Expert: Sharon McCarthy - 7/8/2009

Question
The first summer in my home has been a nightmare! I have
found an unbelievable amount of molehills along a creek in
my backyard, accompanied by another huge molehill in my yard
with countless burrowed holes!
My question is, besides destroying my soil and yard, can
moles damage pipes? I am having plumbing problems.

Answer
Diana,

  How awful!! I've heard they are very difficult to get rid of. I considered passing on this question because I honestly don't know if moles could actually chew through sewer pipe. I imagine this is what you're referring to about "plumbing problems". Probably not waterlines, I doubt they could get into copper, PVC or galvanized.

  If your problems are the sewer line, it probably depends on what kind of material your sewer pipe is. Like do you know if it is ABS plastic [black plastic, very heavy-walled, all parts glued together] or an older type of sewer pipe, like "Orangeburg" or clay pipe.

  Orangeburg pipe is named after the town in New York [my understanding] where it was manufactured. It's a composite material, like a very heavy tar paper, and the couplings that connect the pipes are just pressed together, not glued.

  When I started plumbing 26 years ago, here in Arizona, I saved up my money and bought a really good roto-rooter machine because so many of my calls were plumbing back-ups. Many houses in the two little towns where I work are over 40 years old, and most of the sewerlines to the septic tanks in those older homes were plumbed with Orangeburg.

  This material is not very durable. I could swing a hammer and go right through it. Anywhere there is a coupling, water will eventually begin to seep out. Then roots find the water and work their way into the pipe. This then weakens those pipe ends even more. I suppose it's possible that moles could do some damage at that point.

 Clay pipe is sturdier, but it can leak the same way, at joints, and get infested with roots. If your sewer lines are either of those materials, and you are having back-ups, the best thing to do is have the whole line replaced with ABS.

  I've dug up many many yards of old pipe by hand and replaced it with ABS. Usually with a septic system the pipes aren't very deep. If you are on a municipal sewer, the pipes may be deeper.

  I can't help you with the mole problem, wish I could! We have pack-rat problems in the desert, very very persistent little critters! And they love to chew insulation on wires. Their nests are quite colorful! Good luck with your battle! Sharon