Choosing the right kind of pipe for any irrigation project is as important as choosing the size and type of pump, the control system and even the source of water. In simple terms, the pipe will need to be not only durable but light weight and flexible.
The longer the pipe you install can stay in place without succumbing to excessive movement, leaks and splits is a vital consideration; with more hard-wearing the pipe, repair bills will be lower and the system more efficient and dependable. In simple terms, anyone designing and installing an irrigation system needs to decide whether they want to use lines made of polyvinyl chloride (PVC) or high-density polyethylene (HDPE). The answer to this question will be dictated, in large part, by the specifics of the irrigation project, such as the source from which the water is being drawn and the size and complexity of the overall requirement. Because of this it’s useful to understand the different characteristics of each material in order to make an informed choice about the piping that's best suited to a particular installation.
Before detailing the features which differentiate HDPE and PVC it’s probably worth pointing out the properties that both materials have in common. In brief, both materials are lightweight and corrosion proof, both are a form of plastic, and both are resistant to the buildup of bacteria and chemicals. In terms of irrigation projects, the main advantage offered by both PVC and HDPE piping is that it has a higher life expectancy than traditional solutions such as iron, copper, and steel.
Although both types of piping are more durable in the long term than traditional metal pipes, there is some difference between the two. Studies have shown that PVC has a failure rating of one in 48,650 events, compared to the failure rating of HDPE, which is one in 10,000,000. In irrigation settings, failure events of this kind would generally occur because of low or high temperatures, or fluctuations in the water pressure being applied through the piping. The fact that HDPE is much more resistant to the damaging impact of the sun’s UV rays than PVC makes it a much safer choice in a climate such as that found in Florida, where extremely strong sunlight is a feature throughout several months of the year.
The greater ability of HDPE to cope with incidents and issues of this kind make it the better choice for long term irrigation projects, whereas the ease and simplicity with which PVC piping can be installed may make it the better choice for smaller projects which need to be completed at speed.
There are two ways of looking at the differences between the installation techniques required when using HDPE and PVC piping. Before examining these different viewpoints, it’s probably useful to outline exactly what those techniques are:
As stated, there are two ways of looking at this contrast. The first is to be glad that PVC piping can be installed much more quickly by any competent technician, and in any weather conditions; factors which will cut the cost of an installation and the time it takes to deliver. The other point of view, however, is that the certification needed to install and attach HDPE piping guarantees, at the very least, a basic level of competence and expertise. In addition to this, any joins in HDPE piping created through heat fusing are always going to be stronger and more durable than the PVC joins created using glue or gaskets.
PVC is the stronger and stiffer of the two materials, but the extra flexibility of HDPE makes it a better choice for projects which require a sharper bending radius in places. The rigidity of PVC makes it easier to join to some other parts of the irrigation system such as valves and pumps, but it is at these connection points where leaks are most likely to occur. The connections and fittings on HDPE piping, thanks to the heat fusing method of attachment, are far more likely to create a leak-free system, since the heat-fused joints are actually even stronger than the piping itself. The relative lack of flexibility inherent in PVC piping means that the body of the pipe is at higher risk of cracking and breaking if it is placed under stress, such as might occur when the level of the water source in which it is located rises and falls.
If the piping in question is being used to facilitate a suction line then there are some differences in the operation of that suction line which may impact on the wider efficiency of the irrigation system. An HDPE suction line, for example, is designed to float slightly above the bed of any lake or pond in which it is located. This position is important as it removes much of the risk of foreign materials or debris entering the system and causing damage.
When PVC is used, on the other hand, the intake screen assembly could settle onto the bed of the lake or pond, leading to poor performance across the pump system. The less durable nature of PVC means that small air leaks are also more likely to occur, leading to a system shut down while they are located and repaired.
Taken as a whole, HDPE piping within a system – provided it has been installed and connected by a certified and qualified technician – could have a working life of some 30 to 40 years. With PVC, conversely, the length of time over which the system works efficiently could vary wildly depending upon the diameter of the piping and the competence of the technician responsible for installation. Due to the lack of a formal certification process, sourcing a technician who can offer a guarantee of the skill levels needed to ensure longevity can be difficult, but is a key part of getting the most out of any PVC based system. To be blunt, a PVC system which is poorly installed and connected may never function efficiently in the first place, while HDPE piping, thanks to the methods required to set it up for use, is arguably more likely to have been installed correctly from day one.