My HVAC contractor installed two linesets, one from my basement apartment, one from the main unit, both going to the roof where the air condensers are. The problem is, he did it over several days and I have a suspicion that he messed up which pipe/wire goes where, i.e. that he mixed them. He claims that he marked it along the way but I am skeptical. Both linesets (fat and skinny flex copper, power supply, and thermostat) enter the roof through lead cones. It is not possible to trace the pipes along the way because most of their way is now blocked to sight. Only the linesets have been installed thus far, so there is no air handler/condensers installed on their end, so the pipes are empty.

Is it possible to use a small amount of current (from a battery?) and send it on one end of the pipe while checking it with a multimeter or some voltage detector on the other end? If yes, how should I rig up such a contraption? Can I just wire the battery onto the pipe?

  • Have you tried tapping the end of the pipe with something like the blade of a screwdriver? At the other end hold your ear to each pipe. Should be louder on the one being tapped if they don't connect. Since they're not connected yet.. would it be safe to pour some water down into one and see where it comes out? Or would that potentially cause issues with the refrigerant later? – OrganicLawnDIY Mar 3 '14 at 5:50

Put an earbud from your cell phone or iPod in one of the tubes. Crank up some music. Put your ear to the other end. You will absolutely be able to tell the difference between the one with the earbud in it and the other three.


They are pipes, even though it will be frowned upon by HVAC personel, get an air compressor and hook up to the pipe and see which one produces air at the other end. In my opinion it is better to endure a little air born moisture in the pipe, than have them crossed up. This may be my naivety showing, but the lines are purged before pressurizing with the refrigerant.

The wires are no problem, they will sort that out on their connecting. A multimeter or other specialized testing tool that they have can determine what goes where. Please pardon my highly advanced technical vocabulary on the name for the equipment.

  • A Cat-5 tone tracer might work. – Mazura Apr 22 '15 at 20:08

Simply use air blower from one end and check air is coming out in another end. Recently I have used this method for copper pipe checking. If connections are made then use only and only one method that's to check continuity with clamp meter. Hope you get the answer.


If pipes are touching at any point it won't work. If they aren't touching, I would use an extension cord connected to one end of pipe (tape a piece of wire to the pipe) and a ohm meter in between pipe and extension cord at other end. Test for resistance and you don't have to use any external electrical source.

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    If they weren't touching i would use an extension cord connected to one end of pipe(stick piece of wire into socket) and a ohm meter in between pipe and extension cord at other. Test for resistance – Justin K Mar 3 '14 at 1:51


I assume you are in the US, where different rules may apply. In the UK, all copper piping would be electrically bonded together (equipotential bonding) for safety. This can occur at multiple places in the pipe run. It's also possible (though unusual) to use plastic push-fit joints on copper pipe. This means you can't reliably use simple electrical means to check copper piping continuity.


If the pipes are intended to carry water (working fluid for an AC unit), maybe you could pour some in at the top and see which carefully positioned bucket at the bottom starts to fill.


If you can light up a bulb with a battery, you should be able to use this approach (assuming the two runs of pipe never touch). Attach one side of a low voltage battery (e.g., 1.5, 6, or 9 v) at the bottom and string a long wire up to the top of the two pipes, and use a little light bulb or a VOM to see which pipe is energized.

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