Tankless Water Heater & Thermal Expansion Tank

[scenet2]

Hello, I just moved into a house that have a tankless water heater and a thermal expansion tank. I thought thermal expansion tank is only required for a traditional tank water heater. My question is: should I remove the thermal expansion tank or keep it because I was told it's good for the piping system.

Thank you in advance for any advice.

 

[FishScreener]

Looks like the tankless is a retrofit, and then tank is a holdover from the old system. Doesn’t hurt anything for it to be there. So, I’d leave it alone.

 

[breplum]

If there are any check valves on cold water pipe, which it does not appear to have, or a pressure reducing valve on the water main, that does not have bypass...those are situations where the exp. tank is required.