You guys catch everything, well there is a drip leg already but it should be closer to the fixture it serves.
As for the tank being elevated here it’s not code to have a stand but if there is one we can leave it or drop it on the floor. What it’s supposed to do is prevent the water heater from...
Main is clogged somewhere, do you have a housetrap? If you do see if the water level is higher then normal then snak/rod/plunger from there. If the water level is normal then work it toward the house given that drain is close by.... where’s that drain located in the picture?
How is the flange is it plastic slip style where it just slides over the outside of the sch 40 pvc pipe or inside the pipe? Take a picture of the closet flange from above looking downward into the drain.
The sewer lateral is only 3”inch. Looks like your going to upsize that pipe to handle two bathrooms. What about clean outs? There is a limit on length/size for vents check to see how your outline measures up. Your going to need to know measurements of pipe runs.
It’s from above. Remove the spray head and hose, then take off the goose neck from above. You need a special grohe tool or crescent wrench [emoji373] to unscrew. Once you get the neck off you should see how to get it off. Or call grohe if it’s not clear enough.
The location of the tape measure is where the new shower drain is proposed? How about toilet and sink? Location of new walls, Sewer main under floor, installing new water lines for shower valve? Drawings/plans?