copper leaching in solar thermal system [RE-wrenches]

[James Lamb, Middle Fork Engineering]

Todd & Matt
Natural gas and Oil pipes are insulated from the ground. They have a coating
on them. If there is a break in the coating corrosion will occur at this
location because of the difference in potential. An anode or an voltage
potential (solar collector or grid) is applied to the pipe to prevent
corrosion just in case there is a break in the insulation. 
JIM LAMB
Middefork Engineering 

-----Original Message-----
From: matthew tritt [mailto:solarone at charter.net]
Sent: Sunday, October 20, 2002 7:38 PM
To: RE-wrenches at topica.com
Subject: Re: copper leaching in solar thermal system [RE-wrenches]


Todd,

Are the buried pipes insulated/isolated from the earth, and have you tried
putting an Ohm meter on the pipes and the earth? There's got to be some kind
of difference in potential going on. I still wonder about the grounding
question. It sounds far-fetched, but you might also check for measurable
voltage between the pipes and ground.

Plenty weird.

Matt
----- Original Message -----
From: "Todd Cory, Mt. Shasta Energy Services" <toddcory at finestplanet.com>
To: <RE-wrenches at topica.com>
Sent: Sunday, October 20, 2002 4:25 PM
Subject: Re: copper leaching in solar thermal system [RE-wrenches]


> Yes, dielectric unions at the water heater, the only place where
dissimilar
> metals meet. The rest of the loop is copper, stainless and brass (all
> compatible). The water has very low total dissolved solids and is not
acidic
> (anodes last forever). There are 2 homes on this well and only the home
with
> the solar thermal is making the shower green, so I know that is the cause,
> for some unknown reason.
>
> I wonder how long the water can contain enough copper to make the shower
> green before the potable side of the loop to the heat exchanger is so thin
> it starts to leak. The glycol half loop of the loop is buried to another
> building where the collectors are located. I have seen PV panels used to
> apply power to buried natural gas pipes to prevent some kind of corrosion.
I
> am not sure why they do that, nor if this might be more of an electrical
> (anode/cathode) situation because the glycol part of the loop is buried to
> the panels located on a metal roof on another building.
>
> Since the plumbing was done right and the water quality is not the problem
> that leaves my question about different electrical potentials on one end
of
> the glycol loop and the other end of the potable loop. Does anyone have
any
> ideas how electrical characteristics with burying copper pipes or having
> them span possible different electrical potentials might cause them to
> corrode? You would think if they are copper (a great conductor) there
could
> be no dissimilar electrical potential?? This is a mystery to me, but I
know
> something is wrong because the pipes are leaching their copper into the
> water.
>
> Todd
>
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