COLLEGE OF ENGINEERING AND ARCHITECTURE

DEPARTMENT OF ARCHITECTURE

RWS MT 01: “STORM DRAINAGE SYSTEM”

DATE GIVE: Feb 11, 2023

DATE DUE: Feb 18, 2023
DATE SUBMITTED: Feb 18, 2023
REFERENCES:

STUDENT: LAPADA, JESSA S.

SUBJECT: AR-BU 1 L&S I
BUILDING UTILITIES 1 - PLUMBING AND SANITARY SYSTEMS
INSTRUCTOR: AR. AIZA FERNANDEZ & AR. JOEVAN RONA
Stction 1101- GENERAL

Storm drainage are required for roof areas, courts and courtyards to collect
stormwater and discharge the stormwater to an approved point of disposal
not in conflict with other ordinances or regulations.

1102 I Materials:

1102.1.1 Rainwater downspout or conductor piping placed within the interior of a

building inside a ve11ical pipe chase or nm. within a vent shaft shall be of
cast iron, galvanized steel, iron. brass, copper, lead, Schedule 40 ASS,
0\VV, Series 1000, PVC DWV or other approved materials.

1102.1.2 Rainwater downspout or conductor located on the exterior side of a low

height building shall be not less than 26 ga. galvanized sheet metal. The
bottom of the conductor draining over the catch basin storm drain or storm
sewer is protected from damage by connecting a stronger material such as
steel pipe or cast iron at its lowest section.

1102.1.3 Rainwater piping located within a medium height building basement area
shall be of galvanized iron pipe, Schedule 30; cast iron soil pipe, S.W.~
Type DWV copper tube~ Schedule 40 ABS, DWV, Series 1000, PVC
DWV, or other approved materials.

1102.1.4 Downspouts for high “rise buildings shall be of stronger pipe materials to
resist the high hydrostatic pressure inside the vertical downspout installed
within the pipe chase which has no intermediate branch from the roof to
the ground level.

1102.1.5 Rainwater piping commencing 0.6 meter from the exterior of a building
may be of suitable approved materials permitted in the Installation
Requirements of this Code.

1 to 2.2 Connections and Installation

1102.2.1 Rainwater piping shall not be used as soil, waste & vent pipes.
1102.2.2 Rainwater piping installed in locations where they may be subjected to
damage shall be protected.

1102.2.3 Roof drains, overflow drains, and rainwater piping used in a building
construction shall be previously tested and accepted in conformity with
the provisions of this Code.
Section 1103 - ROOF DRAIN
1103.1 Materials
Roof drains shall be of cast 1ron, copper. or other corrosion-resistant
materials.

1103 .1.1 Strainers

1103.1. 1.1 Roof drains shall be equipped with strainers extending not less than 102
mm above the surface of the roof immediately adjacent to the drain,
Dome-Type Strainers shall have a minimum total net inlet area of one and
one-half ( 1 1/2) times the area of the outlet pipe to which it is connected.

1103.1.1.2 Roof deck strainers for use on sun decks, parking decks and similar
occupied areas shall be an approved flat-surface type which is level with
the deck. Such drains shall have a total net inlet area not less than two (2)
times the area of the outlet pipe to which the drain is connected.

1103.1.1.3 Roof drains passing through the roof into the interior of a building shall be
made watertight at the roof level by the usc of C.l. drain with integrallv.
cast waterstop ring around the outside of body and plaecd at mid-depth of
the concrete roof slab and the installation of a clamped suitable flashing
material around the drain.

1103.1.1.4 In all cases the outlet connections are in inside-caulk or female screwed.

Section 1104- SIZING OF RAINWATER PIPING

1104.1 Vertical rainwater piping shall be sized in accordance with Table 11-1,
which is based upon maximum depth in mm or rainfall per hour falling
upon a given roof area in square meter. Consult local rainfall figures to
determine maximum rainfall per hour. Normally, a 102 mm hour rainfall
intensity is used around Manila area.

1104.2 Vertical Wall Areas. Where vertical walls project above a roof so as to
permit storm water to drain to adjacent roof area below, the total roof area
considered may be computed from Table 11-2 as follows:

1104.2.1 For one (1) wall - add fifty (50) percent of area of the wart to the roof
area,

1104.2.2 For two (2) adjacent walls ·- add thirty five (35) percent of the total wall
areas to the roof area;
1104.2.3 Two {2) walls opposite each other and of same heights - add no additionnl
area to the roof area;

1104.2.4 Two (2) walls opposite of differing heights- add fifty (50) percent of wall
area above top of lower wall to the roof area.

1104.2.5 Walls on three (3) sides - add fifty (50) percent of area of the inner wan
below the top of the lowest wall, plus allowance for area of wall above
top of the lowest wall per Sections 1104.2.2 and 1104.2.4

1104.2.6 Walls of four (4) sides- no allowance for wall areas below top of lowest
wall - add for areas above top lowest wall per 1104.2.1, 1104.2.2,
1104 2.4 and 1104.2.5

1104.2.7 The area of the side of a tall building exposed to rain is taken as one-half
of the gross area.

 Round, square, or rectangle rainwater pipe may be used and are considered equivalent
when enclosing an inscribed circle equivalent to the drain leader diameter.
 For manila and evirons, a rainfall intensity of 102 mm per hour is used.

1104.3 Horizontal Rain water Piping: The size of a building rainwater piping
or any of its horizontal branches shall be sized in accordance with
Table 11-2 (Based upon maximum roof areas to be drained.)

Example: Table 11-2

Roof Area- 548.1 m^2
.Max Rainfall/hr. ·- 127 mm
Pipe Laid at (20.9 mm/m) slope or s = .02

Find area in column under 127 mm and at slope of 0.02 and read 561. 1 m^2 (as
closest). choose 152 mm as size of leader and downspout at leftmost column

1104.4 Roof Gutter. The size of semi-circular bottom roof gutters shall be based
on the maximum roof area, in accordance with Table 11-3
Example: Table 11-3
Roof Area = 186 m^2
Max Rainfall/hr. = 102 mm
Pipe Laid at 10.4 mm/m slope or s = 0.01

Find area in column under 102 mm rainfall intensity on Table with s = .01 and
read 181 .4 m^2 (as closest) move to left and read 177.8 mm diameter gutter.

1104.5 If the rainfall is more or less than those shown in Table 11-2 and ll-3.
then adjust the figures in the 50.8 mm rainfall by multiplying by two (2)
and dividing by the maximum rate of rainfall in mm/hour.
Example:
In Table 11-2 with a 10.4 mm/m or s = .01 and a 203 .2 mm rainfall, find the
number of square meter a 102 mm pipe diameter will carry.
Solution :
2
2 x 349.3.=87.4 m
8
Notes:
l. The sizing data for vertical conductors, leaders. and drains is based on the
pipes flowing 7/24 full
2. For rainfall rates other than those listed, determine the allowable roof area by
dividing the area given in the 25 mm/hour column by the desired rainfall rate.
3. Vertical piping may be round, square, or rectangular. Square pipe shall be
sized to enclose its equivalent round pipe. Rectangular pipe shall have at least
the same cross~sectional area as its equivalent round pipe, except that the ratio
of its side dimensions shall not exceed 3 to I.