Why a 250 litre tank? What about a 175 litre tank?
175 litres of water weighs about the same as 2 large adults - so an estate car would be quite safe enough. Laid flat with battens to stop the tank moving forwards/backwards or sideways, there wouldn't be a problem if you're only using the estate for travelling round town (i.e. 30 mph or less).
You can nip home to re-fill, if necessary. It depends how many houses you intend to do WFP per day.
Get a van when your 'round' warrants it.
If you want to use the estate for longer/FASTER trips - empty the water out.
Mike
exactly, its easy enough to fit eye bolts and secure the tank
for info purposes only, you know the risks with a 250 L in the rear, if in doubt consult a engineer, i take no responsibility for what you do after you read this info
infact if you search hard enough you will find the same size threaded bolts that secure your seat belts with a EYE on the top of them, they are made for securing racing harnesses in track cars, just remove the seatbelt bolt and change for a eye bolt, you allready have 2 built in points
then fit 2 more in the rear ( boot area )
get the strongest you can find, i went overkill and got the top range stuff when i did mine, i think it was Class 12.9