thanks
1.so water supply to RO unit
2.waste outlet pipe to waste drain
3. inlet (pure water) pipe into storage butt tank
4. then either fill barrels from tap at bottom of water storage butt
5. OR use submersion pump dropped into storage tank with normal hose pipe attached and place other end into van tank and pump away to fill the van tank...

Do you need to keep checking the water reading when filling

Forgive me i dont how these units or systems work so unsure how long i can keep producing pure water for once initial reading is suitable...
Thanks