View Full Version : expantion tank location

10-31-2009, 03:07 AM
Simple question, does it make a difference where the expantion tank is located in a hot water system? I am tight for space near the boiler and am looking for alternative locations.

10-31-2009, 05:17 AM
It can be any where in the the system as long as there are no valves between the boiler and the tank.


Peter Griffin
10-31-2009, 05:29 AM
Ideally the expansion tank would be located near the boiler with the water feeder piped in below. that is the point of zero pressure differential. the circulator (s) should be installed past the tank, pumping away from the boiler.


10-31-2009, 07:36 AM
What kind of system is it? Hot water heating, or heating domestic hot water? The location of the tank is similar for both, in that it goes after the fill/feed shut off valve to the vessel. A domestic ET goes ahead of the storage tank, and the hot water heating one usually goes right on, or after, the boiler.

Peter Griffin
10-31-2009, 07:44 AM
I thought he was talking about a hydronic boiler system.
If it's a water heater the tank needs to go anywhere in the cold water line.

For hydronic, we like to come up off the boiler then hit an air eliminator with the feed piped below it and the expansion tank just below the feeder. That arrangement keeps the feeder from overfilling the boiler should there be a pressure differential. It is important that the circulator be piped past all of this otherwise you have defeated the whole purpose. Dan Holohans "pumping away" does a nice job of describing the specifics and providing piping diagrams. For years we just slapped the tank and fill wherever we could put them, mostly because boiler came packaged with the circ on the return. Manufactures did that because they could crate and stack boiler in the warehouse more efficiently. In a small residential system it probably would never be a problem, but when you start pumping long distances or up three stories it can make a huge difference in how the system performs.

10-31-2009, 03:00 PM
Many air eliminators have an air vent tapping on top and the expansion tank opening on the bottom.

Peter Griffin
10-31-2009, 04:28 PM
They sure do. I really prefer to use SpiroVent's unit.

11-01-2009, 03:11 AM
Thanks Guys you were a great help, the tank is now installed as in the latest reply.