Pressure relief valve

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On Jul 8, 1:09 pm, snipped-for-privacy@snyder.on.ca wrote:

You would have to use many of these to cover the lowest point in the system and all the high points in the various lines. I don't see it as being practical. Installing them in existing sinks, baths etc would not only be a pain, but would introduce more points for leaks in places that you don't want to leak. One of those spring loaded valves gets some debris in it, fails to shut fully, and then what?
The real question here is what's the need? Why can't the cabin be drained by just shutting a valve, opening a drain or two and turning on the faucets?

I hope they aren't being used for potable water systems, unless they are rated for them.
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On Jul 8, 1:09 pm, snipped-for-privacy@snyder.on.ca wrote:

Sprinkler System valves are not approved for potable water systems... Also there is nothing that can "automatically" drain a plumbing system with one device or valve, without also installing "automatic" valves which open at the high points on each branch of the piping to admit air and allow the pipes to drain...
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On 7/8/2012 8:29 AM, Evan wrote:

to drain the water automatically so the pipes can be easily moved.
Find an irrigation supply store and ask. Water pressure will keep it closed.
Paul
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Look up draining a trailer. Not sure how fellow did mine. Put glycol in system and hot water tank after pushing or sucking out water.
Greg
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Propylene glycol is non-toxic. It's often used for plumbing in potable water systems and is even a food additive.

I bet it's propylene glycol. Alchohol would evaporate too readily.

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On 7/8/2012 2:48 PM, Steve B wrote: ...

Not all, no...ethylene glycol is the automotive use and is; propylene glycol is a very widely used diol(+) in many places including as a potable-water anti-freeze. Almost certainly that is what your RV antifreeze is.
(+) diol - a double alcohol (a hydroxyl group attached to C)
A 'glycol' is any of a class of belonging to the alcohol family
So you're right it's an alcohol; but it's also a glycol, just not ethylene glycol and it isn't seriously toxic, fortunately. :)
If ingested the metabolism process does produce propionaldehyde, which is potentially hazardous at very high concentrations but it would be nearly impossible to reach toxic levels by consuming anything but it directly and thus is classified by US FDA as "generally recognized as safe" for use as a direct food additive.
--
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On 7/8/2012 8:15 PM, Steve B wrote: ...

"The internet" is about as nebulous as you can get--what specific piece on the internet did you find that you think disagrees with what I said? (I can assure you if it does, its wrong. :) )

That's exactly what I said. What's the problem?
The definition of a glycol is any a molecule that contains two hydroxyl groups.
An alcohol is any organic compound in which a hydroxyl functional group (OH) is bound to a carbon atom. Acyclic alcohols such as ethanol (the drinking kind) and methanol ("wood or rubbing" alcohol which is also toxic) have only a single hydroxyl group. They're alcohols, too, but they're not glycols because don't have the second hydroxyl group.
So, the glycol is a chemical term that describes a particular class of alcohols, of which ethylene and propylene are commonly used for antifreeze. They are different from each other despite both being glycols just as ethanol and methanol in one being quite toxic, the other not.
It is that 'glycol' is a general descriptive term, not specific to only one compound.
And then, I read the label on my RV antifreeze, and it is

Yes, propylene glycol is an alcohol--see above. So is ethylene glycol. _Any_ glycol is an alcohol by definition; just a specific type of an alcohol.

<http://chemistry.about.com/od/dictionariesglossaries/g/defalcohol.htm <http://chemistry.about.com/od/chemistryglossary/g/Glycol-Definition.htm
A good, basic site that is accurate...the above links are the definitions; there are links there to specifics.
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On 7/8/2012 9:46 PM, Steve B wrote:

Yeah, they'll be fine w/ the alcohol... :)
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On 7/8/2012 10:49 PM, dpb wrote: ...

Excuse me, that would be "glycol"
Sorry for thinking that somebody on usenet might actually like to learn some basic chemistry and remove the underpinnings of a misconception. What _was_ I thinking???? :(
--
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On 7/8/12 10:14 AM, Steve B wrote:

are 1". I suppose there are some made for hand move sprinkler lines also. Then there are the ones others mentioned for the lawn sprinklers. I'd be tempted to mount a cheap air compressor near the water supply. Drain the water as much as possible, then use air to push the remaining water out of the supply lines.
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I was given rv propylene glycol antifreeze, RV. I'm sure the guy knows how to fix it up for the winter. He probably has done hundreds of trailers. I never looked it up. I would want a pump or shop vac the system. The tubing goes up, down, around, and inconceivable that it would not get stuck in parts of the tubing. Purging the system with antifreeze, should get some in all tanks.
Greg
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