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