French Drains can utilize several types and sizes of French Drain Pipe. An older type that is not commonly used any more is 4 inch PVC Pipe with large half inch holes drilled in the Pipe. This doesn't work very well, Because the holes are too large and the number of holes in the French Drain Pipe are too few. Also there is no filter or "Soc" around this particular French Drain Pipe. If it is used in sandy or loose soil the holes will clog and the pipe will fill up with sand. PVC French Drain Pipe should be avoided.
ADS French Drain Pipe is much better, the holes are smaller and much more numerous. It also comes inside a soc that acts as a filter and helps keep sand and debris out of the French Drain Pipe. It works very well.
For Small business and Residential French Drains, Four inch ADS Perf/Soc French Drain pipe is adequate and the most common. It is used for the majority of all French Drains installed. French Drains can be installed using 3 inch ADS Perf/Soc but many times it is too small and can be overwhelmed by a heavy rain or from a bad design. (Too many gutter down spouts connected directly into the French Drain, For Example) Three Inch French Drain Pipe should be avoided if possible.
Six inch ADS Perf/Soc French Drain Pipe is usually a good idea when possible. It carries a much larger volume of water. Six Inch French Drains are rarely overwhelmed.