An irrigation system relies on water pressure for efficiency. The water pressure at source will be higher than at any other part of the system. Measuring irrigation system pressures at different points can indicate the delivery rate for the water in specific zones.
Step 1 - Decide Which Pressures You Need to Know
If there are obvious problems with an irrigation system you will have a good idea of where pressure is a problem.
Step 2 - Understand Supply Side Problems
If there are problems in the supply side of an irrigation system, you need to take pressure readings along the system. There are several pressure gauges available that can be connected into a system and give accurate readings.
Step 3 - Interpret the Readings
Initial supply side readings will tell you the pressure at which the water is being supplied from the utility company main. This pressure cannot be influenced without creating more problems. Supply side readings taken along the irrigation system can indicate major problems.
In theory, an irrigation sprinkler system operates in much the same way as an electricity supply system. As long as all the pipes are full the supply at any given point will be the same as that at any other point. Variations in pressure will indicate that water is being lost in quantity.
An irrigation system that is pressure-fed is subject to changes in the conditions of pipes and fittings. If a main pipe gets compressed or folded over, the pressure of the water could be greatly reduced beyond the compression. Although the initial reaction might be to imagine a loss of water, what has actually happened is that the access to the water has been lost – not the water itself.
Step 4 - Check Soil Penetration of Water
A major problem with irrigation systems is that the pressure that should be measured is the pressure within the soil. Soil which is highly colloidal will react differently to soil which is not. The colloidal soil will indicate increases in internal pressure and reduction in electrical resistance as more water is absorbed but that is not an indication that the irrigation is successful. Water held in a colloid is not always available to the plants that need it. Soil that is not colloidal will allow free passage of water and show very little change in internal pressure.
Step 5 - Check Water Pressure Within Plants
Just as important as the pressure of water within the irrigation pipes is the pressure of the water within plant stems. It is possible to measure this pressure but only in laboratory conditions. Plants do give an indication when they have a low water pressure, they start to wilt. As pressure gauges, plants give a very accurate indication of where the irrigation system is failing.
The various pressures that reflect the efficiency of an irrigation system can be measured or assessed to quite an accurate degree. How the pressures are interpreted will have a direct impact on how the system is operated.