Buried Utilities-Locator Tape/Wire

[sugarbare10]

Installation of PVC pipe mains & service piping, it is common practice to place locator or detect tape or wire in the trench over the pipe. At what depth is it typically placed? I've seen it placed 12" below grade, marking pipe below, but can't reflect the true location of the pipe. If wire is used, is there a problem if it is taped to the top of pipe? What type & size of wire, insulated or bare, copper or aluminum should be specified?

 

[SACPEengineer]

It should be dictated by your local city/county water & sewer specifications, something like “all distribution and transmission system piping and appurtenances shall have a continuous reinforced copper tracer wire secured to the pipe to prevent separation during and after installation...”.
If not, develop and provide specifications to the contractor, like in the link here: [URL unfurl="true"]http://mrwa.com/PDF/TracerWireSpecGuideFinalweb2.pdf[/url]

 

[bimr]

See the attached for installation details on tracer wire.

 

[rconner]

While I'm aware that the plastic pipe manufacturers have been promoting locating wires with plastic pipes since on or before the 1970's, and some wire location theory is sound, in some cases locating wire systems have for various reasons not necessarily caught on or worked out very well for location in some practical applications. I see now the reputed largest manufacturer of plastic pipe in the USA (or the world, depending on source?) now also per the document at

http://jmeagle.com/pdfs/installation/MDPE_YELLOW_GAS_Installation_Guide_03-2011_web.pdf

advises that damages of plastic pipes have even been attributed to locating wires in lightning strikes, and says "The engineer must" (be the one) to make some maybe quite difficult determinations and choices per the following passage on this site:

"3.12 Pipe Locating
A standard method for locating plastic pipe requires that an electrical conductor(such as metallic wire or metallic tape) be installed with the pipe to permit location with electronic detectors.The AGA (2006 Edition) provides the following information on the use and placement of such electrical conductors: “Companies have reported thatcurrent surges (such as developed by lightning strikes) have followed the tracer causing physical damage to plastic pipe. Where practical, a separationof wire and pipe may be beneficial. However, separation may lead to difficulty in precise location of the plastic pipe. The engineer must consider the relative importance of locating the pipe versus the possibility of current surges.”

I believe the Code of Federal Regulations (CFR or ecfr) has perhaps even more vaguely addressed this issue (without even explaining why, how or who is to be responsible for the necessary wire contact minimization ) e.g. per the site

http://www.ecfr.gov/cgi-bin/text-id...t&node=49:3.1.1.1.8.7&idno=49#se49.3.192_1321

with,

"(e) Plastic pipe that is not encased must have an electrically conducting wire or other means of locating the pipe while it is underground. Tracer wire may not be wrapped around the pipe and contact with the pipe must be minimized but is not prohibited. Tracer wire or other metallic elements installed for pipe locating purposes must be resistant to corrosion damage, either by use of coated copper wire or by other means."

What is also kind of interesting about all this is I have also been told of failures, in fashion perhaps non-obvious to many, of plastics/composite pipes in lightning strikes when no locating wires were involved - maybe it can at least be concluded proximity to locating wires doesn't help!