HDPE Again

A few months ago I revisited the discussion of 2-wire (decoder) versus conventional control systems because there had been some changes/improvements to 2-wire technology. Along those same lines, it’s time to revisit the dreaded (for some) HDPE vs. PVC conversation.

HDPE has come a long way since the “polygate” debacle earlier this decade. Designers and suppliers, not to mention manufacturers, know much more about the characteristics and limitations of HDPE and its fittings. We still do not know as much as we do about PVC, but we have come a long way since 2010.

First, we have learned you do not use HDPE pipe with low-pressure ratings; it doesn’t have much strength; and it does not match up to the fittings correctly.

Second, we know you don’t use HDPE in highly chlorinated systems and high-temperature environments.

Third, we know the fitting rating and the pipe rating need to be pretty close to the same. And the fittings need to be machined to where the wall thickness’s match up so they are the same. Sounds like common sense, but back in the day that wasn’t necessarily being done.

Few systems today are installed with all PVC pipe. Many are installed with all HDPE pipe and many are installed with PVC mainlines and HDPE laterals. Depending on who you talk to, PVC mainlines and HDPE laterals may be the most common scenario.

With HDPE laterals, you get rid of the solvent weld-cemented (glued) joints, which is a good thing as they start to fail 10 to 25 years after installation. With PVC mainlines, you get a nice price point versus an all HDPE system. There are golf courses that should be all HDPE pipe, as well as golf courses that don’t need to be all HDPE. But not everyone agrees. There are designers out there who think you always use HDPE pipe regardless of the soil or course conditions!

Fittings have improved in strength and variety, a big reason why HDPE laterals are the norm today. No longer does everything have to be a saddle. Many, if not most, installations now use compression couplings on the laterals. Compression couplings had their issues a few years ago but are now very reliable. There are a variety of different saddles from different manufacturers available for the mainlines and laterals. People continue to try and innovate, not necessarily with success. For example, take the brief use of “side-fusion” fittings for attaching the swing joint to the lateral pipe on HDPE laterals. Other changes with HDPE have been allowing coiled pipe for smaller sizes. Coiled pipe requires less fusing (every 300 feet vs. every 40 or 50 feet) and less labor, but the contractor does need to use a straightener to take the inherent bend out of the pipe before installing it.

PVC pipe continues to be a strong choice for mainline piping. Besides its lower cost, people are familiar with it, it can be repaired by golf course staff and there are a wide variety of well-proven fittings available. Unless you put a backhoe bucket through it, a mainline very rarely breaks these days.

Every golf course is different and every irrigation system should be different to match the golf course. As a result, base the decision on pipe type on the golf course and the available budget for capital improvements and maintenance. When properly engineered (pressure rating and velocity), either PVC or HDPE, or a combination of the two, will serve the irrigation system and you well.