The maximum desirable pressure is 200kPa. In some circumstances a
pressure reducing valve may be required to prevent high pressure leaks.
4.1.3
Low Pressure Supply
The water supply can be from a mains system or a special storage tank. The
supply pressure should be between 10kpa (1 metre head) and about 50kpa (5
metre head). The supply is normally a tank that is refilled at regular intervals.
A 1000 litre tank will replace about 750mm of evaporation. The tank capacity
that you need depends on the expected evaporation at your site, and when you
can conveniently refill the tank.
Automatic Evaporation System
SITE REQUIREMENTS AND LAYOUT 17
Reticulated
water mains
Shut-off valve
Model 6529-2H
High Pressure Solenoid
(10-100kPa)
mounted in enclosure
Suppply hose with
valve at tank
1000 litre supply
tank on stand
Optional hose from
drain pump. Enters
top of tank to prevent
siphoning.
1 metre
head
Model 6529-2L
Low Pressure Solenoid
(0-70kPa)
mounted in enclosure
4.1.4
Underground Supply
Where the water supply is scarce or inconvenient, it is possible to install a
tank large enough to be self-sustaining at most sites. Any excess rainfall
captured in the pan can be recycled back into the storage tank. A roof over the
tank can be used to capture additional rainfall. If required, the tank can be
buried and a small pump used to refill the pan.
The expected annual evaporation and rainfall, and the monthly distribution
can be estimated from published data from your national weather office. This
can be used to design the capacity of your supply tank.
UNIDATA
18 SITE REQUIREMENTS AND LAYOUT
Low level roof with gutters
to capture additional rainfall
Fill pump substituted
for solenoid
Drain pump hose outlet
configured to prevent
siphoning from pan
Buried tank for water supply
Ground
level
