Water leaking under Tub when filling tub

[xnay]

Hello, I thank you for your time. I'm hoping you can help me troubleshoot an apparent long standing issue with my upstairs bathtub. It seems that whenever the tub is filling, water is leaking somehow from somewhere under the faucet and valves onto the downstairs ceiling drywall. I haven't been able to specifically identify where the leak is coming from. It is not from the drain, as I initially thought, I've re-puttied it, filled the tub and let stand for hours, then drained, no water leakage. It's definitely leaking down when the water is actually running. When the water is off, there is no leaking, only when the water is running. I've taken the cartridges out of each valve and ispected, they 'look' good, I don't see water leaking from them when the water is running, so I 'assume' they're good. I see no leaking from the top whatsoever. I haven't been able to figure out how to remove the spout to possibly get a better look at what's going on underneath when the water is running. I've cut a hole in the downstairs ceiling drywall to try and get a better assessment but I can't quite get a good view because of the tub framing and tight clearances, but I can definitely see water pouring down when the tub is filling.

Any insights you can offer will be greatly appreciated. I'm hoping to not have to rip into carpet and plywood and praying it's an issue I can repair myself from top, as money is tight right now. I've taken a few pics to help visualize my setup.

 

[Ben-gee]

Most likely is the connection between the inlet valves and the spout.

I doubt very much that you can sort it from above. Time to get a look underneath - May be possible to come through that wall on the left - hopefully it’s the back of a wardrobe......

Although could always come in through those steps - carpet is far easier to remove replace than the more common tile - so you’re not in too bad a position really.

 

[xnay]

Thank you Ben-gee, for your insight. Yeah, I'm with you on the cutting through a couple of drywall boards to get access. It's not a closet on the other side of the wall, but it still seems better than trying to mess with removing the carpet and plywood to gain access. I'm curious if you could help elaborate on what to expect underneath. I'm thinking that there are a couple of copper pipes coming out from the valves to a tee, and from there to a single pipe outlet, as shown in my spout pic. So basically, the water is leaking from a joint either at the outlet of one or both of the valves, or at the tee, or possibly a piece of copper needs to be replaced. All of these scenarios would require a torch and solder to repair, no? Can you think of any other possible conditions to expect?

 

[oz-plumber]

You may not need a torch and solder.
Sounds like a leak in the breaching piece or the connections.
It may only need a nip up with a spanner.
Only visible inspection will tell you.

Get a camera that can be fitted through a 10mm or 12mm hole and see what you can find.

 

[JCplumb]

The underside view of that tap spout is unusual.
If water comes out of the end of the copper tube part then I'm guessing some is running back along the outside of the tube and through the tap body.
As a test you could fill the gap where the copper tube part disappears with silicone, let it dry and see if that stops the leak. If so you need a new tap.