What size pipe to drain parking area

[fiddler]

I need to drain a 130m2 stone/gravel parking area and the run off from a 24m long sloping driveway. The ground is nasty clay; can I get away with 4” perforated twin wall or should I use 6”?

Thanks

 

[Lincs Lass]

Future proof and use 6''

 

[Zebbedee]

The price difference between 4” and 6” twinwall is nothing so use 6”