GSHP (Geothermal) and tree roots?

DavidRNovember 25, 2010

An older friend of ours has a relatively new home (~11 years old) with a Water Furnace GSHP. She planted a cherry tree behind the house shortly after moving in. Now she's talking about having it removed, because as it grows she's becoming concerned that its roots might interfere with or damage the HP's loop.

She has no idea where the loop is located. I suspect it's nowhere near where the tree is, and is probably deep enough (seems to be plumbed through the cellar floor, a good 10' below grade) that no landscaping is likely to damage it. But I'm far from being an expert.

Regardless of where the loop may actually be buried, can anyone say whether this is a legitimate concern? Has anyone seen any examples of GSHP loops being affected by tree roots? I'd like to be able to put her mind at ease, but don't want to do so if there's a good reason for her to be concerned.


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Does she know if vertical wells were used, or a horizontal loop? (unless the piece of land is quite large, it is most likely vertical wells)

Vertical wells for GSHPs are dug quite deep--around 150 feet or so-- and then loop pipe is typically suspended in the well with something similar to concrete.

Is the tree close to where the loops are located and connect to the heat pump or basement connections?

    Bookmark   November 26, 2010 at 9:28AM
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This might seem like I have a screw loose of a whole handful but here goes. There is a technique called 'Witching' that will allow you to follow the pipes outside. There are probably some demonstrations on youtube. I found a pretty good one. You can make your own rods out of coat hangers and they will cross completely over each other when you get on top of the lines. If you step back slowly after the rods have both crossed side by side in front of you and marking that spot you will notice they will slowly open back to pointing straight out. This distance is an 'Idea' of depth. Sometimes it is pretty accurate if you do it multiple times from both sides and average your measurements.

We use these methods at work quite often if another utilities locates seem to be off the mark when trying to dig across them. It does work but some people think your nuttier than squirrel poop when they see you out walking around with two metal sticks.

Here is a link that might be useful: 'Witching'

    Bookmark   November 27, 2010 at 1:01PM
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I'll see what I can find out about how the system is configured. Part of the problem is that she doesn't have a clue where the loop is located.

The lot is pretty good sized - I think a couple of acres - but it's almost all setback. The lot drops off maybe 15-20 feet behind the house into a ravine, so I doubt that the installers would have tried to use that area.

But it sounds like it might not be a problem.

If it's a horizontal loop, it would almost have to be in front of the house - and the tree she's concerned about is just behind the house. And if it's in vertical wells, it seems unlikely to be an issue.

Another thought - she should still have the name of the general contractor. Maybe he would know who installed the GSHP. Seems to me the best course would be to ask him.

    Bookmark   November 27, 2010 at 4:04PM
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IâÂÂd leave the tree.

This should not be a problem at all; the High Density Poly Ethylene plastic pipe is extremely tough!


    Bookmark   November 27, 2010 at 7:46PM
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Unless it's bad luck and the tree root just happens to push on an underground line, tree roots won't 'seek out' water lines contrary to myth, unless they're leaking.

Almost all the loops I see are vertical wells. The other clue is which direction the lines travel out through the basement - they're likely to take the shortest route to the loops, ie if they disappear into the floor near the front of the house, I'd bet they're there.

I do work at a new planned community that's exclusively geothermal and I haven't seen any landscaping rules in that sense, although they don't seem to plant anything big in the front yard and the loops/wells always seem to be in the front.

I should think the tree's ok.

    Bookmark   November 30, 2010 at 3:05PM
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There is no reason to think tree roots will damage the piping. If it's not leaking the roots have no reason to think (do roots think?) there is water inside the pipe and will just go around it.
Tell her to find something else to worry about.

    Bookmark   December 1, 2010 at 8:17PM
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