We do a couple things...
In our initial proposal we state in writing and verbally that in order for them to receive the quality wash they are paying for, it helps by having all units spaced at least 6 feet apart, pulled away from the dock, fence, wall etc...
If that doesn't work. Then we fax them a nice reminder after we experienced a tight wash. On some of our bigger washes, we send a fax to them the day of or day before the scheduled wash reminding them that we are going to be on-site to do the washing.
This allows for a paper trail if ever they call you on your quality. All in all when we call the man/woman in charge they understand completely and will do almost anything to make sure they get a good wash for the money they are paying.
Hope this helps.
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Bridget
United Mobile Power Wash
Our Power Is In Our
Performance
WWW.WeWashTrucks.com