Hi Paula,

Chlorine is not only agains the smell but more importent to avoid legionnairs disease. If you are only for a few weeks in Spain it seems useless to use chlorine in the whole cisterna. If you want to do it controlled then buy yourself a watercube, pump the water you will use in the cube. You can then put chlorine only in the water in the cube. In most big supermarkets you can buy chlorine for swimming pools and also test strips to find out if you did enough chlorine in the water.

Good luck,
Mark