I'd like to add a quality grounding rod to my house. I know from prior research,
that ground water exists from maybe 12
to 17 feet below ground, below which is hardpan. It seems that a 17 foot ground
rod would give me the best ground, but
10 feet seems to the the longest I can find. Are there longer ground rods
available? Where? Is my reasoning
How would you drive in a rod that is 17 feet long? It's a bitch
driving in a 10 footer at times. You got to get on a ladder and then
the think likes to bounce around as you sledge hammer it down.
10ft. is plenty, and in most areas, the NEC requires at least 2 rods
spaced at least 10 ft apart, then bonded together.
I am not saying you can not or should not use a longer rod, but it's
not needed and would be a pain to drive in. Actually, you could take
an 8 foot piece of galvanized pipe, put a cap on the end, drive it in,
and attach another 8 footer with a coupler. If you are lucky, the
threads on the first piece will survive. I am not sure if the NEC
approves pipe, but I have used it on the farm for electric fences and
it works as good as anything else.
Of course you could weld some rods together too....
Just weld a piece of pipe across the ends, but good luck hammering it
They make sectional ground rods; the ends are threaded (including the
pointy end), and thet have special couplers and a driving stud so you
don't bugger the threads when you pound on them.
But last time I checked, 3/4" (or larger) galvanized water pipe or RMC
is NEC approved for use as a made electrode, and can be had in 20'
lengths without needing a coupling. I would drive it using a ladder and
a T-post driver rather than a sledgehammer.
Thanks everyone. It sounds like the galvanized pipe solution will be the easiest
solution for this problem. My soil is a
fine sand below about 2 feet, so driving the rod should be no problem. I can
push a "normal" rod down 4 or more feet by
Would it be fair to assume that if I combine multiple rods that they should all
be galvanized if any one is? In other
words, I shouldn'd mix galvanized and copper plated rods?
copper is pretty much incompatible with almost all common metals except
passivated stainless steel and lead. Iron and zinc are both prone to
galvanic reactions when in contact with copper. In short - no don't
mix copper plated with other types.
Utilities buy "screw-in" ground rods that are driven in with a
gas-powered tool and have a cast screw on the end that goes in the
ground. Some of these can be "extended" to your desired 17 feet. But
these rods are not cheap (hundreds of dollars) and the tools are
Unless you are having trouble getting the low-resistance-to-ground that
the NEC requires (which might be the case if you live on the side of a
mountain for example) such measures are usually not necessary. If
you're as close to the water table as you claim then
the two code-required 8 foot/10foot rods are probably pretty good
for most purposes.
Plain old water pipe can be driven down (and extended) more easily
than ground rods to your desired 17-foot distance. Depending on
what your inspector says you will probably need the two code-compliant
(shorter) grounding electrodes too.
The "low-resistance-to-ground that the NEC requires" for ground rods is
25 ohms, which is a joke. I would rather use a 16 foot ground rod than
2 8' rods because it would get into other soil types and get closer to
wet soil. Also, I presume the top of a ground rod is ineffective in the
winter in the frost belt.
I think (not sure) rods with threaded ends, as described by Bob, used to
be around - havn't looked recently.
Also think (not sure) I have seen attachments for some of the larger
hammer drills that are for driving ground rods.
A threaded 3/4" grounding rod is around $25 for 10 feet, including
the pointed end. Couplings are around $8. Not as beefy as what the
utilities use, but how many amps do you plan to dump down a household
firstname.lastname@example.org is Joshua Putnam
quality grounding rod?
I know of no study that has found that getting a ground rod into the water
table is worth the effort. Sure would be hard for us folks in the SW
Placement of the "supplemental ground rod" should be outside the sphere of
the primary grounding system. Amec makes a meter that can measure
ohms/volts to ground with out interruption.
http://www.giscogeo.com/pages/grsae371.html My personal favorite.
I measured my last house and found that the installed ufer ground was less
than 10 ohms. Not much reason to spend the effort in setting another ground
in that situation. That was done on a dry July morning.
From the picture and the text that device is only measuring current. Its
somehow calculating resistance based on that - I cant imagine it being
anywhere's near accurate. If it were that simple you could use your clampon
ammeter and a table.
How do you suppose ohmmeters work? The caculation is done by the
mechanism in mechanical meters, but all they do is measure amperage,
which they do by measuring voltage drop. Everything is calculated
from voltage drop, mechanically or electronically.
If it were that simple you could use your clampon
If your clampon is accurate.
Remove NOPSAM to email me. Please let
me know if you have posted also.
Yeah, but who has all these meters and stuff, Aside from the electric
company and some of the large electricians?
Unless you install ground rods on a daily basis, it's cheaper to just
install the 2 rods specified in the NEC, and be done with it. You can
never "over ground". In fact 3 or 4 rods are even better. On my
garage, there are 2 rods, plus I ran a wire over to one of the pieces
of large angle iron buried in the ground from an old steel windmill.
The windmill is long gone, but these steel legs stuck out of the
ground and constantly tripped me. I finally put my stick welder on
full power and burned off 3 of them under the surface of the ground.
I dont know how deep they go, but my tractor loader would not budge
them. The 4th one I left as a ground., and placed a t-post next to it
so I dont trip over it.
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