I was advised to also replace the vacuum relief valve when I recently
had to replace our home's (leaking) water heater. Since the part was
cheap enough and I'd never thought to replace it in the 23 years (and
two previous water heater replacements by me.) since its original
installation, I went ahead and bought one.

Then I started wondering just what conditions would cause enough
negative pressure to collapse a water heater tank.

*******
The description of Watts' vacuum relief valve reads:

Series N36 Watts Water Service Vacuum Relief Valves are used in water
heater/tank applications to automatically allow air to enter into the
piping system to prevent vacuum conditions that could siphon the water
from the system and damage water heater/tank equipment.
*******

Since our home is at the crest of hill, I suppose that if the city
pumping system went bad, or a water main below us burst there could be a
long enough column of water "hanging down" to pull up to one atmosphere
of vacuum in our home's supply, which is probably more than enough to
collapse a water heater tank.

A plumber I asked said that a fire engine pumping out of a nearby
hydrant could also create a negative pressure in the main.

Are those the expected kind of things a vacuum relief valve protects
against?

Thanks guys, and Happy New Year,

Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.

On Dec 29, 1:04*pm, Jeff Wisnia wrote:
I was advised to also replace the vacuum relief valve when I recently
had to replace our home's (leaking) water heater. Since the part was
cheap enough and I'd never thought to replace it in the 23 years (and
two previous water heater replacements by me.) since its original
installation, I went ahead and bought one.

Then I started wondering just what conditions would cause enough
negative pressure to collapse a water heater tank.

*******
The description of Watts' vacuum relief valve reads:

Series N36 Watts Water Service Vacuum Relief Valves are used in water
heater/tank applications to automatically allow air to enter into the
piping system to prevent vacuum conditions that could siphon the water
from the system and damage water heater/tank equipment.
*******

Since our home is at the crest of hill, I suppose that if the city
pumping system went bad, or a water main below us burst there could be a
long enough column of water "hanging down" to pull up to one atmosphere
of vacuum in our home's supply, which is probably more than enough to
collapse a water heater tank.

A plumber I asked said that a fire engine pumping out of a nearby
hydrant could also create a negative pressure in the main.

Are those the expected kind of things a vacuum relief valve protects
against?

Thanks guys, and Happy New Year,

Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.


I would guess that the main concern is not siphoning action collapsing
the tank, but it taking enough of the water out so that either the
electric elements then burn out or steam is generated with a gas unit,
exploding the tank. Of course the TPR valve is there to hopefully
prevent the latter.

Here in NJ, I've never seen one used, even in new construction. So,
apparently here they are not required by code. The first time I ever
even saw one on a water heater was on a recent episode of This Old
House, when they were removing a water heater. All in all, unless
I'm missing something, I don't see the need.

wrote:

On Dec 29, 1:04 pm, Jeff Wisnia wrote:

I was advised to also replace the vacuum relief valve when I recently
had to replace our home's (leaking) water heater. Since the part was
cheap enough and I'd never thought to replace it in the 23 years (and
two previous water heater replacements by me.) since its original
installation, I went ahead and bought one.

Then I started wondering just what conditions would cause enough
negative pressure to collapse a water heater tank.

*******
The description of Watts' vacuum relief valve reads:

Series N36 Watts Water Service Vacuum Relief Valves are used in water
heater/tank applications to automatically allow air to enter into the
piping system to prevent vacuum conditions that could siphon the water
from the system and damage water heater/tank equipment.
*******

Since our home is at the crest of hill, I suppose that if the city
pumping system went bad, or a water main below us burst there could be a
long enough column of water "hanging down" to pull up to one atmosphere
of vacuum in our home's supply, which is probably more than enough to
collapse a water heater tank.

A plumber I asked said that a fire engine pumping out of a nearby
hydrant could also create a negative pressure in the main.

Are those the expected kind of things a vacuum relief valve protects
against?

Thanks guys, and Happy New Year,

Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.



I would guess that the main concern is not siphoning action collapsing
the tank, but it taking enough of the water out so that either the
electric elements then burn out or steam is generated with a gas unit,
exploding the tank. Of course the TPR valve is there to hopefully
prevent the latter.

I hadn't thought of that "overheating" angle, thanks.

I suppose it would require someone to open a hot water faucet and leave
it open long enough for the tank to have enough of its contents sucked
out through the dip tube to cause that kind of problem. Since there's no
telling what sorts of things folks might decide to do, your point sounds
valid to me.

It was also mentioned to me by my plumber aquaintance that present codes
here in Red Sox Nation require power disconnect switches adjacent to new
electric water heater installations for the same reason they've been
used for a long time near outside AC units. They can prevent repair
folks from getting zapped or whacked when someone else decides to flip a
panel breaker back on while they're messing around inside the equipment.

I wonder what's next?

Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.


Here in NJ, I've never seen one used, even in new construction. So,
apparently here they are not required by code. The first time I ever
even saw one on a water heater was on a recent episode of This Old
House, when they were removing a water heater. All in all, unless
I'm missing something, I don't see the need.

It was also mentioned to me by my plumber aquaintance that present codes
here in Red Sox Nation require power disconnect switches adjacent to new
electric water heater installations for the same reason they've been
used for a long time near outside AC units. They can prevent repair
folks from getting zapped or whacked when someone else decides to flip a
panel breaker back on while they're messing around inside the equipment.

I wonder what's next?

Jeff
--
Jeffry Wisnia

All new vehicles will come with no tamper GPS receivers. if tye GPS
breaks the vehicle doesnt run.

it checks the speed limit on the road you are on and acting like a
govenor prevents speeding.

in a chase situation where police are chasing a vehicle they send out
a signal, all close by vehicles drop to 5 MPH limit

national tracking of all people begins, technically it already has
with cell phones.

every citizen gets a new national ID card, in exchange for DNA sample,
picture and fingerprints, plus retinal scan.

great for searching out bad guys. making credit card purachase? just
one card will work for any person, with fingerprint scan and id number
charge gets applied to your account. cash is becoming obsolete for
better tracking.

dont laugh its all for our safety

On Mon, 29 Dec 2008 10:10:21 -0800 (PST), wrote:

I would guess that the main concern is not siphoning action collapsing
the tank, but it taking enough of the water out so that either the
electric elements then burn out

If siphoning would suck enough water out to uncover an electric
heating element, having a vacuum relief valve wouldn't help. It
doesn't just make the vacuum disappear. It gets rid of it by allowing
air to enter.

or steam is generated with a gas unit,
exploding the tank.

I don't know about gas, except the kind we can't discuss politely.

Of course the TPR valve is there to hopefully
prevent the latter.

Here in NJ, I've never seen one used, even in new construction. So,
apparently here they are not required by code. The first time I ever
even saw one on a water heater was on a recent episode of This Old
House, when they were removing a water heater. All in all, unless
I'm missing something, I don't see the need.

mm wrote:

On Mon, 29 Dec 2008 10:10:21 -0800 (PST), wrote:


I would guess that the main concern is not siphoning action collapsing
the tank, but it taking enough of the water out so that either the
electric elements then burn out


If siphoning would suck enough water out to uncover an electric
heating element, having a vacuum relief valve wouldn't help. It
doesn't just make the vacuum disappear. It gets rid of it by allowing
air to enter.

I'll have to take issue with that statement, mm.

If something going wrong with the home's water main supply causes a
negative pressure at the heater's cold water inlet and a hot water
faucet is opened, water could get sucked out of the tank (and the hot
water pipes coming from the open faucet) through the heater's dip tube,
lowering the level in the tank down to the bottom of the dip tube, which
will certainly expose the element(s).

A vacuum relief valve teed onto the heater's inlet pipe "breaks" the
vacuum right there so water won't get sucked out of the tank.

Capice, mm?

Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.98*10^14 fathoms per fortnight.


or steam is generated with a gas unit,
exploding the tank.


I don't know about gas, except the kind we can't discuss politely.


Of course the TPR valve is there to hopefully
prevent the latter.

Here in NJ, I've never seen one used, even in new construction. So,
apparently here they are not required by code. The first time I ever
even saw one on a water heater was on a recent episode of This Old
House, when they were removing a water heater. All in all, unless
I'm missing something, I don't see the need.

mm wrote:
On Mon, 29 Dec 2008 10:10:21 -0800 (PST), wrote:


I would guess that the main concern is not siphoning action collapsing
the tank, but it taking enough of the water out so that either the
electric elements then burn out


If siphoning would suck enough water out to uncover an electric
heating element, having a vacuum relief valve wouldn't help. It
doesn't just make the vacuum disappear. It gets rid of it by allowing
air to enter.


or steam is generated with a gas unit,
exploding the tank.


I don't know about gas, except the kind we can't discuss politely.


Of course the TPR valve is there to hopefully
prevent the latter.

Here in NJ, I've never seen one used, even in new construction. So,
apparently here they are not required by code. The first time I ever
even saw one on a water heater was on a recent episode of This Old
House, when they were removing a water heater. All in all, unless
I'm missing something, I don't see the need.




I had someone tell me today that some heater's dip tubes have a small
hole near their top to prevent sucking down the water level in the tank
through the inlet fitting. That could prevent the burnout problem that
trader4 brought up, though it wouldn't stop a collapse of the tank under
the "wrong" conditions.

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.

On Dec 29, 4:25*pm, " wrote:
dont laugh its all for our safety

Ha ha ha.

Too bad it will take two people for every one of us to effectively
monitor our activities to the extent that the "big brother is
watching" conspiracy theorists often spout off about.

Soooo, who is paying the salaries of the 600 million "big brothers"
watching the 300 million of us? Where are they hiding 600 million
government employees?

On Tue, 30 Dec 2008 00:16:49 -0500, Jeff Wisnia
wrote:

mm wrote:

On Mon, 29 Dec 2008 10:10:21 -0800 (PST), wrote:


I would guess that the main concern is not siphoning action collapsing
the tank, but it taking enough of the water out so that either the
electric elements then burn out


If siphoning would suck enough water out to uncover an electric
heating element, having a vacuum relief valve wouldn't help. It
doesn't just make the vacuum disappear. It gets rid of it by allowing
air to enter.

I'll have to take issue with that statement, mm.

If something going wrong with the home's water main supply causes a
negative pressure at the heater's cold water inlet and a hot water
faucet is opened, water could get sucked out of the tank (and the hot
water pipes coming from the open faucet) through the heater's dip tube,
lowering the level in the tank down to the bottom of the dip tube, which
will certainly expose the element(s).

A vacuum relief valve teed onto the heater's inlet pipe "breaks" the
vacuum right there so water won't get sucked out of the tank.

Capice, mm?

Jeff

I get it. Thanks.

On Dec 30, 1:39�pm, wrote:
On Dec 29, 4:25�pm, " wrote:

dont laugh its all for our safety

Ha ha ha.

Too bad it will take two people for every one of us to effectively
monitor our activities to the extent that the "big brother is
watching" conspiracy theorists often spout off about.

Soooo, who is paying the salaries of the 600 million "big brothers"
watching the 300 million of us? Where are they hiding 600 million
government employees?

Artifical intelligence, computers are already listening in for key
words phrases etc. ones of interest get reviewed by humans.

it is true that every country tried this in the past failed because of
costs and inhibiting creativity by the population.

a national DNA data base will help find murders rapists etc.

no I am NOT in favor of big brother! just reporting on whats coming