practice, sewer wire is used for it - steel wire with a diameter of 5 - 6 mm with a hook at one end and a handle at the other.

Cleaning is carried out as follows:

1. The coil of wire is completely unwound;
2. The mechanic goes down into the well and feeds the wire with a hook to the blockage;
3. His partner pulls the wire, preventing it from folding into loops, and rotates the handle, helping the hook break the cork.

Blocked yard drain.

This method has four serious disadvantages.

1. The walls of the well are always covered with a layer of dried sewage. A person who descends into it rises to the surface in a very unsightly form;
2. The brackets of old wells are often partially or completely destroyed: wet waste fumes have a detrimental effect on the steel;
3. Methane and other gases that are products of fermentation of wastewater or penetrating from the ground often accumulate in the well. By themselves they are not overly toxic; however, a lack of oxygen may well lead to loss of consciousness, and lifting an adult from a narrow shaft is more than a difficult task. The accumulation of gases in wells leads to the death of several people every year;
4. When clearing a blockage, a multi-meter column of sewage hits the opposite wall of the well with such speed and force that it is quite problematic to escape from the splashes.

Typical condition of a properly functioning well.

That is why experienced Vodokanal mechanics carry with them to accidents the simplest device - a pipe with a diameter of 32 - 40 mm, bent in the shape of a hockey stick. Its short side is inserted into the outlet from the side of the well, after which the wire is fed to the blockage through the pipe.

Outlet to the well

Description

The typical outlet diameter is 100-150 millimeters. The beginning of the outlet from the basement is equipped with a plugged tee for cleaning. The slope of the pipe is at least 1 centimeter per linear meter; changes in slope, and especially counter-slopes, are strictly prohibited, as they will inevitably lead to constant blockages.

Since the outlet is laid in the ground, quite stringent requirements are imposed on the strength of the pipes. The release is being laid:

• Cast iron pipe (including ductile iron pipe - high-strength cast iron with nodular graphite);
• An orange PVC pipe designed for outdoor use and with high ring rigidity.

Problems

With regard to the areas of responsibility in relation to the outlet, the situation is quite complicated: its blockages are cleared by employees of the housing department or the management company, repairs and replacements are carried out by them; however, damage to the outlet due to subsidence of the well walls must be repaired by Gorvodokanal. However, every controversial case serves as a cause for friction between interested parties.

Replacing the outlet with a well involves excavation work in the basement and outside.

The most common exhaust problem is a clog. Its causes are:

• Rags dropped by residents into the toilet when washing floors. The rag clings to any unevenness inside the pipes and quickly becomes overgrown with other debris;
• Fat plugs. Fat from the plates settles on the walls of the pipes as the wastewater cools, gradually reducing their useful cross-section.

In this case, sewer cleaning in an apartment building is also carried out using sewer wire. It is practiced to clear blockages from both the basement and the well.

Discharge to the well after cleaning from the basement side.

When clearing the grease plug, the hook at the end of the wire is made larger, and the wire itself, with continuous rotation, passes the blockage several times. The goal is to remove as much fat as possible from the pipe walls.

Installation errors and repairs

When installing ventilation ducts, inexperienced craftsmen make mistakes. They are usually associated with the desire to get the job done quickly.

The most common mistakes are:

1. The outlet of the fan channel is not on the roof, but in the attic. Over time, gases will accumulate in large volumes. Finding no way out into the atmosphere, they will begin to penetrate other rooms of the building.
2. Installation of the device on the outside of load-bearing walls. This will lead to condensation and subsequent troubles.
3. The use of decorative fungus on the upper part of the channel leads to a decrease in traction. As a result, the device does not perform its function. This leads to the spread of gases inside the building.

Repair of fan structures often involves replacing old cast iron channels with new polymer ones. It is advisable to perform this procedure under the guidance of an experienced specialist. Cast iron products are quite heavy. Moreover, they are characterized by a fragile structure. Careless handling will cause them to break. You need to be very careful when working with cast iron parts. Otherwise, you can cause damage to any elements of the structure and your own body.

If you need to replace ducts in a multi-story building on the ground floor, choose only high-quality replacement products. It is important that new polymer structures can withstand the existing pressure in the system.

To carry out repair work, you need various tools. You will need a drill, an angle grinder and a sledgehammer. To solve the problem, you may also need other tools. Since replacing cast iron products is a rather complex and time-consuming operation. After dismantling the old channels, install new ones. You already know how to do this.

Lezhnevka

Description

The lezhnevka unites the risers of the entrance and is laid with a constant slope towards the outlet to the well of 1 - 2 cm/m depending on the diameter. In houses built after the 70s of the last century, the typical diameter of the bed is 100 mm; in Stalinka and earlier buildings you can find beds with a diameter of 150 and even 200 mm.

The pipe is laid on supports (including basement bulkheads) or hung on steel hangers, which are anchored to the ceiling. The fastening pitch depends on the diameter and material of the pipe.

With a diameter of 110 mm, plastic sewerage is hung in increments of 1 meter.

With a large fastening step, the plastic pipe sags over time, forming counterslopes. Cast iron pipes are mounted as rigidly as possible on the sockets, which prevents the destruction of their seal.

The lezhnevka is equipped with revisions or (in the case of cast iron pipes) plugged tees for cleaning:

• On turns and bends;
• Every 8 meters on straight sections.

Problems

These include:

• Inevitable blockages. In addition to rags and grease, the list of causes includes construction debris, sand and cat litter that settle in areas with minimal slope;

A rag removed when cleaning the bench.

When plugs are installed and inspections are closed, blockage of the drainage pipe or outlet to the well leads to flooding of the apartments on the lower floor. The drainage from the entire entrance begins to flow into their toilets and bathtubs.

• Leaks at socket connections (including due to destruction of sockets).

How are these problems solved?

Eliminating a leak in a plastic socket comes down to re-joining the pipes, or less often, to replacing the o-ring seal.

A cast iron bell usually has to be re-coined. How to do this work yourself?

Restoring the tightness of a cast iron socket.

In addition to describing the algorithm of this work, it is worth mentioning a number of its subtleties:

• The easiest way to remove the old cement seal from the socket is with a chisel or a wide screwdriver. The cement is broken with a hammer and removed along the entire circumference of the pipe;
• The old heel can be removed with the same screwdriver;
• When re-minting, you can use a graphite gland instead of a heel: it is much more durable than organic fiber impregnated with oil or bitumen;
• For embossing, you can use either a specialized tool (a steel tube bent in the shape of the letter Z and flattened at the end) or a wide screwdriver;
• To seal the socket, you can use a cement-sand mixture in a 1:1 ratio or pure cement.

Chasing a cast iron sewer with sealing of the socket.

The blockage is cleared through the nearest tee or revision. It is advisable to clean it from top to bottom: otherwise, you may not have time to dodge the fetid stream rushing down the pipe.

Is it possible to somehow prevent flooding of first-floor apartments due to clogged drains?

Yes. It is necessary to leave the risers below the basement floor unsealed and at the same time to prevent sewage from entering the basement during normal sewer operation. This can be achieved in two ways:

1. By installing an oblique tee on the riser instead of an inspection;

If the riser is clogged, the drainage will flow through the tee outlet into the basement. Its flooding is also not a gift, but it’s still better than a flood in the apartment.

1. Replacing the inspection cover with a homemade one, equipped with a bend directed upward at an oblique angle.

Riser

Description

The typical diameter of a sewer riser is 100 mm. However, there are no rules without exceptions:

• In post-war houses I have seen risers with a diameter of 150 mm;
• In small-family houses of some layouts, kitchens are equipped with a separate riser with a diameter of 50 mm.

The riser is laid with socket pipes with the sockets oriented upward; At the floor level, tees and crosses are installed to connect the combs. Cleaning inspections include:

• In the basement, half a meter - a meter above the connection with the bed;
• On the extreme floors;
• In buildings of five floors and above - every three floors.

Inspection on a cast iron riser.

At the top, the riser extends beyond the roof and ends with a waste pipe communicating with the atmosphere.

Problems

There are four main problems with sewer risers.

Blockages

A clogged sewer in an apartment building in most cases is a consequence of violation of the rules for using the sewer. The riser is clogged by foreign objects that have gotten into it from apartments or from the roof.

The blockage is cleared from top to bottom through the nearest revision.

The inspection was opened to clean the riser.

For cleaning, we use the already familiar sewer wire. Strong and large objects that fall into the sewer require special measures: cleaning is carried out from the roof through the drain pipe and comes down to breaking through the blockage with a crowbar lowered on a rope.

Ventilation failure

In winter, the fan outlets of the risers often freeze: moist evaporation settling on the walls gradually reduces the clearance to zero. The thrust in the riser does not disappear anywhere; As a result, sewer aromas begin to saturate the apartments on the upper floors through leaky connections to plumbing fixtures and water seals damaged by the vacuum that occurs when toilets are flushed.

Evaporation frozen on the walls of the riser.

The problem is solved:

• defrosting the riser. For this purpose, it is enough to pour a bucket of hot water into the drain pipe;
• insulation of the drain pipe, preventing the freezing of vapors on its inner surface.

Noise

Plastic pipes have one unpleasant feature: they make the slightest noise in the riser audible. As a result, you hear the neighbors above draining water, the noise of the wind in the drain pipe, the sound of dripping from a faucet that is not fully closed, and other annoying noises.

The noise problem can be solved in two ways:

1. Installation of so-called silent pipes. They differ from conventional ones by the addition of mineral filler, increased thickness and variable density of layers;

Silent sewage system.

The price of a silent sewer pipe is 3 - 4 times higher than the cost of a regular PVC pipe.

1. Soundproof the riser with any roll insulation, foam shell, or a box made of plasterboard, wall panels or lining constructed around the riser.

Violation of tightness

Its typical cause is the destruction of the cast iron pipe socket or coupling under the weight of the pipe and due to corrosion.

The photo shows a destroyed cast iron coupling.

The defective area is replaced using a sewer coupling and a compensating pipe:

1. Two cuts are made above and below the destroyed bell. The distance between them should be equal to the length of the compensator;
2. The compensating pipe is pushed all the way onto the upper pipe;
3. A coupling is put on the down pipe;
4. The compensator settles into the coupling socket;
5. All connections are sealed.

To repair a cast iron riser, you can use a plastic fitting of the appropriate diameter. The surface of cast iron pipes is first cleaned of layers of paint and rust.

Requirements for a ventilated valve (aerator)

The installation of ventilated valves to allow air into the system (Figure 5), which guarantees normal operation of the sewer system, is carried out on the basis of appropriate calculations. The throughput of the aerator must correspond to the specified design parameters for the throughput of the riser. In turn, the fluid flow through the riser depends on its diameter, type (ventilated/non-ventilated) and height. The calculations also take into account the diameter of the dictating floor drain (with the highest waste flow), the angle of liquid entry through it, the height of the water seals and other initial data.

Figure 5. Operating principle of an aerator - air valve for sewerage: 1. In the operating position, the valve is closed - air from the sewerage does not enter the room. 2. When a vacuum occurs in the sewer riser, the aerator valve opens, the missing amount of air comes from the room, preventing the water seal from breaking.

In a simplified form, you can coordinate the flow parameters of the aerator and ventilated riser using tabular selections. Initially, you should refer to Appendix “B” of SP 40-107-2003 for the installation of internal sewerage from polypropylene pipes. It is to this that SP 30.13330.2012 refers to determine the characteristics of the aerator.

The largest valve with a live air flow cross-sectional area of ​​3170 mm2 ( Important! Look in the store not at the outer diameter, but at the size of its opening, roughly), if the design conditions are met, it is capable of compensating for decompression in risers ∅110 mm, the maximum throughput of which is indicated in table 1.

Table 1. Capacity of a riser made of polypropylene pipes ∅110 mm, equipped with a ventilation valve with a clear cross-sectional area of ​​the air flow of 3170 mm2 and 1650 mm2.

Next, you should find out the flow parameters of the sewerage system with similar initial data. For ventilated risers, they can be gleaned from tables 6-9 (SP 30.13330.2012).

Table 2. Capacity of ventilated risers made of polyvinyl chloride (PVC) pipes (SP 30.13330.2012 (Table 7)).

This also takes into account the diameter of the floor outlet and the angle of its connection. From the tables it becomes clear that, for example, for some of the most popular PVC pipes today, Ø 110 mm with an outlet Ø 110mm/450 (outlet for connecting a toilet), the second throughput of the riser will be 5.85 l/s. This figure turns out to be slightly higher than with similar geometric parameters of a sewer system with an air valve (5.44 l/s (Table 1)).

Consequently , by removing the decompression pipe and installing a similar aerator, during a salvo discharge it is possible that a vacuum may occur with dehydration of the siphons.

Comb

Description

A horizontal pipe collecting apartment wastewater from several plumbing fixtures is laid with a diameter of 50 mm. An exception is the toilet: the outlet for its connection should not have a smaller diameter than its outlet.

The toilet outlet is made of a pipe with a diameter of 110 mm.

The slope of a comb with a diameter of 50 mm should be 3.5 cm/m. To attach plastic pipes to the wall, clamps and clips are used; The attachment points should be no more than 40 - 50 cm apart from each other.

In the absence of clamps and clips, I laid the pipes on 6 mm thick wire driven into holes drilled in the wall. The ends of the improvised brackets were bent into a vertical position.

The connection of the comb outlets with plumbing fixtures is made airtight to avoid the appearance of odors. For sealing, standard sewerage seals or rubber cuffs are used.

The sealing cuff will eliminate the appearance of odors.

Problems

Plastic indoor sewage systems are characterized by only two problems:

• Smells. Their reason is in leaky connections of the comb with sinks and washbasins. To combat odors, it is enough to seal the joints with cuffs. As a temporary measure, they can be wrapped with regular tape;
• Blockages. A typical problem with a clogged 50mm comb is grease deposited on the walls of the pipe, which gets into the drain when washing dishes. The blockage can be cleared with a cable followed by rinsing with hot water; however, it is better to simply disassemble the sewer and shake out all the accumulated debris from the pipes.

Flared connections with O-ring seals can be easily disassembled for cleaning.

Cast iron combs of old houses often leak along the sockets. I described the method of minting cast iron sockets above.

Fan pipe

Its diameter in general should be equal to the diameter of the riser; however, in new houses it is common practice to combine two to four risers with one outlet pipe leading to the roof. I have already touched on the problems and their solutions in the “riser” section.

All you need to know about the sewer drain is that it is necessary for the normal functioning of the sewer system. The practice of replacing a drain pipe with a vacuum valve is not a complete solution. The draft arising in the riser in the absence of ventilation transports all odors to the nearest leaky connection on one of the upper floors.

Exiting the riser to the roof is not at all an extra detail of the interior.

Manufacturing materials

Plastic riser
Previously, most houses installed cast iron risers - heavy, expensive and prone to corrosion. They have been replaced by modern materials:

• Plumbing polymers. Products made from them are distinguished by ease of installation and low weight, the impossibility of corrosion and a budget price. The connections of the parts are sealed with special seals, which eliminates the need to use additional means, for example, silicone.
• Ceramics. It is not easy to install such products, but they are immune to corrosion and the formation of plaque on internal surfaces.
• Steel with anti-corrosion coating. Metal structures are usually installed in private homes. They are convenient and inexpensive, but over time they still rust.

Plastic models are considered the best option. If you choose the right angles of inclination in the horizontal sections of the structure, you can avoid deposits on the internal surfaces, as in more expensive ceramic products.

Prevention

I have written a lot about sewer problems, but not a word about how you can avoid them.

The rules and regulations for sewerage in an apartment building, which are mandatory for all residents, are simple and understandable.

• The toilet is used only for its intended purpose. Food waste, construction waste, thick paper, garbage are disposed of in other ways;
• The outlets of bathtubs, showers and sinks are equipped with grates or mesh to prevent foreign objects from entering the sewer system;

The mesh will protect the outlet from debris getting into it.

• Unauthorized transfer and change in the diameter of risers, benches and outlets to the well is strictly prohibited. If you want to change their configuration, contact your local housing organization for approval;

Changing the riser configuration requires approval from the management organization.

• Before you pour water into the toilet after washing the floors, take the time to make sure there is no rag in the bucket.

A simple recommendation will help you get rid of fatty plugs in the comb, which, alas, is often ignored by the rules for using sewerage in an apartment building published in the media. Wash dishes with hot water (literally on the verge of a comfortable temperature). I have long noticed that problems with fat deposits begin in the summer, when the hot water temperature drops to its minimum.