TANK SIZING

Use the following information to calculate the proper size of the tank:

RAINWATER YIELD (R)

Projected roof surface (S)

Theprojectedroofsurfaceisequaltothe

building’s base, regardless of the shape

and roof inclination.

Precipitation values (Vp)

Local precipitation value indicates the

annual rain quantity. Such information is

usually available from the local authority

or at the nearest meteorological station.

(average: 1,000 l/m

2

)

Roof cover value (Vt)

WATER REQUIREMENTS (FI)

WC

Household cleaning

Other

TOTAL WATER REQUIREMENTS (FI)

Values to consider for large systems:

........................

+

........................

+

........................

+

........................

+

........................ =

Roof manufacturing material

Value

Tiles in clay, terracotta and glazed

0,9

Roof in cement or slate

0,8

Flat roofs with gravel

0,6

Green roofs

0,5

R = S (m

2

) x Vp (litres/m

2

) x Vt

Utility

Average requirement

per year

No.

WATER REQUIREMENTS (FI)

9.000 litres

x

........................ people

=

Washing machine

5.000 litres

x

........................ people

=

Gardening

1.000 litres

x

450 litres/m

2

........................ people

=

x

................................. m

2

=

...............

x

.......................................

=

•

School = 1000 l/person

•

Office = 1500 l/person

The calculation factor (FC) is the smallest value of the rainwater yield (R) and the water requirement (Fi).

The constant (K) is 0.0625.

The minimum volume of the tank (V) then will be:

V = FC (litres) x K

Before installing the rainwater recovery system, we recommend you to contact the local council or local authority to

find out the local

standards in force (where present) concerning the treatment of rainwater for domestic use (use of debacterising systems, rainwater

separation from drinking water, etc.).

13

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