MAKE-UP WATER AND EXPANSION TANK RULE OF THUMB FOR SIZING?

Joel Pickering

Is there a quick rule of thumb or chart that can be used to size piping to an expansion tank, or make-up water pipe for hot water systems? I know how to size piping mains and branches from system GPM, but is there a quick way or rule of thumb used to estimate these other two line sizes?
Thanks in advance for your help,
Joel

Unknown

Usually need at least 3 things.

gallons of water in the system, water temperature range, and BTUH.

Then you can size it for whichever brand tank and their charts.

Noel

Mark Wolff

boiler makeup line and exp. tank

For the cold water boiler feed (boiler makeup), 1/2" water supply is standard and more than adequate until you look at huge systems (schools, factories, etc.). Even moderately large heating systems shouldn't need much makeup water, if they do, there's a leak. Watts and Taco both make good pressure reduction valves w/ fast fill valve (important for filling and flushing!)

For the expansion tank, the actual tank sizing can be based either upon the btu output of the boiler you are connecting to, or upon the planned high temperature of the system and number of gallons of water in the system. Amtrol makes one of the most common and widely accepted units called the Extrol. For the piping to that expansion tank, once again, 1/2" is all that is needed. Even on a system capacity of nearly 200 gallons of water the tapping on the tanks only runs 1/2" MIP.

On domestic hot water expansion tanks the threads are 3/4" MIP, and 3/4" piping would be required there.