When it comes to surface cleaning bigger is not always better. The size of the surface cleaner depends on how many gallons per minute your pressure washer has. The general rule for a surface cleaner is for every 1 gallon of pressurized water equal 4 inches of surface cleaning diameter. For example a 4 gallon per minute approximately 2800 psi pressure washer can use a 16 inch pressure washer. Please note this does not mean you will be able to push the surface cleaner around quickly for a more efficient clean but instead you will have to move in a pattern and slowly so the spinning turbine can clean the flat materials pores well enough.
If you choose to move faster with your surface cleaner to get a faster clean in less time we suggest you move up in gallons per minute on your pressure washer or cut down on the surface cleaners diameter. a reasonable size pressure washer and surface cleaner to use for getting an efficient clean is an 8 gpm and a 28 inch big guy surface cleaner.
For larger surface cleaners we think it is best to use primarily on commercial plazas such as shopping centers, gas stations and parking lots where there is a big amount of square footage, typically in the 36 inch to the 48 inch range
For small or medium residential cleaning tasks a size like the 19 inch whisper wash and 28 inch surface cleaner for a large enough cleaning but still managable to move around from house the house.