What is this line coming from WH drain?

[mszenas]

Hello - I'm replacing a functioning WH due to age. Large 3/4 house with master BR on one end with large tub in master bath. This WH appears to have recirculating plumbing with a return line on top. see pic. There is no recirculation pump anywhere to be found and unfortunately, there is no access to the tub plumbing in master.

Here's my issue - at the bottom of the HW tank, there is a 'T' at the drain and a copper line with ball valve that goes up and into to the wall. It looks like this is original construction configuration. There's some foam insulation up where the pipe enters the wall. I have no idea what this is for? the pipe is cold to the touch all the time. Turning the valve closed does not seem to affect water flow anywhere... And this is NOT code. I need to get rid of it, but trying to figure out it's function first, so I don't create more problems... see pic. What is this for? Why? I'm stumped. thanks Mark

 

[Bird Doo Head]

Tees at the drain valve are often for the return line from a hot water recirculating loop. It may have been a gravity loop, thus the lack of a pump. (Sometimes gravity loops are called "Thermosiphon Loops").

But, that would make it a mystery why the line in the top photo isn't on the hot piping (unless I'm viewing the photo wrong).

In the photo, it looks like the top pipe goes into the wall. If so, maybe when the pipes are unhooked for the appliance change, blow low pressure air into one and see if it comes out of the other. That would confirm they are part of an old recirculating loop.
Paul

 

[mszenas]

Tees at the drain valve are often for the return line from a hot water recirculating loop. It may have been a gravity loop, thus the lack of a pump. (Sometimes gravity loops are called "Thermosiphon Loops").

But, that would make it a mystery why the line in the top photo isn't on the hot piping (unless I'm viewing the photo wrong).

In the photo, it looks like the top pipe goes into the wall. If so, maybe when the pipes are unhooked for the appliance change, blow low pressure air into one and see if it comes out of the other. That would confirm they are part of an old recirculating loop.
Paul

Thanks, it appears the return line from the loop t's into the cold supply as shown in the pic. I believe there's a check valve in the ball valve upstream. The top line, the hot line goes into the wall, yes. So, did they loop back into into the wrong line?

Anyway, we are starting to think that unknown line at the bottom is/was part of a heat exchange system with the outside AC condensor. that was original to the house and since disconnected...

 

[Bird Doo Head]

Thanks, it appears the return line from the loop t's into the cold supply as shown in the pic. I believe there's a check valve in the ball valve upstream. The top line, the hot line goes into the wall, yes. So, did they loop back into into the wrong line?

Anyway, we are starting to think that unknown line at the bottom is/was part of a heat exchange system with the outside AC condensor. that was original to the house and since disconnected...

I think you're on to something thinking they tapped the cold by mistake.
A house I once owned came with copper tubing from a tee on the cold water heater inlet. It teed into a far away sink's hot water supply and went back to a tee on the water heater's drain port. It also had a swing check. It never occurred to me that they might have simply done the recirculating loop wrong until I read what you just wrote.

A water cooled condenser for air conditioning is also a valid thought, although on a house system it would seem unusual. In some very old, large houses sometimes the built-in wood-and-tin refrigerators would have water cooled condensers, like many restaurants use for refrigeration units now. They were common where I grew up. Those refrigeration units had headmaster valves for flow control & the water that was warmed by the condenser would flow to the drain. They operated like chillers do to this day.

I can kinda-sorta visualize yours doing that, with the help of a pump, but when the water heater was temperature satisfied & no hot water was being used at a sink, the pump would send hot water in the now closed loop to the condenser- doing the opposite of cooling the refrigerant.
(And it would be ten kinds of code violations to mix domestic and condenser water since there is no isolated heat exchanger.)

Could it have been for a hot water finned coil in a duct work to heat a room? (Again with the code violations)

 

[GReynolds929]

Line on the cold is most likely feeding a hose bib. The line on the bottom is most likely a recirculation return line. Is there a pump somewhere?

 

[Bird Doo Head]

A stud finder with a metal setting or a metal detector wand may help you trace the pipes.
Tapping on a pipe with a little wrench while someone wanders around listening usually works.
A tone tracer might work if the pipe isn't near others where it's behind walls. (The tone will be on every pipe in the system. Follow the loudest tone.)

Once you cut the tubing as part of the water heater replacement, blowing compressed air gently through one or the other (or both) pipes might reveal the mystery. If air in Pipe A doesn't come out of Pipe B, have someone go around listening for air escaping in a wall or under a sink.

Whatever the pipes turn out to be, please let us know. It'll be interesting.
Hope it's not this:
After buying a house, a co-worker found copper tubing coming off her water heater and going into the wall, like your lower photo shows. She tone-traced it to the neighbor's garage hose faucet. I wonder how many car washings and lawn waterings she paid for?

 

[mszenas]

Line on the cold is most likely feeding a hose bib. The line on the bottom is most likely a recirculation return line. Is there a pump somewhere?

I don't think the bottom line is a recirculating line. it is as cold as can be. and the valve is very easy to turn like theres zero pressure inside... makes no noise when moved between on/off.

 

[mszenas]

Line on the cold is most likely feeding a hose bib. The line on the bottom is most likely a recirculation return line. Is there a pump somewhere?

Can't find a pump anywhere. that bottom line is cold to the touch. the valve is very easy to turn like there's no pressure in the line. also, it makes no noise when turned. I believe what i have here at the bottom is an old heat exchange line that ran out to the outside AC unit condensor. These sets up were very coming in Florida new construction in the 80's and 90's.
there's a big box on wall outside by the AC unit with 2 copper pipes going into it. I'm pretty sure once I get inside that box, those pipes are going to be crimped or capped off. That's what AC instalers would do when replacing the AC unit as these systems really wern't all that energy efficient. Make sense?

 

[Bird Doo Head]

Can't find a pump anywhere. that bottom line is cold to the touch. the valve is very easy to turn like there's no pressure in the line. also, it makes no noise when turned. I believe what i have here at the bottom is an old heat exchange line that ran out to the outside AC unit condensor. These sets up were very coming in Florida new construction in the 80's and 90's.
there's a big box on wall outside by the AC unit with 2 copper pipes going into it. I'm pretty sure once I get inside that box, those pipes are going to be crimped or capped off. That's what AC instalers would do when replacing the AC unit as these systems really wern't all that energy efficient. Make sense?

Having a water cooled condenser that recirculates back to the water heater doesn't make sense to me. As I described earlier, water cooled condensers are common, but the now warm water won't go into the water heater unless domestic water is being drawn off. If you do force it in, the existing hot water will go to the condenser. That won't cool the refrigerant to the liquid state.

Maybe Your House Had This:
Piping hot water through a finned heat exchanger (looks like a really thick car radiator) that is in duct work blowing air across it & into the building isn't uncommon.

Having one in a house isn't totally unheard of in warmer climates where the heat load is small or moderate climates where there are days that a heat pump can't keep up. Many mini-duct systems (like Hi-Velocity and Unico) offer such add-on coils for their units. The water is heated by a separate boiler.

In cold climates, most larger installations such as campuses, hospitals, office buildings use this finned coil with remotely located boilers producing hot water or steam. Some use utility company steam. Most of downtown Detroit is heated by that steam. Each zone has its own blower & control (usually pneumatic thermostat & valve) in one configuration or another. (Box on the wall, like a hotel or hospital room - Hidden duct in ceiling like office building, etc.)

Using domestic hot water for the heat exchanger is against every code and health statute under which I've ever worked. Maybe there are (were?) exceptions.

It'll be neat to find our what you discover!
Paul