2 Plumbing Questions

I inspected a sink in an island which had neither an AAV nor a loop, just what seemed like an S trap. Is this wrong? Its new construction and seemed to have passed municipal plumbing inspections. I cant see anything else like where it leads to.
Also in a bathroom sink there is a water mixing valve which exits down from under the sink. I couldnt find where it lead to. Where would someone need such a mixing valve?

The trap certainly appears wrong, though we can’t see behind the cabinet back. Based on what is visible in the photo, I would document it as improper and put the onus on the builder to show that it is properly vented out of sight. Island vents and AAVs need to be serviceable (i.e., accessible cleanouts for the island vent)

The device that you see under the sink is an ASSE 1070 mixing valve. It will service the two handled tub faucet. As of IRC 2012 two handled tub faucets are required to be fitted with one of these devices to protect against scald injury. It should be adjusted so that the hot side does not produce water above 120°F.

I thought they were to be adjusted to 104 at the 2 handle tub.

Depends on your area’s regulation.

Thanks for the information. A tub has to have the scald protection but not a shower?

Both should have it…

All single handle tub/shower faucets have scald protection built-in. You won’t encounter a two handled shower faucet in new construction. The external device is only required for two handled faucets because scald protection is not inherent in their design.