Series water heater explanation

[VAWellDriller]

I have a 2nd home at the beach, which has 2 electric water heaters plumbed in series.

I understand the basic setup but one thing is very curious to me. On the 2nd water heater in line (on left) they have a line feeding it from the bottom. They installed a tee with a boiler drain and a pipe running into the unit....there is a check valve on the bottom feed line. Can anyone explain this to me or have ideas? The rest of plumbing is hidden..can see anything. Is it some sort of recirc line?

 

[Reach4]

Return line for a recirculation system. There will probably be a pump that takes hot from somewhere far, and pumps it into the recirculation return. It is possible to have gravity-driven recirc, but that would normally not use a spring-loaded check valve.

Ideally they would have put a tee into the low port to let you have a sediment drain valve in addition to the circulation.

 

[Sponsor]

 

[VAWellDriller]

Return line for a recirculation system. There will probably be a pump that takes hot from somewhere far, and pumps it into the recirculation return. It is possible to have gravity-driven recirc, but that would normally not use a spring-loaded check valve.

Ideally they would have put a tee into the low port to let you have a sediment drain valve in addition to the circulation.

There is a tee and drain. If there is a pump I haven't found it yet....it's not anywhere visible. Maybe it's gravity. Thanks for input.