I lay it out on the driveway and use a Bissell Big Green Machine to spray the carpet cleaner on, then scrub with a brush. Then hose off with a hose and vacuum as much water out with the Bissell. Then lay out in the sun to dry. I have a light colored carpet and do it once a year.. Still looks like new.

Mine had a little mold this year, i did as others above have, soaked it and scrubbed with a stiff brush, then powerwashed it and hung over fence for a couple days it bright sun to dry and uv makes mold die.

I pressure wash, but I use an electric not a gas so the pressure isn't to high. I use Tide laundry detergent....get it wet and soak for about an hour with detergent before pressure washing. I also flip over and rinse the back to get ALL of the soap out.

Hang on fence and let dry in the sun, until COMPLETELY dry.

There is no right answer here, it is interesting to see how others do it and I may try some of the ideas.

Beat the dirt out???? what are you going muddin' or something

Depending when/where you boat around here....you just might be.

There wasn't much dirt in it since I only allow bare feet. The car wash worked great and now the carpet is hanging on the deck to dry.

After cleaning and fully dry, I follow-up with a couple light coats of 303 Fabric Guard. This gives UV protection to prevent fading and repels dirt. Had a passenger accidently spill a beer and it was amazing how it just rolled off and drained into the bilge.

http://www.amazon.com/303-30616-Fabr.../dp/B0000AY69N

Visual aide.
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Peoria Lake comes to mind.

Simple Green, hose or power washer, hang to dry in sun. I have, on occasion, added just a hint of bleach to the Simple Green.