The high level of groundwater is a hydrogeological situation that adversely affects the technical condition of underground structures. Contacting with concrete or brick structures, water gradually but extremely persistently destroys them.
To reduce the GWL and drain water is designed drainage system. One of its functional parts are drainage manholes, necessary for the inspection and cleaning of underground utilities.
Before proceeding with the installation, you should determine the optimum type of well, prepare the necessary materials and familiarize yourself with the installation instructions. All these questions are studied in detail by us, and the answers are set out in this article.
The content of the article:
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Types of drainage manholes
- Designs for gravity nets
- Inspection wells for pressure networks
- Types of drainage manholes
- What material to prefer
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How to mount a viewing well
- Development of the pit and its size
- Device of the basis of a drainage well
- Installation or production of the bottom
- Production of a receiving tray for pipes
- Installation of the first ring of the working chamber
- Installation of overlap and neck
- Performance of a waterproofing of the working camera
- Finishing work: backfilling and installation of the hatch
- Conclusions and useful video on the topic
Types of drainage manholes
The drainage manhole is a hydraulic underground structure designed to monitor and periodically clean the system.
The shape of the well in the plan can be rectangular or round. Used for pressure and free-flow drainage system, but with some differences.
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Inspection wells are arranged on the branches of all types of sewer systems. The distance between adjacent wells depends on the terrain, the complexity of the route and the diameter of the pipe
The length of the pipe between the wells reaches 300 m for collector pipes with a diameter of 2 m. For small systems the distance is calculated from 25 m, is selected so that cleaning through the well can be done in both parties
Mandatory mine manhole with bottom tray installed on the bends of the system. The bottom of the shaft is equipped with a tray with a smooth rotary recess.
Nodal manholes are constructed at the confluence of two or three branches with the exit of one pipe. In large collectors they are called connecting chambers.
The control variety of manholes is arranged in the place of interconnection of the intra-block or yard system to the centralized network.
For stormwater and drainage sewage, a single collector well can be installed, which receives drains from both systems and transfers them to the disposal site.
In areas requiring slower transportation of wastewater, drop points are set at points of elevation elevation and location of underground utilities.
At the starting sites of the sewer network, where, due to the low speed of the movement of drains, sedimentation is possible, wash wells are built
Linear version of the manhole
Pipe length between points
Turntable manholes
Nodal sewer
Bottom of control manhole
Manifold option sewer well
Drop type manhole
Wash well
Usually, arrangement of drainage circuits make a free-flow scheme. This is a network of interconnected drainage collectors, along which the floodwater and infiltrated groundwater collected by drains flow by gravity. The force of gravity stimulates the movement of flows to the collection and disposal sites.
The pressure system is characterized by the forced movement of wastewater, the transportation of which is carried out through the operation of pumping equipment.
The pressure system is arranged where their spontaneous movement to the drives for removal and disposal or to the treatment plant for processing is impossible. For example, if it is not possible to install the drive below the level of the gasket drains.
Both types of sewer systems are constructed according to SNiP 2.0403-85 “Sewerage. External networks and facilities.
The construction of the drainage well for free-flow or gravity system. The neck and the working chamber are equipped with a ladder (+)
Designs for gravity nets
At the device of free-flow system count drain pitch. I put the trunk in a straight line connecting the branches with wells.
It is necessary to provide inspection drainage wells on the following plots:
- direct drainage piping for inspection and maintenance;
- connection and branching of the drainage pipeline;
- changes in the diameter of the drainage pipe;
- changes in the slope of the drainage pipe;
- changes in the direction of flow (rotary well).
For straight sections of the drainage pipeline, the maximum length is set at which a manhole device is required.
This value depends on the diameter of the pipeline:
- 35 m - Ø 150 mm or less;
- 50 m - from Ø 200 to 450 mm;
- 75 m - Ø 500 to 600 mm;
- 100 m - Ø 700 to 900 mm;
- 150 m - from Ø 1000 to 1400 mm;
- 200 m - from Ø 1500 to 2000 mm;
- 250-300 m - over Ø2000 mm.
Such a dependence of the length of the pipeline on the diameter is given in the regulatory documentation governing the rules for the construction of all types of sewer systems. It is based on long-term practice of construction, control and maintenance.
The size of the manholes (working chamber in the plan) also depends on the largest diameter D of the drainage pipe.
Values for rectangular wells:
- up to Ø 600 mm - 1000 mm for length and width;
- Ø 700 mm and more- D + 400 mm for length and D + 500 mm for width.
Most manholes have a round-shaped working chamber.
The dependence of the diameter of the well Ø from the diameter of the pipe D:
- Ø 1000 mm - up to D 600 mm;
- Ø 1250 mm - D 700 mm;
- Ø 1500 mm - from D 800 mm to 1000 mm;
- Ø 2000 mm - D 1200 mm.
The dimensions of the rotary well can be increased to ensure the minimum turning radius of the trays.
There are several reservations on the size of the manhole associated with the depth of the bottom of the structure:
- if the depth of the manhole is 1.2 m and less, a 700 mm diameter well is allowed for pipelines not exceeding 150 mm;
- for wells with a depth of 3 m and more, the minimum size of the working chamber is at least 1500 mm.
Shallow inspection wells, which maintenance and inspection can be made from a surface, are called inspection. Well structures that require the performer to dive to a depth of more than 1 m are classified as serviced.
The manhole of the drainage system, the bottom of which is laid at a depth of up to 1.2 m, is intended to provide inspection and maintenance from the surface
The height of the working chamber of the manhole is measured from the bottom (base plate) to the upper face of the neck. It depends on the depth of the drainage system and its purpose: the removal of groundwater from the foundation or the drainage of a private site.
The neck of the well provides access for the person and the equipment to the inside of the working chamber, the most suitable diameter for this is 700 mm. For descent into the working chamber, the manhole is equipped with brackets or a ladder.
When arranging trays for drainage pipes, the height of the shelf shelf is determined by the largest pipe diameter. The upper lines of the tray shelves should be flush with the top of the pipe.
The design and dimensions of the manhole for the drainage system should provide access to the pipelines for maintenance
Inspection wells for pressure networks
Pressure piping does not need to comply with slopes. In addition to standard functions, pressure manholes form rational places for installation, adjustment and maintenance of equipment.
Arrange them in places of installation:
- locking equipment;
- pumping stations;
- in places of accession to highways.
The size of the working chamber depends on the mounted equipment. Depth should be 0.5 m deeper than zero temperature penetration. If this is not possible, the wellbore should be warmed to the specified depth.
The distance from the walls of the working chamber to the pipeline must be at least:
- 0.3 m for pipes Ø 400 mm and less;
- 0.5 m for pipes from Ø 500 to 600 mm;
- 0.7 m for pipes Ø 700 mm and more.
The height of the working chamber should be at least 1.5 m. For the descent, the well is equipped with iron brackets or a ladder.
Inspection wells for drainage pressure networks are arranged at the points of connection of valves, pumps, connecting adjacent branches and in places of discharge of wastewater into storm sewer
Types of drainage manholes
Inspection wells designed for free-flow drainage system are divided into the following types:
- linear;
- rotary;
- node with one or two nodes of accession.
Standard constructions of prefabricated concrete inspection wells developed according to series 3.003.1-1 / 87 “Prefabricated reinforced concrete whole-shaped wells for underground pipelines”.
Structurally, manholes of all types of sewer systems differ in the number of inlets / outlets and their location
Linear wells arrange on straight sections of the pipeline, have two pipes: supply and discharge.
Pivot wells characterized by the allowable angle of rotation of the pipeline, which depends on the diameter of the pipe and the size of the working chamber.
Nodal wells built in such a way that the connected pipelines had an acute angle with the main pipeline in the direction of the fluid.
The diagram shows the plans of manholes with working chambers 1000, 1200, 1500 mm (+)
What material to prefer
Inspection wells can be industrial or self-made. As a rule, the project of a well is coordinated with the operating organization.
The industry offers various options for ready-made inspection manholes made of: concrete, polymers or composites. Wells of self-production can additionally be made of brick, rubble. Each material has its pros and cons.
In the manufacture of drainage wells with their own hands, it is necessary to consider the frost resistance and moisture resistance of materials
The vast majority of drainage wells are made of reinforced concrete rings.
The use of concrete has its advantages:
- excellent resistance to buoyancy of water;
- the ability to hold large loads;
- the ability to manufacture by hand on site facilities;
- low price
Reinforced concrete has a density of about 2.5 times more than water. It has a large mass and high coefficient of friction with the surrounding soil, which well compensates for the buoyancy force of water.
However, a large mass of concrete has its disadvantages:
- the need to use lifting equipment;
- the complexity of the holes for the input and output of drainage pipes;
- the need to arrange access roads for the period of installation works;
- the inability to achieve full waterproof.
Composite and polymer manholes factory readiness can be used on pipelines up to 400 mm.
The construction of a plastic manhole resembles a designer, the shaped and functional parts are well suited to each other. Plastic is easily sawn to achieve the required dimensions.
Modern urban planning is increasingly using polymer drainage wells.
There are several reasons for this:
- ease of installation;
- a wide range of fittings;
- high speed of construction;
- tightness;
- low weight
Transportation of polymer or composite wells is carried out by ordinary freight transport. For the assembly and installation of the well enough for three people.
However, such wells also have disadvantages:
- high price;
- insufficient resilience;
- Production on individual project data is very expensive.
When purchasing a plastic well, it is necessary to pay attention to withstand loads, especially if the well is mounted within the roadway.
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Step 1: The assembly of the plastic well begins with the installation of the bottom on the tamped bottom of the trench or pit
Step 2: For the device of the mine from the corrugated plastic pipe, the piece specified by the project is cut off
Step 3: The sealing ring is installed on the extreme recess of the corrugations, then the edge with the seal is connected to the bottom
After connecting the pipes to the manhole, the trench or excavation is filled in layers with soil. At the end of the shaft is installed on the mouth of the hatch
Installation of the bottom of a plastic well
Cutting plastic pipe on the elements
Seal for bottom connection
Dumping the soil in a trench or pit
Brick wells have pros and cons similar to concrete wells. An additional advantage of a brick well can be attributed to the simplicity of achieving the specified size. However, such a well requires more time for construction.
It is convenient to use a brick to obtain the required dimensions, since the necessary concrete products are not always available.
How to mount a viewing well
By the time of the start of work on the installation of a drainage well, the pipeline must be laid, but not filled.
The general progress of construction work:
- digging of the pit;
- base device;
- installation or production of the bottom;
- manufacture or installation of the tray;
- installation of the working chamber of the well;
- mounting the top of the working chamber and the neck;
- waterproofing of the working chamber;
- backfilling and installation of the hatch.
Consider the option of building a readiness well. With self-construction construction stages are similar.
Development of the pit and its size
Before starting the development of the pit, make sure that there is no ground water at the bottom of the well. If there is water, then it is necessary to build a temporary drainage pit or carry out periodic pumping.
The pit is produced according to the size of the planned well to the device. The bottom of the pit should be larger than the base of the future structure. The less dense the soil and the less clay particles it contains, the less its ability to “keep” the shape of the mine.
During the development of a pit in loose, easily crumbling sandy soils, the work on dumping is usually much greater than in the development of a pit in sandy loams and loams. If the shedding of waste rock will interfere with the development of the excavation, the walls of the excavation will need to be strengthened.
The depth of the pit perform more at 35-40 cm lower level of the drainage pipe. Mark the pipes checked level.
When the depth of the pit is greater than the height of a person, there is the likelihood of an accident when the soil collapses. It is necessary to install gentle slopes and wall reinforcement.
Device of the basis of a drainage well
After the excavation has been dug, coarse gravel or crushed stone of a 10-20 mm fraction is poured at the bottom. A thickness of 20 cm is sufficient.
If at the bottom of the excavation the soil is dry and dense, you can make the filling until the irregularities are eliminated, the main thing is not to allow play or skewed bottom
On top of the coarse rocks fall asleep sand with a layer of 10-15 cm. Then it is plentifully moistened and carefully tamped. A good level of density of the base can be considered a seal in which a person's foot does not sink into the sand (shoes do not leave fingerprints).
Installation or production of the bottom
The construction of the bottom is a crucial stage of the entire construction of the manhole, since it is the bottom that takes the entire weight of the structure and determines its verticality.
There are two options: make it on site by hand or mount it ready.
Option one. It is necessary to ensure the absence of water for at least 2 days, otherwise a large part of the binder will be washed out of the concrete. The bottom thickness should be at least 10-15 cm.
For the reinforcement of the bottom using rods with a diameter of 6 mm. A grid with a mesh size of about 10 cm is made of reinforcement.
First pour half the volume of concrete. After setting of the bottom part, the grid is laid and the concrete is poured to the required thickness of the well base. The ends of the reinforcement around the perimeter of the bottom should be covered with concrete. This design is suitable for wells up to 10 m deep.
Option two. The finished bottom is a reinforced concrete slab, mounted on a prepared and compacted base. The quality of the installation is verified using the construction level.
Ready-made reinforced concrete bottoms are designed for loads at a viewing well depth of not more than 10 m
After performing all operations, the bottom of the well should be 5-10 cm below the lowest point of the branch pipe.
Production of a receiving tray for pipes
A layer of cement mortar is laid on the mounted bottom and a bed for drainage pipes is formed. By means of a level marks are checked.
The bottom of the finished plastic well, as a rule, already has the necessary trays.
When installing a plastic well, it is necessary to pay attention to the correct orientation of the bottom in the direction of fluid flow
Installation of the first ring of the working chamber
Drainage pipes must be laid on the receiving trays beforehand. From the bottom of the first concrete ring opposite the receiving chutes, corresponding holes are cut out.
Installation of shaped parts of the concrete well, the sealing of joints and holes is made with cement mortar grade 100.
In order to make a hole under the drain pipe it is necessary to mark and drill through holes with a drill on concrete, then knock out with a sledge hammer
The working chamber of a plastic well is mounted entirely. When there is a danger of flooding the pit, the well is placed under pressure until it is filled with soil.
To embed the pipe in a plastic well, special crowns and seals are used to ensure tightness
Installation of overlap and neck
The top of the reinforced concrete well served is a slab. The standard opening for access to the shaft of the cumulative or collector structure should be 700 mm in diameter.
The opening of the manholes is accepted from 600 mm and more: it must ensure the free entry of devices for cleaning the network if necessary.
After installation of the top of the working chamber, the installation of functional equipment for pressure drainage is carried out.
Next is the arrangement of the mouth of the well. The number and size of rings is selected taking into account the required height.
The neck of some plastic wells is a cone-shaped short pipe that can be easily cut to the required size.
The neck is covered with a support ring under the hatch.
The total height of the well must be below ground level providing a height reserve for the hatch
For a plastic well, the top and neck are the fittings mounted on the compactor.
In the case of self-production, the top of the working chamber is carried out in such a way as to withstand the weight of the soil, pedestrians, and transport, if the structure is arranged under the roadway. It is made of reinforced concrete, according to the manufacturing technology of the bottom.
Performance of a waterproofing of the working camera
In case the groundwater or flood water can come into contact with the manhole, the walls are waterproofed 500 mm above its level during the period of greatest rainfall.
For well waterproofing a bitumen waterproofing based on bitumen mastic is used;
- on the bottom and working chamber of the well;
- on cement joints, drainage pipe entry points.
Additionally, from the outside of the well the pipes are sealed with a clay lock.
Instead of bitumen mastic, you can use specialized waterproofing compounds. Waterproofing is applied to the inner surface of the well. The composition of the masonry mortar add additives that increase the waterproofing properties of the solution.
Any waterproofing has a limited service life and can vary from 5 to 50 years (+)
Finishing work: backfilling and installation of the hatch
On a mouth of a well mount manhole.
The level of installation of the hatch depends on the type of coating:
- on the carriageway - flush with the carriageway;
- in the green zone - 50-70 mm above ground level;
- in the undeveloped part - 200 mm above ground level.
Backfilling around the well is done with a gravel-sand mixture. Lay a layer of about 20 cm at a time, after which the soil is compacted. To facilitate tamping it can be shed with water.
Partial hit of the soil and vegetation layer in the backfill is highly undesirable, since it includes organic matter. Over time, organic matter will decompose and decrease in volume, and the earth around the well will sow.
Hatches for wells can be made of various materials: plastic, cast iron. It is necessary to pay attention to the load withstand, the designation “L” is light for walking paths, “T” is heavy for driveways.
Conclusions and useful video on the topic
Installation of a plastic well:
Plastic wells comparison:
The manholes installed on the drains are part of the hydraulic system. With proper design and performance require one-time service in 5 years. At the same time service life is measured in decades.
Have experience in arranging inspection drainage wells? Or have questions on the topic? Please share your opinion and leave comments. Feedback form is located below.
