HDPE pipe is becoming more popular for use on golf course irrigation systems, with more than 50 percent of new systems utilizing HDPE mainlines and an even higher percentage using HDPE laterals. HDPE pipe works well, but only when properly designed, specified and installed. As with any product, it had some initial issues.
For starters, some systems were specified with too low a pressure rating in the pipe. Then, there were failures of new HDPE systems in Florida – dubbed “polygate.” We learned you need pipe with a pressure rating higher than the operating pressure and then some — no different than PVC.
Contractors, distributors and designers learned the hard way you cannot weld a high-pressure rated fitting to a low-pressure rated pipe and the wall thicknesses needed to match up, which, in most cases, required machining the fittings. The industry also learned that HDPE pipe does not like chlorine or high temperatures in the soil. And, lastly, side fusion for HDPE laterals came and went. Time provided an education and most of these issues are no longer a problem. When it comes to HDPE, it’s all good ... or maybe it’s not.
As the above issues have faded and HDPE pipe systems seem “bulletproof,” some contractors are pushing the envelope and not necessarily in a good way. They’re pushing the limits of the pipe and/or taking advantage of what it will let you do even if it’s not in the course’s or irrigation system’s best interest.
Because HDPE pipe is fused, you can join together very long lengths. There really is no limit, especially when you are doing 2-inch laterals. HDPE pipe is also easily installed by pulling as opposed to trenching using (hopefully) the proper equipment. If you have the right soil and enough horsepower, you can pull very long lengths. HDPE is very flexible, especially at smaller sizes so you can make turns easily — too easily. On the adjacent picture, the red line indicates the installed pipe routing. You can see the contractor put a sprinkler at the front right of the tee (as you play) and continued their pipe pull of the 2-inch pipe down the slope out into the rough, making a 180-degree turn with the pipe and then going back up the slope to the tee to install a sprinkler at the left front of the tee. No fittings, all pipe. Most likely the radius of the turn was based on how quickly the machine could turn. You could never get away with this with PVC. HDPE allowed it and the result is a bad practice, at best, and a poor quality installation as a fact. In this case, the superintendent even questioned how the contractor could do that and wondered if the pipe broke, how would he fix it. The answer? He wouldn’t. It would be unfixable with that much curvature in the pipe. If it was PVC, there would have been elbows used and all the pipe would be up on the edges of the tee, not in the rough like it was shown on the irrigation plan and how the HDPE should have been installed.
Just because the pipe will let you do such things, there is no reason to do it. Instead, it weakens the pipe and lowers the integrity of the entire irrigation system. All pipes have curvature limits, velocity limits and pressure ratings, and they should be adhered to. HDPE, as good as it is for certain applications, shouldn’t be taken advantage of because it is too good.