I don't like to use my home washer for saddle pads (they don't fit in very well and tend to come out only partially clean), so I used to beg my trainer to throw my pad in with hers when she did a load
My barn just installed a washer/dryer, though, so now I can wash them there.
The local laundromat apparently had problems with people putting hairy saddle pads in the machines and now prohibit using their machines for horsey things
I just wash them in the washer like I would anything else and then hang dry.