Chris,
A kerosene / diesel type burner, these will keep up with the pressures used. You do not need to rely on heat as chemical and agitation will do the job, plus dwell time. There are some tiles that you will not want to use high pressure on as it will cause damage. Your best bet would be to go on a good hard floor cleaning course. Acid type cleaners will etch calcium based tiles etc.
Geoff,
Normally you would connect up to the customers tap, auto fill / auto dump so should not be a problem.