Can you drain a washing machine (only) with 1 1/2'' pvc , my inspector says it must be 2'' ?

Code says laundry machine has a load value of 2(DFU) and a 1 1/2 pipe has a load rating of three so why a 2 inch pipe ?

 

Many newer washers pump the water out faster, so hence the code thing. 1.5 may or may not work OK with your washer.

 

Clothes washers are normally rated at 3 DFU each. Clothes washers in a battery of three or more are rated at 6 fixture units when sizing the common horizontal and vertical waste pipe sizing to take into account the possibility of simultaneous discharge and the suds producing effect in the drainage piping.

A 1&1/2 inch pipe is rated at 2 DFU vertical and 1 DFU horizontal.

A fixture unit is a numerical load factor which measures on some select scale the load-producing effects of a single plumbing fixture of a given kind.