Peter Monro, agronomist with the NZST, believes that performing a regular tune-up and warranty of fitness will get the best out of your irrigation system
W
hen that expensive pop-up irrigation system was installed into your bowling green it is likely that the club would have
thought it would be there forever or, at least, outlive the club! For most systems the only visible evidence of that investment are the sprinklers. This is because most of the system (i.e. pipes, wires and valves) is buried in the ground and the head-works (pump and controller) are hidden away in the shed. That old saying “out of sight, out of mind” is possibly the cause of why things can start to go wrong. Many clubs who install the systems themselves to save money often don’t have an as- built plan or record of the infra-structure. This can lead to confusion in later years as to the exact location of the components of the system. That aside, we often take for granted normal ageing and degradation of a system’s various components (e.g. sprinkler nozzle wear that can cause inferior water pressure), which can sneak up on us overtime without us realising it. Before we know it, we start to see some common symptoms of poor turf performance such as wet areas that never go away, dry patches, root diseases, weeds, moss and algal slime - the list goes on. Interestingly, most of these ongoing problems can be rectified just by conducting some simple checks or performing a tune up on your irrigation system. In this article we look at simple checks and solutions to improve irrigation performance that leads to better performing turf. So, let’s do a tune up and warrant of fitness on your sprinkler system.
Sprinkler coverage and uniformity
Irrigation engineers would argue that the fundamentals of good sprinkler coverage and uniformity do not occur by accident. Correct operating pressure, sprinkler spacing and nozzle size are paramount. Sprinkler spacing is fixed on bowling greens at
approximately 18 metres around the circumference of the green, so, in theory, should not really be an issue. However, sprinkler pressure is very important for optimal break up of water across the green surface. Therefore, it is a good idea to periodically monitor the dynamic water pressure.
So what should the sprinkler pressure be and how do we check it?
First and foremost, the operating pressure should not be measured at the pump as some people would believe. The reading on the gauge at the pump generally does not represent the true pressure at the sprinklers because of friction losses in the pipes. Irrigation engineers recommend a minimum operating (dynamic) pressure directly from the sprinkler of 70 psi (480 kPa). The best way to measure the pressure is with a Pitot gauge device. Each sprinkler should be measured this way. If the operating pressure is too low there may be one or more inherent problems causing this. Often it is a process of elimination when trying to get to the source of the problem. We tend to look for simple things first, such as the control valve setting or function. Another consideration would be the pump. If you run a booster pump, or rely on your own pumping system, you may have a problem with
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