Cost factors of installing a rain water harvesting system

It’s inevitable that mains water will be eventually charged to domestic consumers in Ireland. Let’s assume that the charges will be high enough to justify installing a rain water harvesting system over a period of 25 years. The following measures would help to lower and to justify the cost for the fully installed rainwater harvesting system:

• A simpler system of using rain water for toilets only, using just fine filtering would be cheaper to install and operate than also using ultra violet lights to actually further treat the water for drinking.
• Having smaller storage tanks inside the building will avoid digging a large hole in garden for a big storage tank. It will also avoid the often unforeseen additional installation costs and the repair costs to the garden.
• Shorter pipe runs for the rain water system will reduce the cost for the pipes themselves. By planning the length and the route of the rain water pipes to be as direct or as short as possible will result in an installed cost saving.
• Collecting rainwater from 2 to 4 down pipes at the corners of a house may involve the cost of digging up footpaths. Compromises will often be made to collect water from one down pipe only; but this greatly reduces the volume of rain water that can be collected. It would be best to collect water from all the down pipes without involving all this construction work at ground level. Perhaps the rain water pipes can come directly across the house through the attic?
• The collecting and the storing of the rainwater at a higher level in the building will reduce the energy used by the pumps. Lower pumping costs will keep the running costs low over the 25 years of operation. The pump is likely to operate for longer lifetime if it uses less energy. Ideally a system that uses gravity alone, that does not require a pump at all will be more environmentally justifiable and reliable.