Claber

The basic principles of water

To irrigate properly, it is first of all necessary to have a grasp of the basic principles governing the behaviour of water.

These principles are eternal, unchanging and valid in all circumstances – from a simple drip system for terrace plants, to an underground system with multiple circuits in a large park.

When you know the physical properties of water and the units of measure used, you’ll be able to choose the Claber products and solutions most suited to your requirements, to design the ideal type of project and look after your garden with greater awareness, not to mention efficiency. To become acquainted with these principles, all it takes is a few facts and a few minutes of your time.

Pressure:

Imagine that you pour all the water contained in your system into a container with a cylindrical shape. The weight exerted by this column of water on the base is the pressure. The units of measure used include BAR, kPA, water column m, atmospheres and PSI.

1 BAR = 100 kPA = 10m water column = 0,987 ATM = 14 PSI
Flow:

This term defines the quantity of water passing through a vessel in a given unit of time, measured in litres/minute or m3/hour. It is important to know that the smaller the diameter of the hose, the lesser the flow and therefore the quantity of water actually distributed to the plants in a given unit of time. Flow may also vary according to the type of hose material (PVC or PE).
System Diameter l / minute m3 / hour
Aboveground (PVC hose) 1/2" (12mm)
5/8" (15mm)
3/4" (19mm)
1" (25mm)
14,92
23,32
37,42
64,79
0,895
1,399
2,245
3,887
Underground (PE hose) 3/4" (19mm)
1" (25mm)
41,46
70,08
2,487
4,204
Drip (PE hose) 1/4" (4mm)
1/2" (12mm)
1,65
17,52
0,099
1,051

HEAD: In a circuit, water is pushed by a pump, the power of which is measured in HP. Head is the difference in height (in metres) of the water column.

FLOW RESISTANCE: The loss of pressure due to surface friction and the variation in fluid direction; the longer the hose, the greater the flow resistance. This factor must always be taken into account when designing an irrigation system.

PRESSURE LOSS IN BAR
(for 10 m hose)

litres/second litres/minute internal diameter of hose
 
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0,9
1
 
6
12
18
24
30
36
42
48
54
60
D 12,5 mm 1/2" D 14 mm 5/8" D 16 mm 5/8" D 20 mm 3/4" D 25mm 1"
0,0772 0,0448 0,0236 0,00809 0,0027
0,2712 0,1574 0,0829 0,0284 0,0097
0,5653 0,3281 0,1728 0,0592 0,0202
0,9520 0,5525 0,2910 0,0997 0,0341
1,4262 0,8278 0,4360 0,1493 0,0511
1,9845 1,1517 0,6066 0,2078 0,0712
2,6238 1,5228 0,8021 0,2747 0,0941
3,3418 1,9395 1,0216 0,3501 0,1199
4,1367 2,4009 1,2646 0,4332 0,1484
5,0067 2,9058 1,5306 0,5243 0,1796