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How do we know High-Density Polyethylene Pipe (HDPE) is safe to use for Drinking Water?
What is HDPE pipe?
High-Density Polyethylene or HDPE pipe is a commonly produced, flexible plastic pipe made of thermoplastic high-density polyethylene widely used for low-temperature fluid and gas transfer. The strong molecular bond of HDPE pipe materials helps it to be used for high-pressure pipelines. HDPE plastic is one of the most versatile of plastics—used in everything from hard hats to house wraps—it's also widely recycled, in both its rigid form (e.g., containers), and flexible form (e.g., polybags). Polyethylene pipes have a long and distinguished service history for gas, oil, mining, water, and other industries. Due to the low weight and high corrosion resistance of HDPE pipes, the industry is growing tremendously.
What is HDPE made from?
HDPE pipes are made by the polymerization of ethylene, a by-product of oil. Various additives (stabilizers, fillers, plasticizers, softeners, lubricants, colorants, flame retardants, blowing agents, crosslinking agents, ultraviolet degradable additives, etc.) are added to produce the final HDPE pipe and components.
What is the history of HDPE pipe use?
In the year 1953, Karl Ziegler and Erhard Holzkamp discovered high-density polyethylene (HDPE). Solid-wall HDPE pipes began replacing metal pipes in oil and gas systems in the late 1950s. In the early 1960s, gas utilities started replacing failing iron pipes with HDPE pipes, and because of its success, 95% of all new gas distribution systems installed today use HDPE. Soon after, HDPE pipes began to be used in agricultural drainage systems. In the 1980s, HDPE began to replace metal and concrete in stormwater culverts. HDPE is the insulation coating on the overhead telephone and electrical lines. HDPE is the same substance used in bottle caps, reusable water bottles, plastic lumber, patio furniture, hula hoops…the list goes on and on.
Is HDPE pipe considered “Food Safe”?
HDPE pipe is a common industrial plastic that is highly utilized in modern applications. Federal Regulation oversees the use and service of HDPE. The FDA considers HDPE pipe to be “approved food grade - BPA Free” (aka ANSI/NSI 61) and is approved for potable water applications. The molecules of HDPE are more tightly packed and stable than other food-grade plastics, meaning less plastic can leach into your food. The safest food-grade containers/buckets made from HDPE have the #2 symbol stamped on them, which indicates the plastic is considered safe from any BPA leakage. There has been no evidence of any widespread health problems associated with the use of HDPE in food and beverage or drinking water applications.
Will Sunlight affect HDPE pipe?
Sunlight contains ultraviolet rays that reduce the tensile properties of plastics with time. Usually, 3-5% carbon black is added to HDPE to make it UV resistant, which turns HDPE pipes black in color. HDPE pipe is installed in the ground, covered with at least 18” of ground cover, and not subjected to UV rays. This UV protection allows HDPE to be used in telephone and electrical wires that are consistently exposed to UV light, without any loss of tensile strength.
Will gasoline or wildfire affect HDPE pipes?
Gasoline does not adversely affect HDPE. The material does not soften or lose strength when exposed to gasoline. However, HDPE pipes will burn if exposed to an outside fuel source (i.e., gasoline). This could happen if there was a large fuel spill adjacent to the pipe. However, the fire would extinguish itself quickly due to the lack of an air supply and the fact that the pipe is buried.
Why did we choose HDPE pipe?
• The durability of HDPE is one of the benefits of HDPE. It has 100+ years of useful life.
• HDPE saves money because it is inexpensive compared to ductile iron pipe or copper. Currently, HDPE is less than half the cost of Ductile Iron Pipe.
• HDPE is superior to metals. It is lighter, flexible, and doesn’t fracture due to freezing.
• HDPE is efficient to produce. It requires less energy to fabricate, transport, and install than metal alternatives.
• HDPE won’t rust or fracture. It is resistant to corrosion and scaling.
• HDPE is rigid enough to hold its form over time, even in a seismically active area, and it is flexible enough to bend around corners and under creeks or streams.
• Installation of HDPE pipe is often “trenchless,” meaning that the new pipe can be pulled through the old pipe, and the road does not have to be “open cut.”
• 20-foot sections are joined using butt fusion, making a longer section of pipe that is effectively seamless.
• The seamless HDPE pipe is essentially leakproof and has a longer life than ductile iron pipe because there are no joints to slip or allow root intrusion.
• HDPE is better for our employees, too. It’s so light, one person can carry a 20- foot section, and it won’t break or hurt someone’s foot if it’s dropped!
• Using flexible HDPE typically means no ugly trenches or damaged driveways, streets, sidewalks, or landscaping.
• Best of all, replacing old mains with HDPE saves you money! The design, purchase, and installation of HDPE are significantly more affordable than Ductile-Iron pipes. This means your water rates go further.
What about microplastics? Will using HDPE pipe cause me to be exposed to microplastics in my drinking water?
Microplastics are plastic pieces between one micrometer (one-millionth of a meter) and five millimeters in size. Nanoplastics are even smaller than one micrometer. 35% of all microplastics come from synthetic fibers (i.e., fleece) released during clothes-washing. Another 30% comes from car tires. Plastic breaks down over time, especially when exposed to the atmosphere and UV light for long periods of time. HDPE pipe is protected from breakdown by the black carbon that blocks UV light and the fact that the pipe is buried and not exposed to the atmosphere.
Wait, I have heard about plastic pipes before, don’t they break easily?
The polyvinyl Chloride (PVC) pipe material introduced in the 1970s led to an unacceptable leakage rate. This type of pipe was prone to splitting and is not the same as the HDPE plastic pipe we use today.
Is there a situation where HDPE pipe is not a good choice?
HDPE pipes can work satisfactorily in a wide temperature range of -220 F to +180 F. However, the use of HDPE Pipes is not suggested when the fluid temperature exceeds 122 F (50 C).
Would you like more information on Trenchless Installation of HDPE?
Check out these videos:
Information for this FAQ has been collected from these resources:
The Plastics Paradox, Facts for a Brighter Future, Chris DeArmitt, PHD