The corrugated sewer system pipe can be installed in various applications, each with its own requirements. Over the years, pipe manufacturers have developed variations on the classic pipe to enable the product to adapt to various installations.
GROUND WITH OCCASIONAL PRESENCE OF WATER
In some cases, corrugated pipes have to be laid in soils where there is occasionally groundwater, the level of which fluctuates throughout the year. If the pipe has not been laid properly, such water can seep from outside into the pipe.
To overcome this problem, a hydro-expanding gasket was devised, which increases in volume when it comes into contact with liquids and occupies the entire space between the pipe corrugations and the inner wall of the coupler. It is not a replacement for the normal jointing system but should be added to the standard gaskets supplied with the pipe. The hydro-expanding gasket should be placed in the groove between the second and third rib of the pipe to stop seepage or leakage at the points where the pipes are connected.
The hydro-expanding gasket supplied by Polieco is called No Loss: it is a synthetic rubber joint with added polymers.
STEEP SLOPING TERRAIN
Italy is characterised by the presence of mountains and hills. There are many steep sloping areas where it is necessary to install a drainage system. In this type of installation, the effluent inside the pipes can reach high velocities, which can obviously increase the abrasion phenomenon in the pipeline as well as create overpressure in the end downstream manhole.
In order to facilitate the installation of corrugated pipes also in mountainous areas, a double-wall corrugated pipe was designed where the inner wall is also corrugated. The internal corrugation, in fact, allows for the slowing of the flow of water inside it, greatly reducing the risks described above.
The ideal pipe for this type of application presented by Polieco is the Slow Motion corrugated pipe, part of the Ecopal sewer system range.
CLEAR SPACE
Italian legislation identifies clear spaces, i.e. those areas where there are aquifers or areas around aqueduct wells that could be contaminated if polluting effluents were to spill into the subsoil. In these areas, one must foresee the possibility of a spill and ensure that it does not pollute the soil.
Thus, double-pipe systems were developed. The system consists of the installation of two concentric pipes separated by transverse collars or spacer strips placed on the outer wall of the inner pipe. A double gasket is inserted on the inner pipe to provide a greater watertight seal. In the event of leaks or ruptures, this system prevents soil pollution as waste water remains trapped between the two pipes.
In addition to slotted pipes, an important ally for the drainage and dispersion of rainwater into the ground is the absorbing manhole.
The absorbing manhole is nothing more than a vertically buried, slotted pipe; installation should not be too deep, so a pipe with a stiffness class of SN 4 kN/m2 will suffice.
The absorbing manhole, in order to perform its task, must have slots along its entire circumference.
The manhole can have a bottom or not, this depends on the expected amount of rainwater and the desired rate of dispersion. Rainwater storage manholes generally have a bottom that allows fluids to slowly flow into the ground through slots on the circumference. In bottomless absorbing manholes, the water tends to pour into the ground immediately, much of it will disperse vertically but much will seep through the side slots.
Rainwater manholes are therefore composed of:
Since it is a pipe, the final height of the manhole can be reduced on site with the appropriate tools to change the length of the riser as desired.
Drainage manholes combined with drainage trenches form a complete system for draining and dispersing rainwater into the ground.
The term ‘non-woven fabric’ refers to a product similar to a fabric, but obtained through an industrial process. We are therefore not talking about the classic weaving of threads in an ordinary pattern, as with knitted fabric, rather ‘non-woven’ means a random arrangement of fibres.
The fibres used are both natural and synthetic and are placed on top of each other in layers or woven and bonded together with glues, adhesives or thermal processes. Examples of commonly used non-woven fabrics are wadding and felt.
Non-woven fabric is a material similar to fabric but cheaper and more practical, as it has the following advantages:
Non-woven fabric is also increasingly being used for the drainage and dispersion of rainwater into the ground. This material, also called geofabric or geotextile, is used to prevent soil infiltration.
It is generally used to:
Geotextile can be made in a variety of weights depending on its application; the non-woven fabric for drainage must have an air mass ≥ 150 g/m2 so that it promotes the release of water but hinders the ingress of solid materials.
The manhole covers comply with standard EN 124:2015 “Gully tops and manhole tops for vehicular and pedestrian areas”.
This standard establishes the load classes, materials, construction and test principles, the marking and quality control of gully tops and manhole tops with a clear opening up to 1000 mm, for installation within areas subjected to pedestrian and/or vehicular traffic, and divided into six distinct parts:
Part 1 sets forth the general requirements that all devices made of any type of material must fulfil. Plus, depending on the type of material they are manufactured with, the manhole tops and gully tops must meet the specific requirements in Parts 2 – 6.
In 2017, all manhole top and gulley top manufacturers implemented EN 124:2015 by voluntarily applying the new certification schemes, issued by independent, accredited certification bodies, pursuant to EN ISO 17065.
In order to provide the market with guidance on the application of the standard, the Italian manufacturers and the UNI standardisation body have drawn up a technical specification UNI/TR 11671:2017 ‘Gully top and manhole covers – Guidance for the application of series EN 124:2015′.
The EN 124:2015 series of standards has not yet been published in the Official Journal of the European Union, so currently the CE marking and the drawing up of the DoP (in accordance with Construction Products Regulation No. 305/2011) are not applicable to these products.
Based on EN 124:2015, the following information must be applied in a clear and durable manner on each cover, grating and frame:
As mentioned above, as compliance with standard EN 124:2015 is voluntary, the manufacturer who obtains a product certification, issued by an independent accredited certification body, must include the marking of the body who issued this certification in a clear and durable manner on each cover, grating and frame.
The official documentation, for example the certificate of conformity, issued by the certification bodies, must include the product designation indicated below, as required by the standard:
In order to certify a manhole cover, it must pass and comply with the tests laid down in EN 124:2015 part 1 as well as the part of the standard referring to the material it is made of.
The tests must be carried out by an internationally recognised certification body and listed in the certificate of conformity.
The cable conduits feature a range of accessories that can facilitate laying or be essential for certain types of installation.
The main accessories are:
Corrugated pipe accessories are produced from plastic materials using the injection moulding technique.
The couplers and caps are polyethylene and are fitted to the ends of the pipes. Couplers are used to join two coils or bars of cable conduit so that they do not come apart; caps are used to close the end of the cable conduit. The latter product is used when you want to prevent foreign bodies from entering the pipe.
The supports are in pvc and can be single or multi-grooved. They are used as support for cable conduits and are very useful for polyfer installations where the various pipes have to follow a precise route alongside each other.
Finally, the electrical manhole is polypropylene and has a square cross-section with a cover to allow inspection inside. Electrical cable conduit manholes are used for the routing and housing of electrical cables, providing insulation from atmospheric or chemical agents as manhole as impact resistance.
Water is used daily for so many activities: washing dishes and pots, personal hygiene, watering vegetable gardens and lawns, etc.
Generally, home taps that distribute drinking water are used to do this, although potability is not necessary in these cases.
To reduce costs and preserve groundwater, rainwater collection containers can be used.
Underground rainwater collection tanks are nothing more than underground reservoirs. They can be made from structured, smooth or polyethylene spiral piping. This type of rainwater container is closed at both ends with 20 mm thick polyethylene sheets with internal reinforcements to ensure the system’s watertightness.
Rainwater collected from roofs is then channelled into the gutters and, instead of dispersion into the ground, can be stored inside the tank. Rainwater recovery tanks are in fact equipped with inlet-outlet couplings and possible hatches made of smooth and/or corrugated pipe to allow inspection inside the tank or the insertion of pumps to drain the water needed for daily activities.
Rainwater recovery tanks must be placed on a flat, firm surface suitable for the weight to be supported. The main advantage of rainwater collection tanks is that they are modular and can be adapted to specific needs: depending on the area available, even very long tanks can be connected in series or in parallel to achieve the required volumes.
The siphon gully top is a manhole installed below the drainage grates and used to collect rainwater. Their main application is in sewers and non-pressurised underground drains outside buildings (code U application area).
In this type of manhole, the presence of the siphon is fundamental as it allows the water coming from the road surface to be dispersed, preventing it from causing unpleasant odours and unhealthy exhalations, and preventing obstructive material from entering the pipe.
The gully tops can be made of plastic: Polieco’s rectangular gulley top, for example, is made of black powder medium density polyethylene (density no less than 0.930Kg/dm3). This type of product is chosen for its low weight as it facilitates laying operations and also ensures high water tightness.
Polyethylene siphon gully tops are produced by a rotational moulding process and have an outlet for the connection of plastic pipes (PEAD or PVC).
The plastic gully top can also be made with flame-retardant features if they are laid in tunnels. To achieve this variant it is necessary to use self-extinguishing material with a flammability rating of V2 according to UL94, suitable for the rotational moulding production technique.
Correct installation is essential to guarantee long life and efficiency of all construction products, therefore including manhole covers. Incorrect installation of the manhole covers, regardless of the material they are made of, can have harmful or even dangerous effects for the integrity of pedestrians and vehicles. The manhole covers must be installed by properly trained and qualified personnel, using appropriate equipment.
The manhole cover must always be in the class appropriate to the place of installation and therefore to the stress to which it will be subject. If in doubt you must use a device of a stronger class than that strictly foreseen. The designer must also choose a size appropriate to the clear opening to guarantee safe access.
Furthermore, before installation, the following indications must be checked:
As for the choice of material for the bedding, if the road is closed off during installation, cement mortar with characteristic compressive strength (Rck) greater than or equal to 50 N/mm2 can be used, respecting the curing times prescribed by the manufacturer.
If the road needs to be opened to traffic quickly, the manhole covers must be placed on materials for quick hardening installation with the following minimum features:
When the level of the manhole cover housing on the pits needs to be raised, a shimming material can be used with a minimum compressive strength of 50 N/mm2, it must have lasting durability and be compatible with the installation materials intended to be used.
Shimming materials are generally made of cast iron, steel or concrete. It is not allowed to use hallow bricks, broken tiles, pieces of wood or plastic or anyhow any type of material which does not provide the necessary strength and durability features.
The contracting company performing the job first of all must make sure that the pit, prefabricated or built on site, is intact and capable of structurally bearing the weight of the manhole cover to be applied.
It is also essential to make sure that the frame and the installation seating on the pit are clean by eliminating any traces of mud, grease or debris. If necessary, the top of the pit could be roughened to improve the hold of the laying material.
The depth of the housing chamber must be made taking account of the height of the devices to be installed, to avoid using shimming materials as much as possible. The width of the housing chamber must be at least 1.6 times the maximum external size of the frame of the device to be installed, so that a consistent and uniform concrete kerb can be made around it.
It is recommended to mix the laying material mechanically and not by hand so that it is homogeneous: the operation must be carried out as quickly as possible and anyhow before quick hardening.
Immediately after applying the laying material, the frame must be positioned promptly at the correct height, centring the clear section of the frame with that of the pit and exerting appropriate pressure on the bedding to guarantee a firm grip, making sure that no internal part of the frame overhangs the pit. The frame must not be positioned directly on the top of the pit.
The frame must be positioned on the bedding so that its bearing surface is appropriately supported by the top of the pit/chamber. When installing the cover in the presence of heavy and/or frequent vehicular traffic, it is recommended to anchor the manhole cover frame to the concrete slab or wall of the underlying concrete pit, positioning the fastener plugs in the specific circular slots in the frame. Furthermore the frame must be positioned at road level using appropriate reference points and so that it is level with the surrounding surface.
Make sure there are no empty spaces between the manhole covers and pit; pay special attention when applying the laying material near the cover seating so that residual material cannot deposit. It is also necessary to make sure that the laying material covers the flanges of the frame with at least a 1 cm width and comes out of any holes or slots on the frame, providing a perfect grip.
Beddings thicker than 4 cm should be applied at two different moments: the first layer should be 2 to 4 cm thick, while the following layer should only be applied after having placed suitable primer material in between. Make sure to leave sufficient residual thickness for the finish of the road surface. The exposed surfaces of the bedding, both inside and outside the frame, must be smooth and made even.
The manhole covers must be inserted carefully into the frame only after the material has a sufficient grip and compressive strength and only after a careful check and cleaning of the support surface of the seal and of the seating of the frame where the cover must be inserted.
The finish filling around the manhole cover must be carried out after at least 3 hours with the same laying material, leaving a layer of at least 3 cm to allow the finish of the road surface by laying asphalt. Make sure no compacting devices pass over the manhole cover to avoid damaging the bedding/frame/cover system. The installation must not be subject to any type of stress until the bedding material has reached sufficient strength. After installation, the frame and cover/grating must be level with the road surface.
Before opening the area where the manhole cover is located to traffic, the curing times supplied by the manufacturer of the product used must be respected: if there are no different indications, it is necessary to wait at least 72 hours.
Corrugated cable conduits 450N and 750N are manufactured and tested in accordance with EN 61386-1 and EN 61386-24. With reference to these standards, each European country issues its own product marking: two examples are the IMQ marking in Italy and the NF marking in France. Cable conduit pipes are manufactured in accordance with the “Directive 2014/35/EU relating to electrical equipment designed for use within certain voltage limits” and CE-marked, so they do not fall under the ‘Construction Products Regulation’ nr. 305/2011.
Cable conduits must be identified with a durable and legible marking applied to the surface of the conduit every 1 to 3 metres.
The marking in accordance with EN 61386-1 and EN 61386-24 must contain the following information:
The tests required by the above-mentioned standards and often stated in the corrugated pipe data sheet are:
The main characteristics for the choice of corrugated pipe for regulation electrical installation are resistance to compression and impact.
Compressive strength is the most important characteristic since the pipe is buried and consequently subjected to the overlying static load. On top of this there may also be any load due to above-ground stresses such as the weight of vehicles. As defined by the standard, the corrugated cable conduit sample is crushed between two plates so as to deform the inside diameter by 5%; the force required to achieve this crushing must exceed 450N or 750N.
While compressive strength is a property that accompanies the cable conduit during its life, the impact test, on the other hand, serves to guarantee the duct during installation. The test simulates the accidental stresses caused by stones in the ground falling onto the surface of the structure during the burial phase. Therefore, the soil layer adjacent to the cable conduit should be free of stones larger than 80-100 mm in diameter. To test this characteristic, the sample, conditioned for 2 hours at -5°C, is hit by a dart with a fixed weight of 5 kg from a variable drop height depending on the nominal diameter of the corrugated pipes (300 to 800 mm height). At the end of the test, there must be no gap allowing water to pass from the inside to the outside.
The main characteristics of a micro-slotted drainage pipe are that it collects excess water and evacuates it. For the first function, it is necessary that they have slots such that ground water can enter the pipe along the entire drainage line; while for evacuation, it is necessary that the pipe has a sufficient cross-section that it is free of occlusions and that it is laid with a slope such that the water can transit.
In rainwater drainage pipes, collection is ensured by the slots in the pipe itself. The slots in a micro-slotted pipe can be arranged around the entire circumference (at 360°), or only on the top (at 220°), allowing the bottom surface to collect water as it is free of slots. The width of the slots is crucial to the purpose of a drainage pipe: it must be narrow enough to prevent large particles from entering the pipe, which could result in clogging, quickly rendering the drainage function ineffective. While the slots must also need to be wide enough to allow water to flow out fairly quickly. It has been found that the ideal slot width of a drainage pipe is 2 mm.
The slots can be perpendicular to the pipe or longitudinal or diagonal to the axis of the pipe. With slotted pipes, the slotting must be in the corrugation groove so that the two peaks of the corrugation prevent the surrounding material from obstructing the slot. The combination of the thickness together with the length of the perforation allows the slotted drainage pipe to act as a filter, thereby separating the water from the suspended silt-soil.
Polieco produces different types of corrugated drainage pipe: