[villagetinker]

Originally Posted by Laker14

Thanks. Do you have any specific recommendations for me, so I can avoid that? I didn't know this was an issue.

You will need to read the manual, if you no longer have it, then the stores that sell pressure washers have solutions specifically designed for this use. As I recall bleach (chlorine) is specifically NOT recommended. I wish I could recall the name, but the one I typically use is a purple colored liquid, works very well. I need to get some soon.
The other thing that works very well is snow cap, which is a powder that you put into a garden sprayer and spray on the walls. It does a great job of removing the stains from irrigation water. I typically do this first that go over with the regular pressure washing.