Hi, we just bought our first home (it's a complete fixer upper but was supposedly custom built by the owner of a company that built houses in the 60's and early 70's).

I'm remodeling a bathroom and can't make sense of this pipe setup:



Picture is from the closet wall being opened behind the bathroom.

The picture shows the first sink. You can hardly see it, but the cold water supply pipe is hidden beside the 2x4.

The question involves the hot water pipe. why would there be a second pipe that's even attached above where it shoots off to the sink? It is not the same for the other sink and is not setup that way anywhere else in the house. Also, it has nothing to do with how the hot/cold continue to the second vanity. The pipe runs off to god knows where.

Thank you!

PS: There is also a weird copper pipe I'm trying to figure out coming from the water heater downstairs. Even locating the water heater manual I see nothing about why they would have added connector pieces that attach a copper pipe from what I believe is the drain valve -- the pipe runs FAR through-out the house. I haven't fully tracked it yet, but it's over 50' and runs along with the other hot/cold copper pipes to the rest of the house. I'm wondering if this is where it leads and maybe it's an overflow system or something along the lines of water comes from the water heater in the basement and then this is a way for it to get back down? Although I haven't seen anything like that in books on plumbing a bathroom or in the manual on the water heater. I also see that all of the plumbing (sinks/showers) have an extra extension of copper and a T connector. I'm wondering if that's old school plumbing and found to not be needed since the books I see on plumbing I haven't seen that before and see just a 90 degree connector turning the pipe to the sink without needing a T connection and extra pipe extended upwards.

Last, we have well/septic if that makes a difference.

Thanks so much for reading this far!

Additional photos...

Here's the view from below the upstairs double vanity:



Here's 2 pictures of the unknown bottom water heater copper pipe since I can't figure that one out either and wonder if it's linked to the pipe above.



I believe the spot on the water heater is the drain valve hole. The first part going straight out could make sense to drain the unit (although I thought that was what the plastic white pipe was for). However, the part how it has a T connector that then has a copper pipe going up and later following along the hot/cold pipe I don't understand what it's for.



Edited 1 times.

Actually, is that extra pipe on the vanity COMPLETELY normal and that's simply how the hot then goes to another room?

I'm learning as I go and I THINK there is originally just 1 hot and 1 cold coming from the water heater.. so somehow that has to split off to all of the bathrooms/laundry/kitchen so maybe that's all it is? That's an upstairs bathroom but there's also a master bathroom nearby so maybe that pipe goes off to there.

The extra pipe at the water heater is for a gravity recirculation system. It constantly allows hot water to flow throughout the home so that you won't have to wait long for hot water to arrive at the fixtures.
The other pipe at the sink may have been home made air chambers, they suppose to prevent water hammer, but after they fill with water they are useless.

The second line is a recirculation line, but without a check valve, and maybe a pump, it is useless.