When spring finally arrives, turf managers begin their agronomic practices that will prepare turfgrass for the grueling summer schedule. Pre-emergent applications, aerification, and fertilization mean another right of spring: the irrigation leak. Months of no or limited activity coupled with the changes in soil temperature reveal the weaknesses within the system that we have become so familiar with. While digging up these leaks, ringing our hands in anticipation of the cold water soon to numb our fingertips, the thought inevitably enters our heads: “There must be a better way.” Well, to that I would like to reply with “there is!”
A not so new strategy to remove these leaks from your spring playbook is available in the form of HDPE pipe. Used for decades in the petroleum industry for its leak resistance, HDPE is now becoming more popular in irrigation applications.
While many of you were anticipating what I might share that could take away your acrimony for irrigation, the mention of HDPE has probably just as quickly turned a few of you off. “What is HDPE?” “Why would I switch to HDPE?” and “how much does it cost compared to PVC?” are common questions once I start discussing HDPE irrigation renovations.
HDPE, or high density polyethylene, is a thermoplast plastic that is safe for the environment, limits product waste, and can be installed and maintained through what is known as “fusion” or a more traditional coupling method.
I’m often surprised to find out how few of us understand the variety of dangers that PVC poses on us and the world around us. PVC, or poly-vinyl chloride, is a pipe that uses dioxin in its creation. Dioxin is a known carcinogen and has been linked to numerous health issues like birth defects, neurological disorders, and a variety of cancers. Just breathing the fumes of PVC is extremely toxic. Burning PVC pipe exposes you to dioxin and chloride. While this may seem trivial to you now, will you feel that way in 20 or 30 years?
Conversely, HDPE releases no noxious gases either during its creation or during its use and potential degradation. When HDPE is burned it simply returns to carbon, a basic element that surrounds us all in our daily lives. Resistance to degradation, resistance to leaks, and environmental safety are all reasons why HDPE has been a staple in petroleum and more recently in municipal infrastructure as a potable water delivery source.
The use of HDPE is also better for the environment as very little pipe is wasted during installation. HDPE has no bells, no male or female ends. Each pipe is fused together to make a monolithic single piece of pipe. When cut, no matter the length, HDPE can be reconnected through fusion. This means that every inch of HDPE is usable. We can also create our own directional fittings. The need to order specific-sized tees, reducers and bushings is nearly nonexistent.
When installing PVC, we use pipe connected by glue or gasket. Both connections use a bell on the end of the pipe and a lubricant or solvent to assist with the connection. We “bump” the pipe together, male end to female end, and hope our precautionary preparation will reveal no leaks after pressurizing.
But what many of you may not know is that PVC has an “allowable leakage rate” from its very first day in use. You read that correctly. When studying PVC you’ll learn that it is not expected to be 100% leak free like HDPE. The connection points for PVC, be it glue or gasket, are expected to exhibit minimal leakage. This becomes more of an issue because as PVC gets older it becomes more brittle. PVC also “de-rates” with use. What that means is that as water moves through the pipe via the starting and stopping of the pump station, isolation through valves, and the on-and-off sprinkler usage, PVC loses its sustainability.
Our modern accounting principles allow us to depreciate an irrigation system. The life expectancy of pressurized PVC is roughly 15 years according to the Golf Course Builders Association of America. By comparison, we do not have such an allocated life expectancy for HDPE pipe. The monolithic fusion process of HDPE removes the couplings, creates one singular monolithic pipe, and removes pipe de-rating from the equation entirely. Most irrigation designers who are familiar with HDPE will say that it should last 40 or more years, doubling the life expectancy of PVC. In fact, those HDPE life expectations may be conservative. Doug Zak, director of sales for CMF Global, a large HDPE producer, states, “AquaFuse HDPE is rated to well over 100 years. While PVC was an amazing advancement in irrigation years ago, the attention given to water conservation and the fact that many sports turf complexes purchase water or use effluent water is enough to initiate more interest in HDPE.”
Fusion
Perhaps the biggest hurdle many sports turf managers face when discussing HDPE is the fusion process I mentioned before. While you may hate digging up leaky PVC and speculating what type of repair coupling to use, the fact that you have familiarity with it instills confidence that you are able to service and repair it.
“What if I have a leak?” is a legitimate question that every turf manager should ask. The answer is that fusion isn’t as complicated as perceived. To simplify fusion, it is simply a connection process that uses heat and pressure to connect HDPE pipe. While several fusion methods exist, the theory behind them all is that simple. Butt fusion is used in connecting pipe that has been butted up to each other end to end. A second fusion type, saddle fusion, is used primarily when changing pipe direction or pipe size. Saddle fusion does just as the name implicates, where a fitting will ride on top of the HDPE pipe like a saddle, and be fused to the pipe. Socket fusion offers a type of fusion where a coupler can be heated and pressed into the HDPE pipe. Most socket fusion is done on smaller diameter pipe.
The last style of fusion is electrofusion. Electrofusion also uses a coupler that allows the HDPE pipe to be slid into it, then uses electrical contacts to heat the coupler and pipe into the same seamless monolithic pipe just as the other styles of fusion offer. Electrofusion is the simplest and removes the experience level that can be so crucial to proper fusion. While it is the most expensive, it is also the safety net that turf managers can rely on to fix that critical leak when unforeseen circumstances, like drainage work, compromises the pipe. The electrofusion device takes the guesswork out of how long to heat or what pressure to use when pressing the HDPE pipe together.
Repairing irrigation or coupling new irrigation can also be done with special compression type fittings available in many different brands and types, among them are fittings from a manufacturer named Philmac. Using these compression fittings can serve as a huge safety net for the turf manager who wants complete control over repair and installation without implementing some form of fusion. A Philmac compression fitting tightens down on each end of the pipe, biting or gripping into the HDPE and providing a leak free connection. The only drawback to the Philmac fitting is that it doesn’t come in larger sizes; a 3-inch Philmac fitting is the largest I am familiar with. What is not commonly known is that other “knock-on” or joint restraining couplers can also be used on HDPE. The outside diameter of HDPE and PVC are the same, allowing turf managers to use traditional gasketed couplings to be used, even if it’s only temporary until some form of fusion is completed.
40-foot sticks
Whichever coupling decision you make, know that HDPE pipe comes in sticks no shorter than 40 feet. That already reduces fail points by at least half as rigid PVC pipe comes in sticks no longer than 20 feet. I have used 2-inch HDPE in 500-foot rolls on numerous occasions. This means that no or limited connection points will even be necessary. Imagine the ease of installation on a sports turf field where the majority of pipe is 3 inches or less. With the traditional pipe layout found in most football or baseball fields, HDPE quickly becomes a viable option.
No matter how much you may like something, the ultimate question we must all prepare for is “What does it cost?” The answer is not as much as you think. In the past, the cost difference was a factor. But with increased demand for HDPE, the attention given to PVC and its associated health concerns, and a better understanding of what true “apples to apples” comparisons are between HDPE and PVC pressure ratings, we see the cost difference is shrinking considerably. “HDPE resins are now about the same as PVC resins pound for pound,” says Zak.
When comparing the installed price difference between an all-fused HDPE system (pipe, fittings and valves) you have to keep in mind that 90 plus percent of HDPE systems are joined above ground, not in an open trench. This usually speeds up installation times and allows for full and complete inspection of the fusions long before it’s rolled into a trench. Fused HDPE pipe can be fully pressurized one hour after completion, as opposed to waiting 24 hours on a glued PVC joint.
HDPE also offers expandability. Hybrid systems using PVC mainlines and HDPE laterals have been a common design strategy over the last few years. This allows turf managers who are concerned with fusion as an installation or repair strategy to maintain control over their systems with traditional coupling devices for both PVC and HDPE. This could make renovations cheaper by keeping existing mainlines and marrying new HDPE laterals to the system as a temporary or permanent strategy depending on your properties wants and needs. So, when you get the irrigation repair blues remember, there may be a way to avoid it or at least minimize it. That is, unless you really like to dig holes each spring.
Ashley Wilkinson is a Professor, Golf and Sports Turf Management, at Horry Georgetown Technical College, Myrtle Beach, SC.