Is it better to paint spray with a diaphragm pump or a piston pump?
Diaphragm Pump Pros
Diaphragm pumps are typically lower priced compared to airless pumps. They are often able to deliver higher volumes of fluid, for example this 1.5” diaphragm pump can deliver up to 106 Gallons Per Minute at maximum (though you will typically not want to run the pump at this rate continuously). They are also a bit more compact than airless piston pumps.
Diaphragm Pump Cons
The major downside to diaphragm pumps is that they do not provide much pressure. This means they can be limited in their ability to move material over a given distance or up heights. They will also need to have an alternative way to break material apart rather than pressure (like an air spray gun) if you plan on atomizing coating.
Piston Pump Pros
Piston pumps provide significant pressure to fluid which when fed to an airless spray gun will allow a pattern to be created. This pattern allows for fast application of a coating and is one of the fastest ways to apply coating when compared to air assist airless and air spray guns. Additionally, the high pressure of the pump will allow coating or material to be delivered vertically well or over larger horizontal distance while a common diaphragm pump will often be limited in the distance that the material can be supplied over. An airless pump also comes in electric or gas driven options which make it a good option for job site work.
Piston Pump Cons
The major downside to an airless pump vs a diaphragm pump will be the volume of material that the pump can supply. Common Airless paint sprayers will deliver at most 7 GPM (these are extraordinarily large airless pumps). There are unique airless options that provide material at lower pressure ratios (like 3:1) with higher volumes but can be quite expensive. They are also a bit more expensive to repair as there are potentially more parts that will wear over time.