The manufacturers instructions show the expansion tank installed with a 'heat trap 6" minimum' drop to the side of the water heater.

I have a tall 30 gallon (< 17" diameter) water heater going in a narrow closet (< 24"). The copper cold/hot lines come up from the floor. Is there a safe way to orient the expansion tank above the water heater instead of off to the side? Also is that heat trap 6" drop before the expansion tank required?

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1 Answer 1


They make heat trap valves, which come already installed on some water heaters. You could use those instead of the pipe loops, then you can route the pipe however you like. You should be able to find a set of heat trap valves for ~$10.

heat trap valve

Also, there may be alternative installation diagrams in the manufacturer's installation instructions.

Expansion tanks can be installed up, down, or on their side. However, if they're installed on their side, support is required.

  • 1
    Since the pipes come up from the floor, the "heat trap" in the manufacturer's diagram is effectively provided by the way the pipes route. The heat trap nipples/valves may have an effect of reducing water flow in your hot water pipes. They will help reduce heat loss, but you can also insulate the pipes above the heater and get pretty good efficiency without having to install the trap valves. Where I live, it is common to see the expansion tank positioned above the water heater.
    – Jonathan J
    Mar 16, 2017 at 18:51

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