Average is beautiful

Pvc stack exposed to sun?

Is this an issue, or should it be painted to protect against UV?

How to alleviate mold smell coming from sink when pouring baking soda/vinegar/hydrogen peroxide/boiling water multiple times has done nothing?

Can someone point me towards the correct shut off valve for this application

Looks like I need a 1/2” female pex in, 3/8” male out, but with a T for an ice maker line. I can't find it. Or is there an easier way? Thanks

Basement 2” floor drain. Does have some water a couple inches down sitting. Is it possible to turn this in to a drain so I can dump water down there occasionally? Or does it not drain quick enough and what other solutions is there? Thanks!

Is galvanic corrosion of the gas pipe (on top) a concern here?

Is it bad that this expansion tank is installed this way?

Toilet/sink vent code question

I am installing a toilet and sink under a staircase and have limited options for venting. Can I use a 1.5” vent in the configuration of the drawing to vent both the toilet and sink? I am trying to avoid running a 2” vent through a top plate and support studs. I am in the U.S. (Louisiana)

Should I caulk these areas?

I circled the areas in red! The area circled in black on the bottom has an open hole, im assuming I don't caulk that? Thank you so much!

Toilet tank constantly losing water after it fills up.

I am having an issue with my dual flush American standard toilet. After I flush the toilet it fills up fine but slowly the tank leaks out and then it starts filling up again repeating the cycle constantly. I let it fill up and watched it slowly drown but can’t see anything going into the actual bowl not from the sides at least. What is my problem here? What do I tweak or what do I replace?

Loosen 1990s Kohler handles?