Of course you can keep spares of everything on your rig all the time, but that gets expensive and you can never out guess what plumbing problem will crop up next. But you can keep a few basics that will keep you going in a pinch.
Use quick connectors and keep some on hand in your rig. Don’t go with the cheap plastic stuff. They strip out too easily.
Keep hose menders on your rig. Again, do not use plastic and also do not use the ones held on by the automotive type band as they not only leak but tend to just let the whole fitting slip off.

Always have either several pieces of soft pliable hose or one long piece. Be sure you have a knife to cut the hose. You want pliable because when you are doing a field fix you do not want to be struggling trying to get a connector on a stiff piece of hose. (My normal hoses are wire reinforced and usually require using a heat gun to soften the end to insert the hose connectors.) These hoses are for down and dirty QUICK fixes.

Sump/transfer self-priming pump
My rig normally uses 3 pumps. The fresh water and grey water pumps are 12V Shurflo type and my bath pump is a fancy sump pump.
Now, some prep has to be considered, especially for the DIY person. Be sure you can open the top of your fresh and grey water tank or at least have a garden hose connecter on the top and bottom of the tanks.
Uses:
1) Drain pump not working
Put sump pump in tub.
Run hose to top of grey water tank or outside Since my bathing system uses a sump pump, I have a hose, with a quick connector, run into my grey water tank. This way I can just remove the nozzle from the bathing system(has a quick connect on it) and attach it to the grey water hose, fire it up and BOOM, water drained.
2) Fresh water pump not working
Connect bottom drain of fresh water tank to transfer pump inlet
Open the fresh water tank drain(Yeah, I forgot this several times and had to drag my sorry butt out to the back of the unit and open the valve)
Connect hose from pump out to water system or directly into tub
3) Bathing system pump not working
Connect short piece of hose to inlet
Connect bathing system output hose to pump out. It may not have as much force as your bather, but it will get you through the day.
Preventative items:
1) Most units use RV type pumps that stop when the water flow stops. Great when it works correctly, but not always!
My Story. I was traveling from one client to another and I stop at the gas station. As I am coming back to the van I see water coming out the back and side doors. I open the back of the van and find that a hose has broken. So, the RV pump did its’ thing and came on. Well that was not good, but, in and of itself, not that bad. What was bad was that the way the van was laid out that water was sucked into my inverter. That was a $1200 design flaw.
THE PREVENTATIVE FIX – I now have switches on those pumps and turn them off and on with the switch so this never happens again.
