Water tank on Sandpiper 5th wheel toy hauler 2005

[Scott Toy Hauler]

I have a 2005 Sandpiper 5th wheel toy hauler and the water tank under has both valves broken off. I understand you can "Spin Weld" new fittings on the tank?? Has anyone done this before?
Looks like one of the fittings which is where the valve is to empty the tank is 1 1/2" diameter and the water line coming out of the bottom is 1/2".

Any help would be greatly appreciated.
Thanks
Scott

[Blackrock]

Never heard of spin welding. I have done repairs to plastic AG tanks with fiberglass kits.