If you will store gas for any length of time you should add a fuel stabilizer as well. 

The high-pressure electric power washer is designed to be used with cold or lukewarm water; higher temperatures can damage the pump.

Do not use water that is dirty, gritty, or contains any chemical products, as such impurities could impair operation and shorten the life of the machine.

Refer to following link for usage instructions --> Manual, Manual 2

If using soaps and detergents, do not use any form of bleach as it can damage the machine.