Ok, I have a cabin in the country. Because the propane WH is getting
close to being old, when I'm not going to be there for a week or so I
turn the water inlet valve off and the thermostat to pilot. That way
if it leaks, the water spilled will be limited to 40 gallons.
Anyway, when I turn the water valve back on after a week or two, there
is a good amount of air in the tank and hot water lines. There is no
water around the heater. There is no indication of rust on the tank
burner or tank bottom. I crawled under the cabin and there is no
water spotting on the subfloor, nor water on the vapor barrior.
So I'm puzzled. Where is this air in the tank coming from? I'm
talking about air/water spewing for up to a minute. First thought was
a leak and second thought was volume contraction due to cooling. But
that much???

Bob

Bob wrote:
Ok, I have a cabin in the country. Because the propane WH is getting
close to being old, when I'm not going to be there for a week or so I
turn the water inlet valve off and the thermostat to pilot. That way
if it leaks, the water spilled will be limited to 40 gallons.
Anyway, when I turn the water valve back on after a week or two, there
is a good amount of air in the tank and hot water lines. There is no
water around the heater. There is no indication of rust on the tank
burner or tank bottom. I crawled under the cabin and there is no
water spotting on the subfloor, nor water on the vapor barrior.
So I'm puzzled. Where is this air in the tank coming from? I'm
talking about air/water spewing for up to a minute. First thought was
a leak and second thought was volume contraction due to cooling. But
that much???

Bob

Valve is not closing tightly. Air gets in thru faucets, etc..

On Feb 14, 12:08 pm, "Bob" wrote:
Ok, I have a cabin in the country. Because the propane WH is getting
close to being old, when I'm not going to be there for a week or so I
turn the water inlet valve off and the thermostat to pilot. That way
if it leaks, the water spilled will be limited to 40 gallons.
Anyway, when I turn the water valve back on after a week or two, there
is a good amount of air in the tank and hot water lines. There is no
water around the heater. There is no indication of rust on the tank
burner or tank bottom. I crawled under the cabin and there is no
water spotting on the subfloor, nor water on the vapor barrior.
So I'm puzzled. Where is this air in the tank coming from? I'm
talking about air/water spewing for up to a minute. First thought was
a leak and second thought was volume contraction due to cooling. But
that much???

Bob

Cooling water heaters suck
It's probably "sucking air" when it's off.
For a demonstration try this fun experiment, get an empty gallon
plastic milk jug and put a 1/4 cup of water in it, now stick it in
the microwave (with the lid OFF) just long enough to get the water
good and hot, now take it out and screw the lid on and let it cool off
(you can set it in the fridge if you want fast results)....see what
happens to the jug??
Cool huh?
When your water heater cools it does the same thing...only it is
stronger than a plastic jug.

George

On Feb 14, 1:04 pm, "George" wrote:
On Feb 14, 12:08 pm, "Bob" wrote:

Ok, I have a cabin in the country. Because the propane WH is getting
close to being old, when I'm not going to be there for a week or so I
turn the water inlet valve off and the thermostat to pilot. That way
if it leaks, the water spilled will be limited to 40 gallons.
Anyway, when I turn the water valve back on after a week or two, there
is a good amount of air in the tank and hot water lines. There is no
water around the heater. There is no indication of rust on the tank
burner or tank bottom. I crawled under the cabin and there is no
water spotting on the subfloor, nor water on the vapor barrior.
So I'm puzzled. Where is this air in the tank coming from? I'm
talking about air/water spewing for up to a minute. First thought was
a leak and second thought was volume contraction due to cooling. But
that much???

Bob

Cooling water heaters suck
It's probably "sucking air" when it's off.
For a demonstration try this fun experiment, get an empty gallon
plastic milk jug and put a 1/4 cup of water in it, now stick it in
the microwave (with the lid OFF) just long enough to get the water
good and hot, now take it out and screw the lid on and let it cool off
(you can set it in the fridge if you want fast results)....see what
happens to the jug??
Cool huh?
When your water heater cools it does the same thing...only it is
stronger than a plastic jug.

George

Ok, I can buy that. But with the faucets closed, where's the air
coming from, the pressure relief valve backflow? And where is the
water that is replaced by air going?

Bob wrote:
On Feb 14, 1:04 pm, "George" wrote:
On Feb 14, 12:08 pm, "Bob" wrote:

Ok, I have a cabin in the country. Because the propane WH is
getting close to being old, when I'm not going to be there for a
week or so I turn the water inlet valve off and the thermostat to
pilot. That way if it leaks, the water spilled will be limited to
40 gallons.
Anyway, when I turn the water valve back on after a week or two,
there is a good amount of air in the tank and hot water lines.
There is no water around the heater. There is no indication of
rust on the tank burner or tank bottom. I crawled under the cabin
and there is no water spotting on the subfloor, nor water on the
vapor barrior.
So I'm puzzled. Where is this air in the tank coming from? I'm
talking about air/water spewing for up to a minute. First thought
was a leak and second thought was volume contraction due to
cooling. But that much???

Bob

Cooling water heaters suck
It's probably "sucking air" when it's off.
For a demonstration try this fun experiment, get an empty gallon
plastic milk jug and put a 1/4 cup of water in it, now stick it in
the microwave (with the lid OFF) just long enough to get the water
good and hot, now take it out and screw the lid on and let it cool
off (you can set it in the fridge if you want fast results)....see
what happens to the jug??
Cool huh?
When your water heater cools it does the same thing...only it is
stronger than a plastic jug.

George

Ok, I can buy that. But with the faucets closed, where's the air
coming from, the pressure relief valve backflow? And where is the
water that is replaced by air going?

I would guess either the PR valve or the air could be coming from the
water. Water does absorb air. How much air depends on the temperature and
pressure. Have you not noticed that sometimes when you fill a glass with
water (during the winter) it is milky looking. That is air that was in the
water. The time of year and the change in temperature of the water may be
forcing dissolved gasses.

--
Joseph Meehan

Dia 's Muire duit

On 14 Feb 2007 09:08:56 -0800, "Bob" wrote:

Ok, I have a cabin in the country. Because the propane WH is getting
close to being old, when I'm not going to be there for a week or so I
turn the water inlet valve off and the thermostat to pilot. That way
if it leaks, the water spilled will be limited to 40 gallons.
Anyway, when I turn the water valve back on after a week or two, there
is a good amount of air in the tank and hot water lines. There is no
water around the heater. There is no indication of rust on the tank
burner or tank bottom. I crawled under the cabin and there is no
water spotting on the subfloor, nor water on the vapor barrior.
So I'm puzzled. Where is this air in the tank coming from? I'm
talking about air/water spewing for up to a minute. First thought was
a leak and second thought was volume contraction due to cooling. But
that much???

I have your water. You can have it back for 3000 dollars in small
bills.

Bob

George wrote:


For a demonstration try this fun experiment, get an empty gallon
plastic milk jug and put a 1/4 cup of water in it, now stick it in
the microwave (with the lid OFF) just long enough to get the water
good and hot, now take it out and screw the lid on and let it cool off
(you can set it in the fridge if you want fast results)....see what
happens to the jug??
Cool huh?
When your water heater cools it does the same thing...only it is
stronger than a plastic jug.

George


Try your experiment with a full jug(water heater). The results will be
different.

Rob

Bob wrote:

Ok, I can buy that. But with the faucets closed, where's the air
coming from, the pressure relief valve backflow? And where is the
water that is replaced by air going?

Faucets are optimized to prevent stuff from going in one direction, not the
other.

The suckage may be much greater than normal water pressure anyway.

On Feb 14, 2:11 pm, "Joseph Meehan"
wrote:

I would guess either the PR valve or the air could be coming from the
water. Water does absorb air. How much air depends on the temperature and
pressure. Have you not noticed that sometimes when you fill a glass with
water (during the winter) it is milky looking. That is air that was in the
water. The time of year and the change in temperature of the water may be
forcing dissolved gasses.

A good possibility. First water flow is somewhat opaque, then clears.
I never thought to relate it to air in the water. Would also explain
why the total volume in the tank wouldn't change. Sounds like the
best explaination yet - even better since it doesn't relate to a
problem. (I don't think).
Bob

On Feb 14, 6:49 pm, "HeyBub" wrote:


Faucets are optimized to prevent stuff from going in one direction, not the
other.

The suckage may be much greater than normal water pressure anyway.

But how can it suck air into a tank that is full of water without
forcing some of that water out somewhere? Wouldn't there have to be
much less pressure inside the tank than outside? Since liquids cannot
be compressed, there would have to be air already in the tank for a
pressure differential.

But how can it suck air into a tank that is full of water without
forcing some of that water out somewhere? Wouldn't there have to be
much less pressure inside the tank than outside? Since liquids cannot
be compressed, there would have to be air already in the tank for a
pressure differential.

Which do you do first, turn the main on and then open the faucet?
or
Open the faucet and then turn the main on?

On 14 Feb 2007 17:02:30 -0800, "Bob" wrote:

On Feb 14, 6:49 pm, "HeyBub" wrote:


Faucets are optimized to prevent stuff from going in one direction, not the
other.

The suckage may be much greater than normal water pressure anyway.

But how can it suck air into a tank that is full of water without
forcing some of that water out somewhere? Wouldn't there have to be
much less pressure inside the tank than outside? Since liquids cannot
be compressed, there would have to be air already in the tank for a
pressure differential.


Hi Bob

Do you have an anti siphoning device on your water heater? This can
occur without one, either naturally or when work is done on the lines.
Around our area it's a standard item to have.

Regards
Dale

On Feb 15, 1:34 am, wrote:
On 14 Feb 2007 17:02:30 -0800, "Bob" wrote:

On Feb 14, 6:49 pm, "HeyBub" wrote:

Faucets are optimized to prevent stuff from going in one direction, not the
other.

The suckage may be much greater than normal water pressure anyway.

But how can it suck air into a tank that is full of water without
forcing some of that water out somewhere? Wouldn't there have to be
much less pressure inside the tank than outside? Since liquids cannot
be compressed, there would have to be air already in the tank for a
pressure differential.

Hi Bob

Do you have an anti siphoning device on your water heater? This can
occur without one, either naturally or when work is done on the lines.
Around our area it's a standard item to have.

Regards
Dale

No. But I don't see how it could siphon with the inlet valve closed.
That'd be like a finger over one end of a straw.

On Feb 14, 8:24 pm, "Lou" wrote:
But how can it suck air into a tank that is full of water without
forcing some of that water out somewhere? Wouldn't there have to be
much less pressure inside the tank than outside? Since liquids cannot
be compressed, there would have to be air already in the tank for a
pressure differential.

Which do you do first, turn the main on and then open the faucet?
or
Open the faucet and then turn the main on?

Does it either way. With the main on first, you can hear water
entering the tank so the air is in the tank prior to any valve being
opened. The more I think about it & discuss it, I'm leaning to air in
the water as it enters the tank, then separating as it sits. Water
comes from a saturated sand aquafir so I can understand how water
movement down there could induce air into the mix.

On Feb 15, 1:30 pm, "Red" wrote:
On Feb 14, 8:24 pm, "Lou" wrote:

But how can it suck air into a tank that is full of water without
forcing some of that water out somewhere? Wouldn't there have to be
much less pressure inside the tank than outside? Since liquids cannot
be compressed, there would have to be air already in the tank for a
pressure differential.

Which do you do first, turn the main on and then open the faucet?
or
Open the faucet and then turn the main on?

Does it either way. With the main on first, you can hear water
entering the tank so the air is in the tank prior to any valve being
opened. The more I think about it & discuss it, I'm leaning to air in
the water as it enters the tank, then separating as it sits. Water
comes from a saturated sand aquafir so I can understand how water
movement down there could induce air into the mix.

OOPS, used my alternate logon. Sorry.
Bob