For the past 40 years I have installed 4- 40 gallon hot water tanks (natural
gas) in my home.
Today I picked up a new 30 gallon tank, installed it, fired up and could not
believe the pressure rise as temp increased, went to 140# and still going at
120 deg temp
My incoming pressure is usually 90psi, give or take 10 #
I know I am going to need a press reducing valve, either for the entire
system, or the hot water tank itself, or an expansion tank for the hot water
tank.
Question is why in the world am I having pressure rises like this on the new
tank, and never had this problem before ?
thanks

On Nov 28, 7:52*pm, "jimmy" wrote:
For the past 40 years I have installed 4- 40 gallon hot water tanks (natural
gas) in my home.
Today I picked up a new 30 gallon tank, installed it, fired up and could not
believe the pressure rise as temp increased, went to 140# and still going at
120 deg temp
My incoming pressure is usually 90psi, give or take 10 #
I know I am going to need a press reducing valve, either for the entire
system, or the hot water tank itself, or an expansion tank for the hot water
tank.
Question is why in the world am I having pressure rises like this on the new
tank, and never had this problem before ?
thanks


Your water heater cannot create a system pressure rise unless your
water system is a "closed" system.

Do you have a check valve or back-flow preventer somewhere in the
system?
If so you need a system pressure relief valve or an expansion tank.

Run some water out of a hot water valve in the bathroom or kitchen
(about gallon or so) and see if the pressure drops.

My best guess is that the expansion of the water in the water heater
from cold to hot is pressurizing a closed system.


cheers
Bob

On Nov 28, 10:52*pm, "jimmy" wrote:
For the past 40 years I have installed 4- 40 gallon hot water tanks (natural
gas) in my home.
Today I picked up a new 30 gallon tank, installed it, fired up and could not
believe the pressure rise as temp increased, went to 140# and still going at
120 deg temp
My incoming pressure is usually 90psi, give or take 10 #
I know I am going to need a press reducing valve, either for the entire
system, or the hot water tank itself, or an expansion tank for the hot water
tank.
Question is why in the world am I having pressure rises like this on the new
tank, and never had this problem before ?
thanks

Sounds like you have a check valve in the supply line to your hw
heater. You should install an expansion tank on the line at your hw
heater. They make small ones that can be supported by copper pipe
without additional bracing. If you have some other piping you may
need to support it. Lowes and home Depot both usually carry them.
Typically around a $100. If you are on a well then your normal
storage tank should handle the expansion. Look for a chack valve
somewhere between the hw heater and the well tank.

jimmy wrote:
....

My incoming pressure is usually 90psi, give or take 10 #
I know I am going to need a press reducing valve, either for the entire
system, or the hot water tank itself, or an expansion tank for the hot water
tank.
Question is why in the world am I having pressure rises like this on the new
tank, and never had this problem before ?
....

I'd venture the existing PRV has failed and you weren't aware of it
before...

90psi is about double what normal residential water pressure is.
Amazing haven't blown toilet valves, icemaker, washing machine control
valve, etc., etc., etc., ...

Any water system is a "closed system" when not running; otherwise
there's no holding it in.

--

jimmy wrote:
For the past 40 years I have installed 4- 40 gallon hot water tanks
(natural gas) in my home.
Today I picked up a new 30 gallon tank, installed it, fired up and
could not believe the pressure rise as temp increased, went to 140#
and still going at 120 deg temp
My incoming pressure is usually 90psi, give or take 10 #
I know I am going to need a press reducing valve, either for the
entire system, or the hot water tank itself, or an expansion tank for
the hot water tank.
Question is why in the world am I having pressure rises like this on
the new tank, and never had this problem before ?
thanks

Maybe you got all the air out of the pipes this time.

Or, you added a check valve or pressure reducing valve since last time.

On Nov 28, 7:52*pm, "jimmy" wrote:
For the past 40 years I have installed 4- 40 gallon hot water tanks (natural
gas) in my home.
Today I picked up a new 30 gallon tank, installed it, fired up and could not
believe the pressure rise as temp increased, went to 140# and still going at
120 deg temp
My incoming pressure is usually 90psi, give or take 10 #
I know I am going to need a press reducing valve, either for the entire
system, or the hot water tank itself, or an expansion tank for the hot water
tank.
Question is why in the world am I having pressure rises like this on the new
tank, and never had this problem before ?
thanks

Some water heaters come with a connector nipple on the cold side
(inlet) that have a plastic ball in them that acts as a check valve.

On Nov 29, 10:06*am, dpb wrote:
jimmy wrote:

...

My incoming pressure is usually 90psi, give or take 10 #
I know I am going to need a press reducing valve, either for the entire
system, or the hot water tank itself, or an expansion tank for the hot water
tank.
Question is why in the world am I having pressure rises like this on the new
tank, and never had this problem before ?

...

I'd venture the existing PRV has failed and you weren't aware of it
before...

90psi is about double what normal residential water pressure is.
Amazing haven't blown toilet valves, icemaker, washing machine control
valve, etc., etc., etc., ...

Any water system is a "closed system" when not running; otherwise
there's no holding it in.

--

No, few suburban household water systems are "closed". The service
entrance means it's not closed. For many years hw expansion pressure
was absorbed by the service line coming in. Rural might satisfy the
definition of closed but well systems almost always have storage tank
that doubles as an expansion tank.

On 11/28/2010 9:52 PM, jimmy wrote:
For the past 40 years I have installed 4- 40 gallon hot water tanks (natural
gas) in my home.
Today I picked up a new 30 gallon tank, installed it, fired up and could not
believe the pressure rise as temp increased, went to 140# and still going at
120 deg temp
My incoming pressure is usually 90psi, give or take 10 #
I know I am going to need a press reducing valve, either for the entire
system, or the hot water tank itself, or an expansion tank for the hot water
tank.
Question is why in the world am I having pressure rises like this on the new
tank, and never had this problem before ?
thanks



jamesgang has the correct answer. your new heater has a check in the
inlet. Take it back apart and throw the somebeach in the round file.
THEN put an expansion tank on, (anywhere in the entire system is fine,
they don't have to be right next to the heater).

--
Steve Barker
remove the "not" from my address to email

Thanks everyone, found the problem
This past summer had the main line replaced..all the way to the meter, a
pressure regulating valve along with a back flow preventer was also
installed making this a closed system.
I forgot all about it until now. expansion tank will be installed way we
have had 80lbs pressure for the 40 years lived here.recently went to 90,
inlet press, I don't know if I could live with 40#...before we had main line
replace pressure dropped to 20# when ever a valve was opened...
I may consider dropping the inlet# tho
thanks again everyone
"Steve Barker" wrote in message
...
On 11/28/2010 9:52 PM, jimmy wrote:
For the past 40 years I have installed 4- 40 gallon hot water tanks
(natural
gas) in my home.
Today I picked up a new 30 gallon tank, installed it, fired up and could
not
believe the pressure rise as temp increased, went to 140# and still going
at
120 deg temp
My incoming pressure is usually 90psi, give or take 10 #
I know I am going to need a press reducing valve, either for the entire
system, or the hot water tank itself, or an expansion tank for the hot
water
tank.
Question is why in the world am I having pressure rises like this on the
new
tank, and never had this problem before ?
thanks



jamesgang has the correct answer. your new heater has a check in the
inlet. Take it back apart and throw the somebeach in the round file. THEN
put an expansion tank on, (anywhere in the entire system is fine, they
don't have to be right next to the heater).

--
Steve Barker
remove the "not" from my address to email

On Nov 29, 12:46*pm, wrote:
On Mon, 29 Nov 2010 09:30:20 -0800 (PST), jamesgangnc





wrote:
On Nov 29, 10:06*am, dpb wrote:
jimmy wrote:

...

My incoming pressure is usually 90psi, give or take 10 #
I know I am going to need a press reducing valve, either for the entire
system, or the hot water tank itself, or an expansion tank for the hot water
tank.
Question is why in the world am I having pressure rises like this on the new
tank, and never had this problem before ?

...

I'd venture the existing PRV has failed and you weren't aware of it
before...

90psi is about double what normal residential water pressure is.
Amazing haven't blown toilet valves, icemaker, washing machine control
valve, etc., etc., etc., ...

Any water system is a "closed system" when not running; otherwise
there's no holding it in.

--

No, few suburban household water systems are "closed". *The service
entrance means it's not closed. *For many years hw expansion pressure
was absorbed by the service line coming in. *Rural might satisfy the
definition of closed but well systems almost always have storage tank
that doubles as an expansion tank.

Back flow preventers have been in the code for years. Most services
are not "open" if you live in a fairly new neighborhood.
The pressure rise should go away immediately as soon as he opens a hot
water valve.- Hide quoted text -

- Show quoted text -

I think it's safe to say that well in excess of 90% of suburban homes
still have nothng between them and the city water supply. The op
found out he does have one. But I can tell you my neighborhood of
1,200 homes was built within the last 20 years and none of them have a
check valve, regulator, or backflow preventer between the city supply
and their water system. Except for irrigation.