"I cleaned this carpet yesterday and today I went back because my customer called me back angry. There is a white powder all over the carpet! What did I do?!? Did I mix my cleaning products too strong?"
Do me a favor. Take a scrap piece of carpet in your shop or garage, mix your cleaning products*twice as strong as you normally do, spray the carpet twice as heavy as you normally do, and then just let it dry. Now take a look at it. Does that look anything like the white powder you ran into with your customer? Nope? Didn't think so.
Chances are (95% of the time#) what you are looking at is some sort of powdered, home-use carpet deodorizer, like "Carpet Fresh" or even plain old Arm & Hammer Baking Soda. These powders are extremely fine, and so over years of use, a lot of this stuff will settle through the face fibers of the carpet onto the backing where it is then forgotten. When you cleaned it the other day with your powerful cleaning equipment, you pulled a bunch up with your vacuum, and by wetting the carpet fibers you allowed even more to wick up as it dried. There is nothing you really could have done to prevent this, so you really haven't done anything wrong.
Now, even though this situation wasn't your fault, it's probably still a good idea to fix it for the customer (probably gratis, too). This situation requires a ton of dry-vacuuming. After you've dry-vac'd as much as you can, you might give a very light rinse with your truckmount (no prespray), using an acid rinse. Don't over-wet, or you'll be right back where you were at the beginning. In fact, if you are working on a low-level looped carpet, it might be better to run a bonnet instead of extracting (never run a bonnet on cut-pile carpet!).
*This only works if you're using stuff you got from us or another professional company. There are some cut-rate, home-brew products that can and will cause this kind of problem.
# Another 4.95% of the time it's disintegrating latex from the carpet backing. If the carpet is extremely loose, this might be a good indication that the white powder you're seeing is latex. If this is the case, recommend replacement. Also, in this particular case, you probably did screw up, since you should never clean a carpet that's not properly stretched. There's nothing you can do to fix this carpet, and in the customer's eyes it's your fault, so you may have to buy this one.
"My dehu shut off and it reads E9 (or Error 9 or Er9). What is going on?"
An Error 9 is the single most common "problem" with a Dri-eaz dehumdifier. I put "problem" in quotes, because it's usually not a problem at all. E9 is a pump-out problem, and 99.95% of the time it is simply a kinked or plugged drain hose. Sometimes if you are trying to run the drain hose to a point much higher than the unit, that can cause problems as well. If you get an E9 error code, just trace out your drain hose to be sure the water can flow freely. Once that's done, just restart the unit and it should work properly. If not, you might have fallen into the .05% of the time when your pump-out actually needs repair. If you do, just give us a call! We are an authorized Dri-eaz service center.
"My dehu has been running for an hour and the air's still wet! What the heck, maaaaan?"
Dehumidifiers are not magic. They take time to work. Typically, dehumidifiers don't really even start doing anything at all until they've run for an hour or so. Even once they start working, it's a slow process to remove all that water from the air. To facilitate the process, be sure your filters on the dehu are clean, and ensure that there is good airflow to the dehu. The dehu can't dry air that never passes through it.