What is This??????

Can someone tell me what they think this could be? I shut the valve off and tested everything in and out of the house that I could think of and it didn't turn anything off. Could this possibly be the return leg of a circulation system? Even though there is no pump hooked up? I bought this house 2 months ago and for the life of me cannot figure it out.

It has an inline check valve above the shutoff valve which is why I thought it could be a circulation return. It comes just off of the main Hot water tank feed. Thanks for the help.

what direction is the check valve? flow toward the WH?
Then it is most likely a return line. does it get warm or hot?

No pump? if it gets warm, could be a gravity recirc system.

Thanks For the Reply! The check valve does flow toward the WH. It doesn't really get warm I wouldn't say but if it is a gravity system it may take quite a while to flow all the way around. I took a photo of the check valve. I assume there is no other reason or system that would require a return like this right? My old home had a recirc system but the configuration was different. I am going to add a pump and see what happens. I attached a picture of the check valve with the arrow pointing towards the heaters.

before you add a pump try just adding a hose bid between the check valve and the ball valve. close the ball valve and use the hose bib to bleed the air out of the line. the line will also get hot if it is indeed a return line.
it may work with out pump if you bleed the air out..

A gravity system return should be tied into the bottom of the water heater, Not the cold supply.

here's another thing that could be wrong. That is a swing check valve. Can't tell by your picture, but if that is on a vertical pipe and the water flow is going down toward the heater, then the swing check gate will always be open. gravity will keep it open. A vertical line with flow going down requires a spring check. Put the swing check valve on the horizontal pipe.

how-does-a-gravity-hot-water-recirculation-loop-work

Thanks man will give that a try. The check valve is on a horizontal line feeding towards the water heater cold water inlet. I can put the hose bib on but it will be on the horizontal line if that matters?