permaculture

["Dominic & Helen Dring" <thedrings@telefonica.net>]

We have a 3 hectare smallholding in Southern Spain and need a swimming pool.
We are in the process of completing 2 rental apartments and, while I am keen
to create a swimming lake in the future, would like to build a simple pool
which could double as a holding tank for water pumped from our well.
Can anyone point me towards a design / system that would be cost-effective;
as chlorine free as poss.; and act as a holding tank for non-potable
domestic water (we are on mains electricity but have occasional cuts which
currently leave us without pumped water).  We are served with irrigation
water through the summer so I can't see a great deal of benefit using the
pool as an irriation/watering source.
Many thanks.
Dominic