Often, the reasons for choosing one type of pipe over another are not black and white. In one case recently in rural Oklahoma, the reason was blue.
Contractors and utility officials in Water District #10 in Delaware County, Okla., had always used PVC pipe for their water systems, in part because it was available in blue for easy identification in the ground. When a manufacturing members of the Plastics Pipe Institute developed a solid blue high-density polyethylene (HDPE) pipe for potable water applications, the battle between HDPE pipe and PVC pipe was on. In the end, HDPE was selected for this particular application.
"We looked at both HDPE pipe and PVC pipe and decided that the best choice for the district for the long-term was the polyethylene," said Tim McCrary of Crafton, Tull & Associates Inc, an engineering firm.
Although the availability of the product in blue got HDPE in the game, the color of the pipe doesn't help pay back the district's loan--the selling of the water does.
Water officials in Oklahoma discovered that the less water that leaked from the pipes, the more efficiently they could sell it, which in turn helps pay back the loan faster.
"Environmental concerns were among the criteria we used to pick the pipe material," McCrary said. "When your only revenue stream is your water, you have to protect that as much as possible. There's been a big crackdown here on the issue of water loss. We concluded that the HDPE pipe gives us the best chance at protecting this valuable source."
Heat is on
Unlike PVC, polyethylene pipe, in both solid blue and traditional black with the blue stripe, provides a leak-free system through its joining process--heat fusion--that produces strong, totally sealed connections.
Further, polyethylene is a dielectric material and is frequently used as an insulating material for electrical conductors. Because it is a non-conductor, polyethylene is simply not subject to corrosion.
"Municipalities with traditional piping systems all have a minimum allowable 'unused water' percentage that they tolerate," said Rich Gottwald, executive director of the Plastics Pipe Institute. "In many municipalities, this water loss can reach 30% to 50%, or more.
"However, many municipalities are now using HDPE pipe to construct a leak-free and corrosion-resistant water distribution system to deliver water to their residents--and are avoiding the problems and costs associated with leaky systems," added Gottwald.
The other criteria the Oklahoma Water District used to evaluate PVC and HDPE pipe included cost; operational issue and performance; regulations; future development of the area; and public and environmental concerns.
HDPE scored equal to or better than PVC for this application in each of those categories, according to the engineers.
The cost factor was tied into the long-term performance. Engineers conducted a study that projected leaks, breaks, and pipe/joint failure over a 15-year period and calculated potential lost water. Again, HDPE pipe was predicted to save more money over that period of time.
Another factor in the decision was the success contractors in the area had with polyethylene natural gas lines. Polyethylene pipe is used for more than 90% of the fuel as distribution piping in the U.S. because of its reliability, leak-free performance and resistance to corrosion.
"We've always encouraged water officials to learn more about HDPE pipe and its ability to provide the durable performance they want," said Gottwald. "After all, if polyethylene pipe is trusted by the fuel gas industry to be leak-free, what's stopping the water industry?"
With a plethora of new construction projects in Delaware County, the sewer lines also will be a major part of the area's development.
"When it's time for the sewer pipes to go in, we'll be on the lookout for the HDPE pipe," McCrary said.
