I use hot tap water. Fill the holding tank and the bowl and soak my brush while I shower. Pour that water out then refill the holding tank and build my lather. I did find that the lathering technique is a bit different with the hot scuttle than with a cold bowl. But boy is it worth it.

Love my Dirty Bird 1.5 Scuttle. It may be a luxury that is not absolutely necessary but I'm worth it. LOL

Charlie