Light Duty Residential:
Is an axial radial pump with steel pistons. The shaft can be vertical or horizontal with a built-in internal bypass unloader valve. These are generally non-serviceable (no oil changes) and have an aluminium pump head. Recommended for residential use like the patio furniture and car and perhaps the siding and gutters on a small building once per year. Large areas will take a lot of time to clean and it will be hard to clean walkways without streaks.
Light Duty Commercial:
Is an axial radial or triplex pump with steel pistons and a built-in internal bypass unloader valve. The oil end is serviceable (you can change the oil) and they are built with a strong brass pump head. Recommended for more frequent residential work and light commercial jobs. The PSI and GPM of these pump can be as high as many industrial pumps but without the ceramic pistons and external bypass these pumps are not meant for the heavy commercial user.
Is a triplex pump with ceramic pistons and a built-in internal bypass unloader valve. Repair kits are available for the wear items and oil changes are made easy with a drain plug and sight glass. The internal bypass unloader is not recommended for continuous use in a car wash or full time pressure washing rig but a landscaper or painter can be confident the pump will perform well and for many hours of service.
Industrial Duty (Belt/Gear/PTO):
Is a triplex pump with ceramic pistons and an external bypass unloader valve. Built for continuous use in car and fleet wash applications and full time pressure washing. Many drive options as well as pressure and flow combinations are available from misting 0.5 gpm to high flow 20+ gpm and pressure greater than 7000 psi. If your business counts on a pump or pressure washer than you don't want anything other than industrial duty.