The factory valves are Bristol. I just changed the black tank valve seals (3"). The kitchen (galley) tank valve is 1.5".
Lasalle Bristol 39227 Seal Kit for Waste Valve - 3"
https://a.co/d/6OuxnAJ
Lasalle Bristol 39225 Seal Kit 1-1/2" F/Waste Valve
https://a.co/d/7CH2cLz
On the front drop down its a Fairly easy job. Hardest part is putting the coroplast back up.
Fasten one side then use two 8' 2x4 on leveling blocks to hold up the boards to hold up the coroplast until you get it fastened back up. Awkward.
While I had it open I added lubrication ports to the valves. They slide VERY smoothly now. And I added insulation around the frame perimeter and bottom.
SmartSHIELD -20mm 48"X25ft Reflective Insulation Roll, Foam Core Radiant Barrier, Thermal Foil Insulation Panel - 0.8 Inch Thickness, R-23
https://a.co/d/dSL37BE
Valve lubrication making lube holes for silicon grease