Using PVC as a material for a fluid piping installation carries out implicit economic, safety and versatility advantages regarding a lacking in maintenance.

We avoid calcareous incrustations in piping, so that we maintain the section where the fluid runs constantly and we decrease the risk of obstruction.

Moreover, this material’s accessories have a very smooth inner surface, what decreases significantly the loss of energy charge and consumption of the tapering facilities.

1. Evacuation


This European regulation specifies the requirements for pipes and accessories in poli(vinyl-chloride) channeling systems, intended to be used inside the buildings as well as buried inside the buildings structures (marked with “BD”).

The test parameters to which this regulation is referred are also specified.

This range of accessories is designed to evacuate any kind of waste and rain water in buildings, except water coming from facilities with long duration drains at a high temperature, for example, industrial laundries PVC-U accessories are not recommended.

2. Description of an evacuation system

An evacuation net must be able to transport rain water coming from natural rains outside of a building without polluting as well as sewage coming from the use of sanitary devices (washing machines, showers, sinks, toilets, etc…)

For the evacuation of this water, net internal pipes can be designed in three different ways which lead to the three internal distribution systems.

Unitarian system


This system is designed for the common collection of waste and rain water in the same down pipes or sewer pipes.

Its simplicity and economy can be highlighted as advantages, but presenting as a disadvantage that its measuring must foresee atmospheric precipitations.

Due to this disadvantage, when these precipitations are not produced, sewer pipes are over measured so the risk of producing deposits and sediments increases.

The danger of syphonage also increases when precipitations are significant and down pipes substantially increase their flow, since there can appear hydraulic cylinders that need a more energetic ventilation. This system is not recommended for buildings with more than 6 floors.

Separative system


In this system, the evacuation is made through two independent channeling, so diversions, down pipes and sewer pipes are different for waste water and rain water.

This system requires a double net in most of the street as well as double connection in every land.

From the technical point of view, this system is the most appropriate. Nevertheless it is not used too much because of its expensive cost and, a lot of times, due to the fact that separative sewage systems do not exist.

Mixed system


It is the most used system in which derivations and down pipes are independent for waste and rain water. Both nets are unified in common sewer pipes gathering them together in one channeling.

This system is the simplest one regarding installation, since just one sewage channeling is needed in every street and just one connection in every land.

It is an intermediate solution between the unitarian and separative system that partially reduces the disadvantages of every pure system.

We can take into account the following classification for accessories and pipes in a sanitary installation:

3. Aspects to take into account when carrying out an installation

Ventilation of the installation

Ventilación de la instalación

Ventilation is a key factor for the proper functioning of the evacuation net. If it is not enough, there causes the communication between the pipes inner air and the local sanitary air, therefore this air is polluted.

The cause of this effect is the formation of hydraulic cylinders due to the accumulation of discharges.
This phenomenon consists of the appearance of a hydraulic piston that compresses the air of the lower part of the installation, generating an overpressure.

At the same time, on the top of the installation there will appear a depression which creates a suction effect in the installation. The smaller diameter of the downpipe is and the biggest flow wastes that it collects; the hydraulic cylinders’ formation is intensified.

As a suction consequence, traps get empty, so they break the hydraulic closing letting bad smells go through.

This effect is intensified when it rains, since the risk of hydraulic cylinders’ formation is greater, as the normal discharge flows are added to the rain flows.

Bad smells can also be perceived during summer, through terraces and courtyard drains, due to the lack of hydraulic closing of the traps because of the water evaporation, thus, in this case, it is convenient to frequently fill them with water.

The ventilation net needs lower pipes diameters than the ones used in the evacuation net. A relationship of approximately 3/5 can be established. The material used can be the same as the one used in the small evacuation net.

Overpressure and depression effects caused by the hydraulic piston

Overpressure and depression effects caused by the hydraulic piston

In order to avoid the appearance of these effects, the drainpipe must be ventilated by having a pipes net parallel to the evacuation net which communicates with free-air pipes. Therefore, the atmosphere air can come in the installation achieving equalize the channeling pressures with the external one. In order to have a proper ventilation of our evacuation net, we can use one of the four ventilation systems which solve the problem according to its importance degree.

Primary ventilation


In this type of ventilation, an extension of the down pipe is made in order to communicate it with the outside through the building roof, so that the pipe is in contact with the external atmospheric pressure.

Primary ventilation is mandatory in all installations, having as advantages simplicity and economy, but it has as a disadvantage that it does not solve the compression phenomenon. This system is enough for installation up to 6 floors, with short drain splits (smaller than 5 m) and with independent traps for every device with a minimal closing level of 5 cm.

Secondary ventilation


The secondary ventilation implies the primary ventilation, and it consists of installing a pipe of generally lower diameter, parallel to the enlarged down pipe.

This secondary pipe crosses also the roof, so it is in contact with the atmospheric pressure and it communicates with the down pipe under all the floors.

Thus the suction effects in higher floors and the compression effects in lower floors are avoided, so this system is suitable for buildings up to 15 floors with drain splits (smaller than 5 m) and with trap closings higher than 5 cm.

This kind of ventilation shows as a disadvantage the increase of installation costs and space.

Tertiary ventilation


This ventilation model implies the primary and secondary ventilation.

It consists of totally ventilating traps and drain traps through some pipings that communicate with the ventilation down pipe, as well as all toilets by the higher part of its trap. Therefore, it achieves totally cancelling all break problems of the hydraulic closing.

This system should be used when drain splits are longer than 5 meters or when the building has more than 14 floors.

4. Calculation of sanitary pipes’ diameter

In order to choose the diameter of the splits from which the installation is formed, we must carry out the necessary calculations in order to find the balance between functionality and economy of our installation.

In the determination of sanitary pipes diameters, the usual hydraulic formulas cannot be used, since, if we tried to do it in a rigorous mathematical way, we would have an excessively complex hydropneumatic problem due to the fact that these pipes do not work with the complete section.

For all these reasons, a base unit called discharge unit has been fixed. It encompasses in its concept the flow and the simultaneity or frequency of use, so the diameters are stablished based on the experience of existing sanitary installations.

The discharge unit (DU) is defined as the quantity of water that a simple device as a private-use sink with a pipe exit of Ø30mm can evacuate and has a value of 0,47 L/s.

Therefore, it is equivalent to a sink capacity and it allows us to express according to this unit which we can look up in Table 1.

Table 1. Discharge units and minimal pipe diameter

Device Private use Public use Private use Public use
Toilet 4 6 110 110
Bidet 2 3 40 40
Bath 3 4 40 50
Squatting late 8 110
Suspended urinal 2 40
Vertical urinal 4 50
Kitchen sink 3 6 40 50
Washing machine 3 6 40 50
Dishwasher 3 6 40 50
Dispenser 1 1 32 32
Shower 2 3 40 40
Spillway 8 8 110 110
Sink 1 2 32 40
Sink for clothes 3 50
Likewise, we can also see the minimum diameter for the recommended drain of each device: Occasionally, this diameter is oversized in order to prevent blockages due to solid objects’ falls.

As discharges can vary according to the use of the installation, two kinds of installations are stablished based on its use:

  • Private use: home installations
  • Public use: Installations where there is no limit of persons, nor uses times.

Each pipe of the installation must have a diameter whose drainage capacity in discharge units is equal or higher than the total of devices that flow into.

In the Table 2 we can see the drainage capacity of the tubes according to its nominal diameter:

Table 2. Drainage capacity of the tubes according to its nominal diameter

1% 2% 3%
1 1 32
2 3 40
6 8 50
11 14 63
21 28 75
47 60 75 90
123 151 181 110
180 234 280 125
438 582 800 160
870 1150 1680 200
If there is a joint, the pipe exit must have, at least, as drainage capacity as the total amount of discharge units coming from the entry pipes.

The down pipes’ diameter to be used is obtained by taking the highest value of the ones obtained, taking into account the maximum quantity of DU in the downpipe and the maximum quantity of DU in each pipe based on the number of floors.

The Table 3 indicates the necessary diameter for the downpipes according to the exposed conditions:

Table 3. Necessary diameter for the downpipes

Maximum number of DU, for a height of downpipes of: Maximum number of DU, in each pipe a height of downpipes of: 
Up to 3 floors: More than 3 floors: Up to 3 floors: More than 3 floors:
10 25 6 6
19 38 11 9
27 53 21 13
135 280 70 53
360 740 181 134
540 1100 280 200
1208 2240 1120 400
2200 3600 1680 600
3800 5600 2500 1000
6000 9240 4320 1650

In the downpipes that discharge toilets, a diameter lower than ø 110 mm must not be taken. More than 3 floors:

Horizontal sewer pipes of waste waterare measured in order to work midsection up to a maximum ¾ section, under uniform flow conditions. The sewer pipe diameter based on the maximum number of DU and the gradient can be extracted from Table 4.

Table 4. Sewer pipe diameter based on the maximum number of DU and the gradient

1% 2% 4%
20 25 50
24 29 63
38 57 75
96 130 160 90
264 321 382 110
390 480 580 125
880 1056 1300 160
1600 1920 2300 200
2900 3500 4200 250
5710 6920 8290 315

5. Dilatations during the installation

PVC suffers changes in its physic properties as it is exposed to temperature changes. When temperature increases, it reduces its viscosity, thus its length increases. The lineal expansion coefficient of this material goes from 0,07 to 0,08 mm/m ºC, this means that when temperature increases 1ºC, a 1m pipe will measure 1,00007m. This value does not represent significant changes on the size, but when there are longer sections as well as higher temperature variations, these changes start to be relevant, so we need to take precautions.

On one hand, we can use unions with an elastic joint as the ones used in the sliding coupling with an expansion joint, which can absorb length changes. They must be installed, at least:

  1. In downpipes that cross concrete slabs, one on the accessory that collects water in every floor.
  2. In downpipes with fixed points, one on each fixed point.
  3. In downpipes without fixed points, at least, one every 4 meters.
  4. In horizontal assemblies, at least, one every 4 meters.

We can also make normal changes in the pipes direction, which provide us an appropriate means to compensate the expansion if the temperature variation is too big.

The situation of a fixed point FP can be calculated through the minimal length of the bending side LMIN.

More information

Calculational determination of the bending side length (LBS)

Sliding points SP are points which hold the pipe at the same time that enable its horizontal movement as a consequence of expansion.


We calculate the minimum bending side length (LBS) with the following formula:



LBS=bending side length in mm.

ΔL = expansion in mm. It is calculated with:         

K = PVC constant (33,5)

Ø = Pipe external diameter in mm.

α = PVC-U expansion coefficient (0,008 mm/m°C)

ΔT = Temperature variation between fluid temperature and room temperature.

In some cases, it can be necessary to turn to expansion loops in order to absorb length changes.


6. Internal quality control of the manufacturer according to the UNE-EN 1329-1 regulation

The accessories made by IBIDE FITTING PLASTIC S.L. are subjected to a quality control during the manufacturing process and once the final product is finished, in which the controlled characteristics are monitored with some tests and at a frequency established in the next chart:

Test and Frequency

Average external diameter on the male hook side Minimum every 4h/finishing of the machine
Average internal diameter on the entrance
Body and entrance thickness
Entrance lenght
Visual analysis
Heat performance For each manufacturing period. At least once a day
Vicat temperatura determination At least once a month

A. Visual analysis

In the visual test, as the test is carried out without increases, inner and outer surfaces of the accessories must be smooth, clean and without grates, ampoules, impurities, holes and any other surface imperfection that may prevent accessories from satisfying the regulation.


B. Dimensional analysis

In the dimensional analysis, average diameters, densities and lengths are measured, so they must be in accordance with the tolerances given by the following table:

Diameters, densities and lengths

DN Average external diameter on the male hook side (dem) Average internal diameter on the entrance (dsm) Entrante lenght and male hook Maximum ovulation Wall        thickness Entrance thickness
dem, min dem, max dsm, min dsm, max L2,miny L1,min Omax emin e2, min
32 32,0 32,2 32,1 32,4 22 0,77 3,0 2,0
40 40,0 40,2 40,1 40,4 26 0,96 3,0 2,0
50 50,0 50,2 50,1 50,4 30 1,20 3,0 2,0
75 75,0 75,3 75,2 75,5 40 1,80 3,0 2,0
90 90,0 90,3 90,2 90,5 46 2,16 3,0 2,3
110 110,0 110,3 110,2 110,6 48 2,64 3,2 2,4
125 125,0 125,3 125,2 125,7 51 3,00 3,2 2,4
160 160,0 160,4 160,3 160,8 58 3,84 3,2 2,4
200 200,0 200,5 200,4 200,9 60 4,80 3,9 2,9
250 250,0 250,5 250,4 250,9 60 6,00 4,9 3,7
315 315,0 315,6 315,5 316 60 7,56 6,2 4

Measures in millimeters.

C. Heat behavior


It consists of suppressing complete molding to a certain temperature T, in a ventilated heater during a given time, depending on the wall density. Molding surfaces are tested before and after the heating, and all welding fissures, bubbles, laminations and holes are measured and expressed in percentages of wall density. The percentages obtained must be in accordance with the requirements specified in that regulation.


D. Vicat temperature determination


The principle of the method consists of defining the temperature at which a normalized penetrator of a 1mm2 calibrated surface, subject to a 50 N charge, enters 1mm in a cut test tube surface of the wall of a tube or an accessory, when the temperature increases at a constant speed of 50 C/h. The temperature in centigrade degrees, when the penetration is 1 mm, is called Vicat softening temperature (VST).

7. Recommendations for transport, storage and placement on site of PVC accessories

It is recommended, when carrying out any operation of load/unload, transport and storage of PVC accessories or tubes, to have the appropriate means and the necessary precautions in order to avoid to harm the product with the consequent quality loss.

7.1. Recommendations for transport

Accessories are supplied in their original packing, which is the best preservation place until they are used, whereas tubes are normally supplied in pallest by the manufacturer.

Load and unload operations in the vehicles for its transportation must be done without dragging, shaking or hitting the load and carrying out this operation in an ordered way.

Caution measures to be taken when transporting this product can be sum up in four points:

  • Vehicles designated for this goal must be conditioned in such a way that they have a horizontal flat area without any element which may damage or hit the load.
  • The placement of the load in the transportation vehicle must be carried out placing it orderly on the area aimed to it, without using any fixation elements such as cables or chains which may damage the product. The use of elastic tapes is recommended as long as the excessive crush that may deform the load is avoided.


  • Unload operations must be orderly carried out, avoiding hitting or dragging the goods.
  • During the transportation of the goods, placing heavy loads on them must be avoided, so that deformations do not occur. Such godos must not stand out the lorry’s platform.


7.2. Storage recommendations on site placements

  • Goods shifting must be avoided at the minimum, so it must be stored the nearest as possible to the working place. The area designated to store the product must be flat and leveled in order to avoid deformations that may be permanent as well as it must be well ventilated. We cannot locate it near solvents, adhesives, fuels, paints or cutting objects that may degrade the product.
  • Due to PVC fragility at low temperatures, tubes and accessories must be prevented from hits with any type of object if we are under these conditions. Moreover tubes and accessories made with this material must be protected from direct solar radiation, especially in summer. Storage near heat sources must be also avoided, preventing the temperature of the external surface of the pipe or accessories to reach 45ºC.
  • Tubes must be stored by stacking them alternating the cups and letting them standing above, so that they are supported on all their length.
  • It is recommended, when carrying out any operation of load/unload, transport and storage of PVC accessories or tubes, to have the appropriate means and the necessary precautions in order to avoid to harm the product with the consequent quality loss.


8. Conditions to be accomplished by the evacuation internal network

If our evacuation net has successfully been installed by following the given recommendations, a good working quality will be guaranteed thanks to the accomplishment of the following conditions:

We will quickly achieve the evacuation of water used in different services and especially the evacuation of water proceeding from toilets.

The access of polluted air proceeding from the evacuation net in inhabited premises is avoided by means of the hydraulic closing made by traps, which will maintain at least 5 cm of water thanks to the installed ventilation system.

A total water tightness of the net will be maintained in every point, so an elastic hermetic seal in gaskets and joints, which will admit net movements without losing its impenetrability, as well as movements generated by system expansions, which will be avoided by making normal changes of pipes direction.

Thus, we will block internal retained waste that may block the piping because of the smooth inner walls offered by the PVC.

An accurate fastening of all net accessories will be achieved by avoiding possiblelandslides and vibrations which produce annoying noises due to the discharges impact.

Therefore, all materials integrating the net evacuation will have such a quality that will enhance low maintenance expenses as well as a similar duration to the one calculated for the rest of the building.

9. Preventive maintenance recommendations for a evacuation network

IBIDE recommends a preventive maintenance of the net evacuation in order to avoid possiblewaste water or gas leaks that may endanger the building’s and its occupants’ healthiness. This maintenance and its periodicity can be sum up in this Table.


Elevation pumps revision O
Non-accessible covered manholes and sinks cleaning O
Downpipe sump boxes cleaning O Foreseeing revision upon bad smell
Sink manholes cleaning O
Inspection chamber cleaning O
Gate manholes cleaning O Foreseeing revision upon bad smell
Traps and  valves   cleaning Maintaining permanent water in order to secure the hydraulic closing
Drip boxes cleaning  O Foreseeing revision upon bad smell
Hugh sewer pipes  revision O
Sinks and drain traps cleaning O Maintaining permanent water in order to secure the hydraulic closing