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Propylene Glycol Heat Transfer Fluid - Page 6

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Posted by DJ on May 29, 2005, 2:41 pm

daestrom wrote:

The old chestnut of "Nothing is foolproof because fools are so
ingenious" ;-). At some point, you gotta sit back, and say, "well, due
dilligence and all that, but this is just getting silly..."
Back in my chem plant days, double-walls were plumbed and sent to
collection tanks in case they leaked, from either side. Which worked
nicely. Others had sensors that shut off pumps and closed isolation
solenoids if a leak was detected. Sure, that works, too. But it
hearkens back to the old story of the debate about whether to give
everyone a bullet proof vest, or to just take the bullets out of the
gun ;-). SDHW just ain't that complicated, and I don't think it's worth
that degree of agravation and worry.

Since there is now downside to taking the bullets out of the gun (the
automotive glycol out of the system), it seems a no-brainer to me.

And had a thought, really, about that "second or third owner" scenario,
which is valid. If you were buying a house with an SDHW system on it,
that's tacking on several thousand dollars onto the price. If it were
me, I'd get it checked out before I agreed that it was worth that. And
that would include checking, and probably flushing, the glycol system.
People who build these things themselves usually keep an eye on them.
But alot of my recent maintenance jobs on systems other people have
installed tend to be of the "What do you mean we have to change the
glycol sometimes?" on systems that have been in the sun for twenty
I was doing an eighties vintage one the other day; system worked well;
but it had outlived the roof under it, so it was a
uninstall/re-roof/reinstall. Drainback design too. Sweet and easy.
Glycol was last looked at in '89. But even then, it was replaced with

Now I'm picturing your smug self hitting "send" and THEN the meteor
hitting ;-).

Ever seen the flick, "Final Destination"? ;-).


Posted by daestrom on May 30, 2005, 2:03 am

Yes, well we *could* get extreme.  It depends on lot on the consequences of
a failure.  Mix the wrong kinds of chemicals and perhaps you have a big
*BOOM*.  Or start releasing cyanide gas or some such.

But going from one barrier preventing poisoning a household, to two barriers
doesn't seem like it's *that* extreme.  At least not to me. But opinions
vary I guess.  Some jurisdictions plumbing code may differ.

P.S.  Where *IS* that meteor, it's now several hours overdue.....:-)

Posted by DJ on May 30, 2005, 12:06 pm

daestrom wrote:

Exactly. And with proper SDHW systems, one day, worst case, you're in
the shower, and you get a craving for Dairy Queen ice cream (60%
prop.gly) for some reason ;-).

Oh, absolutely. Or you destroy thousands of dollars of chemicals. It's
exactly that: prevention comparable to the cost of failure.

You'll easily double the size and the price of the heat exchanger,
maybe more. For a multi-million dollar chem plant, operating costs. For
a few grand in a home SDHW system... needless expense.

In my opinion, of course ;-).


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