The Water Tank
   Hollandse versie

We have a large (approximate capacity 17000litres) underground rain water tank. It is fed from the roof of the house, conservatory, garage and glasshouse via an underground gravel and sand filter. This was the original water supply for the house until mains water was became available in about 1953. Over the years the iron grating at the bottom of the filter had become rusted and broken and  the water was becoming increasingly dirty. We pump the water by hand and an electric pump and use it mainly to water the plants and garden. In August 1999 we cleaned and renovated the tank and the filter. Since then we have installed an automatic electric pump and connected this to the house to supply cold water to the utility room, washing machine, and downstairs toilet representing around two thirds of our water usage. Only on rare occasions has the tank run dry. The longest period was two weeks. We save a couple of hundred pounds each year in the cost of.water and the cost of the pump etc has paid for itself many times over. Now in 2010 it is still providing clear clean water having required no maintainence to date.

Click on the pictures to enlarge.
The filter pit showing the outlet to the tank. One of the inlets can be seen top left.
Stainless steel drum from an old washing machine. The drum was placed over the outlet to prevent the gravel from entering it. First a layer of coarse gravel was used to cover the drum followed by a layer of finer gravel to retain the sand.
A thick layer of sand was used to cover the gravel. A further layer of fine gravel followed by a layer af coarse gravel finished the filter. Access to the tank is via a small manhole. The floor of the tank is about 10ft below ground level. Despite the temperature above ground of 34degrees it remained cool.
The  inlet pipe to the tank from the filter and the lead pipe (left) leading up to the pump The ladder used to get down into the tank. The tank  is 12ft x 7ft x 8ft high.  The roof is an arched construction made of brick. Although the screed needed some attention the 100 year old brickwork is still in excellent condition. Black sludge (not smelly!), from possibly 100years of use, was pumped and bucketed out of the tank and deposited on the garden.

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