copper leaching in solar thermal system [RE-wrenches]

Andrew Bortz solarman2 at attbi.com
Mon Oct 21 09:59:41 PDT 2002


Todd wrote;

"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."


One thing that could explain that difference, and that I don't think has
been mentioned previously, is temperature.  As you probably know,
temperature plays a part in any chemical reaction, such as you're dealing
with.  Solar system temperature regimes would be substantially higher in
your house compared to the other.

I've seen quite a few cases, for example, where lime (and colloidal lime)
are dramatically higher in the tanks of solar thermal (SDHW) systems, than
in neighboring systems.

Anyway, I know that it's only part of the equation, but I hope it helps.

Andrew Bortz
Solar Design & Construction
solarman2 at attbi.com
Corvallis, OR

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----- 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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