Louise ann's Comments

 it's "carbon tetrachloride " 

WIKI

Surfactant (clear dish soap) stops the lava from sticking

Pickling salt solution changes the specific gravity of the solution (usually distilled water) and gives the lava float-a-bility

Louis, have you tried adding a solution of pickling salt water to the "tap water"

add a little bit at a time until the lava start flowing