Here's the circuit. The 2 resistors are 1/4W or larger. The LM338 can be a T0-220 package. I had the lrager package on hand so I used it. Mount to a piece of alum to help with heatsinking. I used a reversing switch for the fill and empty function.
Here's the data sheet
http://cache.national.com/ds/LM/LM138.pdf
If you don't have the exact value resistors use the link below to see what will work:
http://www.electronics-lab.com/articles/LM317/

Dave Rigotti