- Type of storm sewer
- Storm drainage elements
- Storm drainage scheme
- Calculation of system parameters
- Installation of storm sewers
The storm sewer is designed to drain rain and melt water from the house itself, as well as from the garage, paths and hard-surfaced areas. What type of sewer to prefer, what functional elements to make, how to independently plan and install such a system, we will tell in this article.
A storm sewer is needed to drain rain and melt water from the foundation of a house, outbuildings and a yard. The largest drainage area – the roof – should be equipped with gutters and downspouts around the perimeter, from which water enters the storm sewer – a drainage system, which is a network of canals with elements of the system.
Type of storm sewer
Depending on the type of channel laying, the stormwater can be:
- mixed type.
Linear consists of surface gutters placed along the paths and covered with a decorative grill. The gutters can be made independently of concrete, as well as assembled from purchased products – steel, concrete or plastic, lined up with sealing joints. The branching of the gutters can be significant, being collected by separate branches from buildings and paths into a common collector.
Spot sewerage means a single receiver from each downpipe, covered with a grate, after which the water enters the underground sewerage pipeline. Pipes from individual point water intakes are also collected in one line.
Point storm sewer
The mixed type is used if, along with the linear network, there is a need to perform separate point water intakes located away from open gutters.
Storm drainage elements
The composition of the storm sewer network is determined by whether you intend to use rainwater (for example, for irrigation), clean it or discharge it into the general drainage system without unnecessary manipulation.
The system can include the following elements:
- Open trays (linear part).
- Rain hoppers (point part).
- Door pallets (can be made as a point rainwater inlet).
- Sand traps.
- Inspection well.
- Drainage pipes.
- Closed part of the sewage system.
- Sewer hatches.
Purchased linear sewer trays and storm water inlets are easy to install, have stable geometry, and are compatible with other elements. The cost and resource depends on the material, correct installation, climate. In private houses, trays are installed in class A (pedestrian zone) and B (car zone) according to the load. Choose the right length to minimize the number of joints.
Plastic tray with lattice
Trays and gullies are covered with grates for aesthetic reasons, for safety and as a coarse filter from large debris. Grilles can be cast iron, plastic or steel.
Plastic and concrete storm water inlets
Sometimes water is drained from the downspout through an open concrete gutter
The door trays have a container for collecting water, which does not drain anywhere. If a visor is installed above the door and there is little water, then such a device is convenient. If there is no visor or slope towards the storm trays, it is better to install a storm water inlet.
Sand traps are used to trap sand, earth, grass and other debris falling into the storm drain. Without these devices, the pipes will quickly overgrow, and you will have to deal with their cleaning. Products are made of plastic, steel or concrete and according to the load class they must correspond to the trays.
Plastic trash box
An inspection (inspection) well is required to monitor the condition and, if necessary, clean the channels. They equip it in places that are tense from the point of view of hydrodynamics: connecting side hoses, sharp turns, on especially long straight sections (35–70 m depending on the diameter according to SNiP) – where clogging is more likely. The device is a lidded reservoir or shell.
Inspection well – installation
Drop well – when the depth of the pipeline is changed
Homemade concrete well
Accumulative collectors are a purchased or home-made reservoir, if necessary with an additional filtration system or, if the storm sewer is connected to domestic wastewater, a biological treatment system. After the collector, the wastewater can be used (irrigation, household needs), diverted to its own pond, the nearest reservoir or general drainage system (permission is required).
Drainage pipes with holes collect excess moisture from the soil and drain it into the storm drain, if a separate drainage system is not provided on the site.
Drainage pipes with perforation
Pipes for distribution can be made of PVC or HDPE, completely smooth or two-layer, with an outer corrugated part. Pig-iron and concrete pipelines are almost never used for these purposes. Pipe class – for outdoor sewerage. We will tell you about the calculation of the pipe diameter below..
The materials of the system must be selected taking into account the strength, inertness to corrosion, resistance to mechanical damage and temperature changes, ease of installation, and service life.
Storm drainage scheme
Before performing the work, it is necessary to draw a future network, determine the installation locations of its elements, make a list and estimate of upcoming purchases.
The scheme is developed from the points of discharge to the collector or drainage well. The open and closed part of the route is applied to the site plan, the network drops along the laying depth, the places for the installation of sand traps and wells are indicated. The diameters and lengths of pipes, the number of branches, connecting elements are determined, the volume of excavation and installation work is outlined.
1 – garage; 2 – revision well; 3 – drainage tray with a grid; 4 – house; 5 – storm water inlet; 6 – door pallet; 7 – sand collector; 8 – HDPE pipes; 9 – perforated drainage pipes; 10 – tank for collecting and purifying rainwater
The scheme may include additional elements: plugs, siphons, check valves (manifold piping).
Advice! When working out the scheme, take into account the laying of other communications and pipelines on your site. They shouldn’t interfere with each other..
Calculation of system parameters
For normal operation, storm drains determine:
- discharge water consumption;
- pipe diameter;
- pipeline slope;
- laying depth.
The discharge of the discharged water depends on the area from which the water is removed and the intensity of precipitation (according to SNiP-2.04.03–85, Table 4). The volume of discharged water is calculated according to the formulas for rain and melt water, in detail, taking into account the correction factors set out in Section 3 “Methods for calculating the volumes of organized and unorganized runoff”, Kaluga, 2011 (there is a calculation algorithm in SNiP, but more complicated).
In general, the calculation formula looks like this:
- Q is the volume of water that the system must remove;
- q20 is the intensity of precipitation;
- F is the area of surfaces from which water is planned to be diverted;
- ? – correction factor, depending on the material of the covering of the site from which water is collected.
The costs from each stormwater inlet when merging with other streams are summed up, the pipe diameters become larger. In practice, for individual sections of the storm drain of a country house with a plot, pipes O 100-150 mm are taken, for the main line – O 200 mm.
Slopes of channels, trays and pipelines are taken according to SNiP-2.04.03-85, which determines the minimum values for:
- O 150 mm – 0.008 (8 mm per 1 running meter);
- O 200 mm – 0.007 (7 mm per 1 running meter).
For individual trays of any section, the minimum slope is 0.005 (5 mm per 1 running meter). Some reinforced concrete products immediately have the desired slope, indicated by an arrow.
In practice, it is desirable to make the slope more than the minimum: 15–30 mm per 1 running meter. m.
The depth of laying the domestic storm sewer is less than the drainage, if both networks are installed on the site, and averages 30 cm.
Installation of storm sewers
The scheme has been worked out, calculations have been completed, all elements of the system have been purchased. At the first stage, gutters and pipes are mounted on the roof..
The next step is to mark the future system on the site: with a tape measure, pegs and ropes. Having outlined the laying of the route and the installation of a sand trap, wells and a collector, they begin earthworks.
Linear sewage trays, laid on paved paths, are mounted taking into account the preparation of the cushion so that their upper edge does not protrude above the tiles, asphalt or cobblestones (the level of the drained surface). The trays should be installed in a dug and tamped trench on a sand or sand-cement substrate. So the product will be securely fixed and will last longer. After installing the trays, the joints between the individual segments are sealed and the entire channel is covered with a grid.
Layout of the drainage tray: 1 – sand cushion; 2 – concrete base; 3 – soil; 4 – artificial base; 5 – asphalt concrete pavement; 6 – drainage tray with lattice; 7 – thermo joints (bitumen, sealant); 8 – paving slabs; 9 – leveling layer; 10 – base
Important! When laying trays, do not forget to determine the slope towards the collector with the level.
Simultaneously with the trays, according to the scheme, sand traps are built into the system (at the inlet of water from the tray into the pipe) and inspection wells.
Storm inlets are mounted, to which a knee is attached at a slight slope, and closed piping with fittings is performed to the collector or water discharge point. Closed piping is laid in dug trenches on a sand cushion.
When connecting the storage collector to the network, you need to make sure that it is dug below the level of the pipelines and is thermally insulated with a layer of sand and gravel.
Before covering the wiring with sand, tiles, earth or turf, it is necessary to carry out hydraulic tests, find leaks and eliminate them. Only after a positive test result the system closes.
The plot is beautiful, the house, buildings and paths are protected from excess moisture!