Power Washing House Bricks

My neighbor and I are going to share the rental of a power washer but don't know how powerful of one to get. He has the toughest task; removal of mud stains from around his house. His bricks are antique white (I assume the color and pattern are baked into the bricks and not just a surface coating). After he built his house about seven years ago, he didn't seed right away. The rains kicked up the mud and formed the stain. He used a 2000 lb pressure washer once. It still left a shadow.
Questions: Q1) Is a 3000 lb unit likely to do the job? Q2) is there a chemical he should add?
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wrote:

Danger, Will Robinson, danger!
Consider posting your question on alt.home.repair.
Never assume anything. I'd bet a pizza the bricks are merely coated. {If I'm wrong, I'll even help you eat the pizza.}
As for the shadow that survived the 2K psi, I'd treat it with a bleach solution; keeping it wet for at least 20 minutes. Then rinse.
You can do a lot of damage with 3K psi; so, be careful.
For removal of serious dirt, its hard to beat trisodium phosphate. AKA "TSP".
Jihad Joe--fighting man, from towel to toe.
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