RIDGID Gray and White proprietary formulas are NFS and UPC listed and approved for potable water use. The non-toxic, lead-free formulas won’t harden or freeze, allowing easy disassembly of joints without compromising thread integrity.
 

RIDGID White Sealant with ultra-fine non-stick particles allows for tighter seal with less effort. The formula is not affected by oils, dilute acids or common solvents and can be used on PVC, CPVC, ABS, nylon, polypropylene, polybutylene, delrin, cycolac, as well as on metal pipes. RIDGID White Sealant should not be used on lines carrying oxygen, halogens or liquid sodium.

The Gray Sealant is a smooth extra-tacky paste that clings to the threads and provides a leak-proof seal. RIDGID Gray Sealant prevents thread corrosion and is approved for use in water, steam, air and natural gas, as well as in diluted acids, caustics, LPG and oil lines. RIDGID Gray should be used on metal pipes only.



http://www.ridgid.com/Tools/Thread-Sealants

Available at Lowes, Home Depot and many other hardware stores.