These strong polypropylene adapters are commonly used with our fresh water tanks equipped with 1-1/2" FPT fittings.

Just screw the 1-1/2" MPT end into the tank and then attach either a 1-1/4" or 1-1/2" diameter (ID) clear vinyl or green corrugated hose. A little silicone caulk on the barbs will act as pipe dope for corrugated hose.

A hose clamp finishes the job.

No thread tape is needed when screwing plastic fittings into polyethylene tanks. Just go one turn past hand tight.