Hi, Mike.
That appears to be a return register. Unfortunately, not enough information.
Age of build.
Lot slope.
As to the return register. Outside wall?
Unmount the duct register. Look into the register and tell us what you see. Look for corrosion and how far the corrosion extends.
As for the column next to the cast iron cleanout.
You see bulk water? The water we drink and bath in?
IMO. The ductwork is good area for condensate to be created. Bulk water follows in the direction of slope.
Column. Posable plumbing fault. Drain clean out cap leaks or ruptured pipe. Either or…
As for the lot drainage experts.
Did any of the experts scope the weeps tiles or do a preliminary excavation to assess the perimeter drainage field near that SUSPECT area? If not, highly unusual for experts. Lol…
Story.
Client. 2 year old home. One foundation crack. exposed.
No efflorescence. No abnormal moisture in wood or concrete. All normal/average.
The basement window leaked when they watered the 2 >< 7 foot conifer tree next to the basement window.
A: I told them remove the trees. B: I told them to caulk the basement window. C: Have the crack injected with polyurethane.
Moving forward. They did not want to bother me again.
They called in 3 specialists, all excavation contractors that do perimeter drainage and injection work.
All 3 said they required new perimeter drainage and weep tiles. Prices ranged from <15,000 to > 30,000 all sides.
Remember. This is a 2 year old house.
They all said they required a new perimeter drainage system and weep tiles. Same scenario. Exterior. Interior. Mixed exterior and interior. LOL!!!
I passed by free of charge and did an analyse with all my tools.
Only one of the excavator foundation repair specialists came back with a reply. No apology. An estimate for $2,000 to inject 6’ feet of concrete. They had to prepare all the surfaces prior the work and replace the drywall at there own expense.
This excavation company works for real estate brokers.I know them now for ><15 years. I did the same work on occasions only professionally.
I have 2 seller’s declarations with invoices of that company charging $570.00 to repair 3 cracks of the same dimensions on 1 property. A legal declaration. Hm? Damn straight legal. Legal enough to tie them up in claims court.
I told my clients to make a consumer complaint on all three companies.
Good luck.
Robert