Drains
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I recommend using PVC (duh!) for all drain work. It is easy to make up systems for drains and vent pipes, and is freeze-resistant (but not freeze-PROOF). ALWAYS use a good primer and glue as required for your plumbing connections. The primer cleans the fittings so that they won't break or pull apart when stress is applied. Colored primers are proof that the connection is indeed clean and ready for assembly. Make square cuts, and always deburr the ends. That piece of crap you forgot to take off can and WILL attract debris, leading to a clog at the worst of times.
Also, make sure that there is sufficient pitch on the pipes to allow drainage. If you're camped on a slope, there may not be enough pitch in some drain systems to allow easy drainage to the tank(s). While a pitch of 1/8th inch per foot is a minimum for houses, they don't move around! (or shouldn't, anyway). MORE pitch is OK! Keep your runs as short as is feasable, to reduce costs for materials and complications in assembly. Remember to add cleanouts (screwed caps or plugs) to the system, just like house plumbing. Sooner or later you will clog a drain, and will want to get at it fairly easily to fix the problem.
Always use a P-trap from the sink(s) and shower/tub. This will prevent smelly gases from the black and grey tanks from entering the bus. The water at the bottom of the trap provides an andequate and effective barrier to the stink.
You WILL need to have a vent pipe sticking out of the roof, or at least high on the side of the bus. This acts as a vacuum breaker when you drain the sink, flush the toilet, etc. It allows the fluids to drain readily into the appropriate tank(s). The vent pipe is attached to the drain system, essentially rising up directly from the main drain line to the black/grey water tanks. There are vent stack 'boots' made of galvy steel/rubber, aluminum/rubber, or just rubber that will provide a good seal, and keep weather out of your ceiling and walls. Follow directions on installing them, and use a good flexible sealant when attaching it to the roof. Use rust-proof fasteners, I recommend stainless steel ones. A couple stainless screws won't bankrupt you...
PVC drains can be insulated if need be, there is foam plastic/foam rubber insulation for drains, and even rigid fibreglas insulation is available. Most hardware stores/home centers will NOT have the sizes you may want, so look up "Insulation" in the Yellow Pages or internet. Be aware that they usually have a 'no return' policy, so measure carefully for the diameters, thicknesses and lengths you need. They also have available special covers for elbows, tees, etc. Just ask.
The flexible drain connections are great, as they save having to do a precise job installing the P-trap to drain connection. Makes sink installs a LOT easier.
If you can't run a vent pipe directly from the sink (if the sink is too far from the main drain, for example), you can install a vacuum breaker for your sink, just follow directions that come with it or you WILL have nasty stuff back up in your sink pipes!
I've seen folks take a copper kitchen bowl, cut a hole in the bottom for a drain (have a drain handy when doing this), decorate it with hammer marks with a ball peen hammer and a sandbag for support, then install it. One drawback is the need to keep it well polished, a pain in the butt IMHO.
I've done custom fibreglas shower bases, I find that it's best to work with a plaster "master" pattern. Start with a wood frame, and build up the plaster on it to make a male of the shape you want. The more attention to detail and quality of finish you place in it, the better the work will come out. Easier to finish plaster that it is to grind fibreglas and refinish it
When the plaster is thoroughly dry, shellac and wax it. This will make it easier to get the finished fibreglas part off. I use Butcher's Paste Bowling Alley Wax, does wonders. If the fibreglas/epoxy manufacturers recommend a specific mold release, USE IT.
And one other thing: DON'T MAKE THE MOLD WITH NEGATIVE DRAFT!!! If ya can't get the mold and part separated, what's the point in making it?
Some places that can weld up water tanks from plastic can also make shower pans, be aware they may be VERY slippery when wet.
IIRC, RV drains are on the LEFT (drivers side) of the Bus?
