Question
what is the spray you can paint on the wall to impede sucker growth you talked about in your 4/7/06 answer?

Answer
I did a quick google search, but could not recall the name of the product, and I don't specifically recall what paint I was refering to.  

The industry standard for root intrusion into irrigation pipe is a chemical called Treflan.  I think if you add it to your paint, that would probably do the trick.  It is a powerful substance, so read the label carefully, and the chemical protection only lasts about 10 years.

Talk to your local irrigation or landscape supply store (not the generic Big Box store).  Sorry.

-Marc