[Vigilanteman]

Plumbers also have a marvelous sense of humor. One whom I call on says you only have to know three things to be a plumber:

1. $#*+ won't flow uphill.
   
2. Hot water pipe and faucet is on the left.
   
3. Cold water pipe and faucet is on the right.

[Don W]

1) S#1+ flows downhill
2) Payday is Thursday
3) Don’t lick your fingers

[Flint]

"Plumbers also have a marvelous sense of humor. One whom I call on says you only have to know three things to be a plumber:

1.$#*+ won't flow uphill.

2.Hot water pipe and faucet is on the left.

3.Cold water pipe and faucet is on the right."

You left off:

4. The boss is an SOB.

5. Payday is on Friday.

[RipSawyer]

I’ve heard it all my life in the South as, “Hot on the left, cold on the right and shit don’t run uphill.”

[catnipman]

oldest plumber joke in the book ... actually, the ONLY plumber joke in the book ...