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Mike16
12-08-2008, 11:57 AM
I recently had a new water pressure regulator installed on my house on the main water line. Now, the pressure reads a nice 65-70psi. However, I noticed that the lazy arm on my pressure gauge would spike to 120psi. I called my plumber back and told him that the valve must not be working correctly. He said he didn't think so and suspected that my "cheap home depot gauge" was faulty. He left his gauge on (without a lazy arm) for me to check to see if I could ever catch the high pressure.

However, after reading this forum, it gave me a clue that the pressure increase could be due to thermal expansion. And sure enough, I have found that the pressure increases when the water heater turns on. The pressure will spike up to 120psi. Of course, as soon as a faucet is turned on anywhere in the house, the pressure goes back to normal.

I don't believe I have any thermal expansion tank, at least I don't see one connected to my water heater. Should this be something I should consider having installed? I would imagine that during the day, any thermal expansion is quickly dissipated by water use. However, at night I'm not sure if the pressure stays high or slowly dissipates on its own.

Thanks for any input.

Redwood
12-08-2008, 11:59 AM
Installing one could increase the service life of your water heater.
The extra 40 PSI isn't enough to cause the T&P to release water but in a pressure vessel there is a certain number of expansion cycles that it can take before it tells you replace me!

This is a picture of a failed pressure vessel that had to many expansion cycles on it.
http://i44.photobucket.com/albums/f2/Redwood39/243a.jpg http://i44.photobucket.com/albums/f2/Redwood39/side2.jpg
Aloha Airlines Flight 243

Keep flexing that water heater tank and say Aloha Baby!

hj
12-08-2008, 12:08 PM
It shouldn't affect the water heater one way or the other. What could be affected is the washing machine hoses and the small supply lines to your faucets.

SteveW
12-08-2008, 05:22 PM
Once I learned, from this very forum, of the need for an expansion tank, and installed one, my water softener has not needed annual replacing of o-rings and rotor discs.

Long-term high water pressure is like high blood pressure - it takes its toll.

Get an expansion tank installed, and have a shut-off valve installed right under it so that when it eventually fails, you can isolate the tank to make replacement easier.

In my case I also had a boiler valve installed so that I would have an extra hose bib, so I could watch the pressure with/without the expansion tank on line. It's fun to shut off the valve to the tank, let the water heater heat up a batch of water, and watch the pressure gauge go to 100...120...150...even 180. Then open the valve to the tank and the pressure comes immediately down to whatever the PRV is set at.

Redwood
12-08-2008, 05:30 PM
In my case I also had a boiler valve installed so that I would have an extra hose bib, so I could watch the pressure with/without the expansion tank on line. It's fun to shut off the valve to the tank, let the water heater heat up a batch of water, and watch the pressure gauge go to 100...120...150...even 180. Then open the valve to the tank and the pressure comes immediately down to whatever the PRV is set at.

This is not something I would recommend doing! The T&P should release the pressure at about 150 Psi.

http://www.waterheaterblast.com/waterheaterblast.wmv

nhmaster
12-08-2008, 07:11 PM
Most codes require a thermal expansion tank installed on the cold line. Since the PRV has a check valve that will not allow expansion back into the city main the pressure has no where to go. Your plumber should have known this and installd the tank when he installed the PRV.

Dunbar Plumbing
12-08-2008, 09:56 PM
It shouldn't affect the water heater one way or the other. What could be affected is the washing machine hoses and the small supply lines to your faucets.




Ahh.....but it does.


Water heaters these days are built with such a thinwall spec that expansion and contraction of that tank scribes tiny microscopic hairline cracks in the walls of the tank. Those cracks will sometimes leak, cancer out and seal off. Sometimes there's a bunch of them on a water heater and then one "bigger" one decides to let go and never seal back up. Consider it like a set of lungs that grow and shrink.

Metal has flex tendency but given the nature of aggressive water, glass lining so thin and a anode rod that's life is gauged long enough to get past warranty, it's a sure fire bet that large pressure spikes can affect the tank along with what you mentioned.


Job security for us all which is great, but the tanks built today are so vulnerable by just their design that it's sickening to know people will be replacing their heater numerous times in a 30 year period of living at the same home.

This wasn't like this back in the 60's, 70's.

In today's market, a tank lasting 20 years? The mfg. would look dumbfounded and say,

"What in the hell did we do wrong here?!"



.

kingsotall
12-09-2008, 05:09 AM
This wasn't like this back in the 60's, 70's.

In today's market, a tank lasting 20 years? The mfg. would look dumbfounded and say,

"What in the hell did we do wrong here?!"



.
Just like every other apllaince out there... Yup, it's sickening, but job security nonetheless.

burleymike
12-09-2008, 08:30 PM
It sure is sad they don't make them like they used to. A few years back my cousin was going to make a BBQ out of an old water heater. The unit we got was 50 years old and it was 3/16 galvanized steel. He decided using a galvanized tank was not a good idea so we scrapped it.

The 10 year old tank we got was probably 1/8 steel. Older is sometimes better.

Cass
12-10-2008, 04:32 AM
Since the PRV has a check valve that will not allow expansion back into the city main the pressure has no where to go.

Pardone Misure

Most will back flow / spurt, under some conditions, if the house side pressure exceeds the street pressure...

Check the spec. here...

http://www.watts.com/pdf/es-25aub.pdf

hj
12-10-2008, 06:01 AM
I doubt that any heater, other than an ASME rated one, is made with even 3/16 steel. We have many areas with standard pressures over 100 psi, and LOTS of "closed sysem" water heaters, and the heaters do not go bad any sooner than those with expansion tanks.