pumped DHW tank

Barbarossa

The replies you offered were very good and some I did not consider on my first go around. With this additional input I have more to think about before the return trip. Many thanks folks.

Barbarossa

A backflow preventer was installed on the main water supply (by others) on a domestic hot water system. The safety valve would then simmer and spit because there was no expansion tank to relive the pressure rise. The system has a small circulating pump to keep the loop hot during occupied hours. We installed a bladder tank to deal with the expansion; it worked and we attached it to the line near the pump suction like on a hot water heat job. We were advised by the building management that we need to move the point of attachment to the pump discharge side. Any thoughts out there why this would be different? We feel the concept is equally valid for both applications. Thanks

STEVE PAUL_3

Most thermal expansion tank manufacturers want the tank installed on the cold water side so that the bladder is not subjected to as much heat. In theory I think it makes no difference except for the possible impact on the bladder and the warrantty.

WaterHeaterGuy

If I am reading this correctly it sounds as though you might have installed the expansion tank on the return line instead of the cold feed. While I doubt there are any factory intallation drawings showing it installed in that location, it should work fine. (I've seen them published on literature installed on both the hot and cold side... never the return line)

Also since it's building management and not the manufacturer (voiding warranties etc..) requesting the move perhaps some education to the customer on how the tank works may keep from you having to rework it.

jackchips_2

The tank will work

anywhere on the system that remains "open". If for some reason the recirc line is valved off (repairs, leaks) the relief valve will again do it's job as the expansion tank will be isolated.

I have always designed (commercial but should be the same for residential) the tank between the main cold water valve and the heater being especially careful if there is a check valve in the cold supply that the tank is also between that and the heater.

Jack

Larry Weingarten

One problem...

... you may experience is some hot water getting into the cold side when only cold water is used. The expansion tank can push hot water back through the cold inlet of the water heater. If the expansion tank were on cold piping, that wouldn't happen. It's not likely to be a serious problem ;~)

"Pumping away" doesn't apply to an open system.

Yours, Larry