Hi, just got this message from my itinerant geriatric gypsy parents, roaming
around somewhere in the north of Oz.  They wanted me to pass this on:
---
The Trakka Camper has two water tanks underneath, filled by a single filler
inlet.  One of the tanks has got a heat-exchange coil inside.  Radiator
water is circulated through that coil to provide hot water for showers etc.
(There are hot & cold water taps in the sink and shower on the back.)
All works fine until there is a small leak in the coil.  Both tanks get
contaminated through the filler/overflow fittings.
We drank boiled contaminated water for several days before realising that
the green colour is not from algae.  (radiator coolant is not so healthy.)
(I added about 2ltres. of water to the radiator in 100km, believing it to be
normal in the heat.)
Eventually it dumped all radiator water into the tank at once, causing
overheating.  We realised immediately and no damage was done.  It happened
on a bush track, 60kms from Cape Leveque, north of Broome.  
A temporary fix, blocking the feeder hoses to the heat exchange with wood
saw us back to Broome - 180kms. 
Anyone with a similar system, be aware of potential problems.
I would:
Isolate the two tanks and have a separate filler system for the hotwater
tank.  You may drink your cold water with peace in your mind. 
Check the colour of the hot water regularly.  If it has the colour of your
radiator water, start cursing.  Its the end of hot showers.  Block off the
radiator hoses that go to your tank.  You may still use the tank to store
water. 
-- Other than this, they report that they're having lots of fun and are
heading for the Mitchel Plateau, then down to Kunnunnurra, some 900kms on
dirt road & tracks. 
Cheerio, 
Gerhard & Susan Dauth, 
via: tim.