If you mean the black pipe, its John Guest pipe/fittings you need. Mark I have an 18.57-5 so I presume you will be putting it under where the TV normally goes? I find the best place to buy the fittings is at the larger caravan parts place or on line. To be honest I have never seen that pipe at our Bunnings. If you want some photos of a factory fitted one send me a message. You also have to do the drain

. We used our washing machine on the weekend and it was great, but then we had to pay $6 to dry our washing. $6!! I thought that was a bit expensive. Our installation has the tap inside in a tiny cupboard next to the washing machine, I think it could be done with the tap underneath, I would be interested if the new ones (Like Rens) are done any different.
Photos on Page 2.
http://www.expandasdownunder.com/threads/maccas-2012-18-57-5.5035/page-2