Re: Emergency Water Turn-Off?

["Robert Green" <ROBERT_GREEN1963@xxxxxxxxx>]

"Matt" <mattmorgan64@xxxxxxx> wrote in message

> I do know that the cost of water heaters recently went up about 30%
> because the gov't mandated that the pilot and flame be enclosed in the
> hopes of preventing an explosion in the presense of flammable vapors.

Yeah, but that's probably a good thing.  It's likely to be one of the
primary combustion triggers in a serious gas leak.  Unlike dryers and
ranges, the water heater is likely to follow a pattern of waiting an hour or
two, even in an empty house and then lighting up for a few seconds.
Probably couldn't design a more efficient way to allow gas to collect in a
basement and then ignite it!  :-)

> But I don't know of any safeties on a water heater for an out of
> water condition. Seems like to me the thermostat is going to call
> for heat in an empty situation, and the burner will simply
> continue to run; I suppose until someone notices or the bottom
> of the WH burns up, what follows that I don't know.

I've found one site that says this about electric WH's:

|Remember that with an electric water heater, you must turn the |power off!
Even a partial drain down may expose the upper |heating element to the air
and permanently damage it!

http://www.naturalhandyman.com/iip/infwaterheater/infdrainwh.shtm

I found some really interesting information at another website that counters
everything I had heard up until now about water heaters:

http://www.waterheaterrescue.com/pages/WHRpages/English/hot-water-heater-saf
ety.html

|Temperature control. On commercial tanks, they're set in
|degrees, but on residential tanks, expect warm, hot, very hot, or
|something like that. There is so much variation on what those
|settings mean, heater to heater, that all we can tell you is that the
|right temperature is at least 130 degrees at the tap, which you can
|test with a meat or candy thermometer.

|Why 130? Well, at 120, legionella bacteria that cause
|Legionnaire's disease can grow. Then when you take a shower, you
|catch it by inhaling the mist. Anything above 130 vastly increases
|scalding risk, energy use and sediment buildup. Truth is, 130 is a
|compromise temperature. You can be scalded there, too, if you
|spend long enough under the water, but it is sufficiently hot that
|you'll probably draw back, but not so hot that you'll JUMP back.
|Most bathing injuries are not from burns, but falls.

Well, that's news to me.  I am going to jack that temperature up the next
time I go to the basement!

> On the other hand, I'd like to believe that there is either some sort
> of safety built in to prevent this,  or a logical reason why it isn't
> an issue. I don't recall of hearing any horror stories of water
> heater burn up;

Well, I haven't seen any sites that detail any "empty tank" safeties but if
they are enclosing the combustion chamber and mandating earthquake strapping
in CA, then SOMETHING's got to be in there to prevent a burnout.  I hope.

> but I have seen videos of water heaters shooting off like
> rockets, before the PRV was standard issue; blowing through
> 2 or 3 floors and finally the roof, continuing their journey into
> the sky......

That's why they have so many stickers attached to them.  In case they reach
escape velocity and travel to another solar system.  We used to have a few
fire safety engineers hanging around that could give us the real scoop on WH
safety.

--
Bobby G.