We use two K'A'rcher K2400H Gasoline Powered High Pressure Cleaners.
These machines spray water out at 2400 PSI using a 5.0 horsepower Honda GC160 Gas Engine. They have a built-in detergent injection system which allows the machine to pull just the right amount of cleaning solution straight from the bottle.
The Honda Engines are high performance and fairly efficient. They have a low smog index rating, which means that they don't harm the environment as much as a normal engine. They are very similar to the engines used on lawnmowers. Our GC160 model variations are AQHA and AQHAF.
Sites with Description:
Our Pressure washers --
http://www.karcher-usa.com/cpe/products/k2400hh.html
Their Honda Engines --
http://www.honda-engines.com/gc160.htm
Owner's Manual --
http://www.honda-engines.com/Engines_owners_manuals/ownersmanuals/31Zl8A04.pdf