domestic expansion tank????

Travis_4

I have seen this situation a couple of times and I'm wondering if anybody knows why it happens?
On a new hot water boiler system with an indirect the pressure relief valve sometimes leaks after 2-3 yrs in the beginning it is fine but after a couple of years the relief valve will start leaking. The fix on these two incidents had been a domestic expansion tank. I'm baffled as to why the systems never needed an expansion tank in the years previous? any insight would be helpful
!

Big Ed

Standard Question

I always get this question when I diagnos the problem..Here is some of the causes I have found..

Had water leak somewhere but has been fixed.

Back flow preventer added.

Water meter changed ,new one has built in check valve.

Old main check valve was stuck open but cleared itself.

Main pressure reducing valve has been added..

Increase in hot water temperature.

No one notice the pressure relief leaking before.

hot_rod

Increase in incoming water pressure?

hot rod

Al_19

What kind of indirect do you have?

When I serviced Boilermates(coil) years ago, this would happen when the coil got dirty after a couple of years and made hot water slower. If the homeowner filled up his jacuzzi say, the indirect couldn't keep up. The temp of the indirect would drop down to incoming cold water temp. Then it would run for hours to recover. The temp rise was from 55/60 degrees up to shutoff, which would cause the higher pressure difference and the relief to pop. It didn't always happen because if the hot water use was small, the tank temp would never drop way down. Or, if anyone uses hot water it relieves the pressure before the relief pops.

Mostly, I saw it happen after they filled the jacuzzi at night, then went to bed(no hot water use for the rest of the night). The next morning you would find the relief valve popped.

Weezbo

ST-12 is giving a small cushion to the expansion on the cold

water side... We have many different Quality fixtures and appliances in our home than 20 years ago...faster acting valves in washing machines and dish washers larger flow requirements in "Climate Centers"/ "anything everything you ever thought you would like your own individual environment to be "type showers...and the list goes on...thing is does your heat source keep up or does it lag...in the production of domestic hot water in these instances...without delving too deeply into the mechanics of municipal water systems lets just say , that depending upon where you live ,the season's , time of day... and a host of other minor technicalities...you can have varying water temps and pressures "available" and the environment from whence they came is often drastically different from where they end up...i consider it good practise to have an expansion type tank on domestic water heating equipment,in a way, it is important to me to see an anti scald devise and a check against flow back into the cold water side and the expansion tank...we live in This Century, things can be analyzed with Mathematica 6 . lawyers abound...best to go along with ,best practises , think things through and send your mind reading suit and clairvoiance glasses in NOW *~/:) younger people will have new things to consider in the future that we have yet to see....