32
Wavin AS+
Technical Manual
Phone. +31(0)38 42 94 951
Collecting pipes
Collecting pipes are defined as any type of installed pipe
designed to take up waste water from single or collecting col-
lection pipes and downpipes. Collecting pipes are preferable
to underground and collecting pipes for installation inside
buildings, as they are easier to inspect, clean and maintain.
Calculation
Hydraulic specifications
Filling factor h/di = 0.5
Minimum fall J = 0.5 cm/m
Minimum flow rate 0.5 m/s
Upstream inward volume flow from a waste water pump
station, filling factor h/di = 0.7
Collecting pipes are subject to the equation:
Q
tot
= Q
ww
+ Q
c
+ Q
P
Q
tot
describes the total flow of waste water from the drainage
system.
The total waste water discharge (Q
tot
) includes both waste
water from sanitary drainage points (e.g. showers, toilets
and wash basins, etc.) and the amount of water from “con-
tinuous” drainage points (Q
c
), such as condensate from air
conditioning systems or drainage from swimming pools. The
total waste water discharge also includes volume flows from
pump stations (Q
P
).
Sizing of the collecting pipe should take into account both
the calculated total discharge of drainage water and the
maximum discharge unit (DU). This is clarified by the example
shown below.
Sanitary drainage points connected to the collecting pipe.
1 x wash basin (DU = 0.5)
1 x WC with a 4.5-litre cistern (DU = 1.8)
Waste water discharge Qww is calculated as follows:
Q
ww
= 0.5 x √(0.5+1.8) = 0.76 l/s
As the discharge unit for the WC (1.8 l/s) is greater than the
calculated waste water discharge of 0.76 l/s, the collecting
pipe should be configured on the basis of 1.8 l/s.
Note
If total waste water discharge Q
tot
is less than 2.0 l/s, the
collecting pipe can be sized using Table 10 of this manual
(“Sizing of secondary-ventilated collecting pipes”). If the total
waste water discharge is more than 2.0 l/s, sizing should be
based on Table 10.
Underground and collector pipes
These are usually directly connected to downpipes or to
drainage sources installed in the basement of the building.
They are buried under the floor of the building or installed in
its foundations.
Collecting pipes should be chosen in preference to under-
ground and collector pipes for installation inside buildings.
This does not apply to buildings without a basement. In these
cases, the underground and collector pipes leading out of the
building should be kept as short and as straight as possible.
Underground and collector pipes with a minimum nominal
diameter of DN 80 (Wavin AS+ = DN 90) may be connected
to the nearest transfer shaft outside the building if hydraulic
calculations permit.
If toilets with water-saving measures (flushing volumes of 4 to
4.5 l/s) are in use, check in each case to ensure that the self-
cleaning performance of pipes with nominal diameters of 100
or more is ensured.
Examples of corresponding criteria include:
Nominal diameter of the collecting pipe and underground
and collector pipe
Fall
Number and type of connected drainage sources
Simultaneity of waste water drainage
Bends measuring ≤ 45° must be used for changes of direc-
tion in underground and collector pipes or collecting pipes.
Branches must be connected to horizontal pipes at an angle
of ≤ 45°.
