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Wavin AS+
Technical Manual
Phone. +31(0)38 42 94 951
Rainwater collecting pipes/calculation
Rainwater collecting pipes are subject to a filling factor of
h/di = 0,7 and a minimum fall of 0.5%.
This sizing is calculated subject to rules similar to those
governing the layout of waste water collecting pipes.
Rainwater underground and collector pipes/calculation
The hydraulic sizing of the rainwater underground and col-
lector pipe should take into account the part of the roof area
that provides effective drainage surfaces for the outside
of the building, subject at least to the two-year calculation
period selected for the surrounding land (duration level “D”),
according to the provisions of sections 14.9.2 and 14.9.3 of
DIN 1986-100. The larger cross-section at the point of least
structural tension resulting from roof drainage is to be taken
into account with respect to the direction of flow until the
calculation resulting from the two-year calculation period
extends the cross-section.
The sizing of rainwater underground and collector pipes is cal-
culated subject to rules similar to those governing the layout
of underground and collector pipes for sewage.
The following waste water standards also apply.
Inside the building:
Minimum diameter DN 100
Filling factor h/di = 0.7
Minimum fall J = 0.5%
The following applies outside the building:
Minimum diameter DN 100
Filling factor h/di = 0.7
Minimum fall J = 1: DN
The minimum flow rate is 0.7 m/s
The maximum flow rate is 2.5 m/s
Dimensions can include complete filling without excess
pressure upstream of a drain shaft with open flow.
Installation
The installation of rainwater pipes is subject to similar criteria
to those that apply to the installation of sewage pipes inside
and outside buildings.
Additional criteria such as dew-point prevention and thrust
resistance should also be taken into account. Please refer to
the section on rainwater pipes
Mixed-water pipes
Mixed-water systems use a common pipe for waste water
and rainwater, running from the building or its surrounding
land. As with underground and collector pipes, the minimum
diameter of the mixed-water pipe is DN 100.
Calculation
The sizing of mixed-water pipes is subject to the relevant
mixed-water discharge rate Qm, which is in turn based on the
respective proportions of waste water discharge Qww and
rainwater outflow Qr, using the equation
Q
m
= Q
ww
+Q
r
Whereby
Q
m
is the mixed-water discharge rate, in litres
per second (l/s);
Q
ww
is the waste water discharge rate, in litres
per second (l/s)
Q
r
is the rainwater discharge rate, in litres
per second (l/s)
The sizing is calculated subject to rules similar to those gover-
ning underground and collector pipes.
Mixed-water pipes outside buildings are subject
to the following:
Filling factor h/di = 0.7
Minimum fall J = 1: DN
Minimum flow rate = 0.7 m/s
Maximum flow rate 2.5 m/s
