I only have a 30 Amp RV Plug Receptable. I need to plug in a 20 amp cord that wraps around water pipes to keep them from freezing. Can I just use a 30 Amp to 20 amp pigtail and an adapter to change the plug in connection to 15/20 Amp?

Were you hoping for a cheaper way? Adapter, Nylon - Plug Adapters - Plugs and Receptacles - Electrical : Grainger Industrial Supply

Unfortunately a 30A RV receptacle is not the same thing as an L5-30 twist-lock receptacle.

This is what he needs: 30-15AMP CONVERSION ADAPTER Air Force BPA - Air Force BPA - Capitol Supply, Inc.

I'd say any RV or trailer store would have them. Or obviously online. ;)

For the life of me I don't know how they get these things approved. We are NOT allowed to put 15 or 20 amp general use receptacles on a 30A circuit, yet these adapters are readily available.