PVC versus Poly Pipe

PVC versus poly pipe
Learn the best type of pipe to use when installing an in-ground sprinkler system that will last you a long time.

So you’re getting a sprinkler system for your lawn and landscape – good for you! What type of pipe will the contractor be using? If the answer is ‘sprinkler pipe’ or ‘I don’t know,’ you need to pump your brakes. The type of pipe used in your sprinkler system will go a long way towards determining the useful life of that system.

There are only two choices: PVC or Polyethylene. Which is better for our Northern Virginia area? In a word (technically an abbreviation) PVC. Folks who install poly systems will argue the point but let’s compare.

Pressure Ratings

The standard 1″ PVC pipe used for lawn sprinkler systems is rated to withstand 200 pounds per square inch (PSI). Comparable 1″ poly pipe is rated to withstand 100 PSI. In fact, to achieve the same pressure rating as PVC, the walls of poly would have to be twice as thick.

The fittings (where pipes are joined together) for PVC are rated at 450 PSI. Poly pipe uses squeeze clamps or saddle fittings which are unrated.

Cold Weather Tolerance

Poly pipe is flexible where PVC is semi-rigid. This enables poly pipe to hold up better in extreme cold. Measuring the low temperature brittleness, poly comes in at a whopping negative 130 degrees Fahrenheit. PVC withstands only up to minus 40 degrees Fahrenheit. This is a big advantage much further north. Not so much in Virginia where the record all time low is nowhere near minus forty.

Water Flow

The inside diameter of 1″ poly pipe is much smaller than 1″ PVC (in fact, 1″ poly can fit inside 1″ PVC). This, along with the type of fittings used on poly pipe, restricts water flow and degrades hydraulic performance.

These are all measurable differences that can’t be denied. The debate continues though (it’s worth a Google). For my money (yes, PVC systems cost more to install), it’s PVC all the way. For thirty plus years I have installed all PVC pipe systems. I have never had to replace a pipe that failed. I have also serviced hundreds of poly pipe systems over that time and have rarely seen one more than 5 years old that didn’t have leaks.

The biggest problem is at the fittings (where pipe, heads or valves are attached). Poly pipe uses a combination of ‘squeeze’ fittings (a hose clamp that tightens the pipe pushed over a nipple point of attachment) or ‘saddle’ fittings (where a barb is punched through the poly pipe and the saddle rests on the outside). They create weak points that eventually leak under pressure.

True, PVC fittings can leak if they are incorrectly installed. PVC pipe comes in twenty foot lengths and has to be joined together with glued fittings. With several hundred feet of pipe needed for an average system, in addition to attaching valves, heads, etc… that’s a whole bunch of fittings! If glued together properly though, the PVC fitting is actually stronger than the pipe. Poly pipe fittings on the other hand, even if installed perfectly, create a weak point in a pipe that is already two times weaker than the PVC. Boom! Mic drop.

If you’re considering getting an in-ground lawn sprinkler or need expert advice from a licensed irrigation contractor, reach out to our team today. At BG Outdoor Services, we’ve been designing, installing, servicing and repairing lawn irrigation systems since 1988. Contact us today for assistance with your lawn irrigation needs.

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