Electric Water Heater Piping

Red - Likely and expansion device. (Hence why asked for a close-up and any markings) Which would satisfy the thermal expansion tank/device requirements.

Blue - Likely discharge piping for expansion device. Where does it go? Outside?

Also, very nice manifold system. Main shut-off device is partially closed.

Here is a close up of the valve.

There we go. This is flowing away from the tank. That is not a supply in, but rather a discharge out. Any markings on the other side? I would bet a dime to a dollar this is an expansion device.

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Looks like a poppet style pressure relief valve on the cold water supply.

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I am having trouble determining what is considered an “approved thermal expansion device” in lieu of a thermal expansion tank. Do you think this poppet valve qualifies?

The other side of the valve also has the directional arrow and the name Apollo. I thought expansion tanks/devices were supposed to be on The hot side.
Thanks for all the info.

I know right!

But no, they are on the cold side. (exception, non-potable water heating systems)


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Thanks for clarifying.

Yes as it is still a thermal expansion device.

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That’s the info I needed

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It can be rather tedious. But the pay off is huge. I have a hunch many inspectors are calling out missing thermal expansion tanks when an expansion device may be present. Thanks for the help. @msmith104 Good post!


The thermal expansion valves I see are integrated into the shut off valve.

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Sneaky. :grin:

This whole thing got even better after my initial post. Thanks for the valuable insight. You guys are great


Thanks everybody barest info. I appreciate you.

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I am thinking that a licensed plumber didn’t install this water heater from the look of the water line contraption.

That is the difference between thermal expansion, which is only for the expansion of the water heater), and a pressure relief for the entire home (cold side) these can be at the location you see here, or it can also be at the main water shut off outside the home, which is more common.
Then you also have pressure regulators, which are different from pressure relief (both on the cold side)

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I believe thermal expansion tanks or devices go on the cold side on a closed system and are to be located within 18" of the tank. @mwilles may be able to support this statement or correct me if I am wrong.

There is a difference between thermal expansion device and a temperature pressure relief valve which is attached to the tank. I do not have all the science down but I am working on better understanding.


Yes, my bad… the thermal expansion tank goes on the cold side.
But the pressure relief for the whole house also goes on the cold side, and I believe can be anywhere in the home after the main shut off valve