Build It Magazine November 2016 edition - Freeflush Rainwater Harvesting Contribution
"Often a key driver behind rainwater harvesting is environmental benefit and a desire to reduce mains water usage. Many people considering rainwater harvesting understand the environmental and financial cost in the production of potable water and also realise the wastefulness of flushing typically 30% of mains water down the toilet.
BS 8515:2009 is a good start to understand the principles of rainwater harvesting; design, installation, water quality and maintenance. Technical and economic feasibility is essential to understand whether a system is viable. The design component should involve an assessment of supply and demand and ideally consideration of local time series rainfall to optimise the storage requirements. Many domestic systems have moved towards a shallow tank system allowing swift installation and reduced contractor risk. Consideration of all the filtrations steps is essential to maintain good water quality which in turn should reduce the incidence of any unplanned maintenance. However any system with mechanical components will require maintenance and this should be borne in mind from the outset.
Aside from the obvious cost-benefit of any system there are side benefits which are as yet still evolving and unmeasured. Rainwater harvesting systems effectively provide onsite storage and so act as storm relief something which water companies have been battling with for many years to reduce combined sewer overflows. Conventionally this has been addressed with large concrete tanks at significant cost, perhaps smaller scale rainwater harvesting is a tangible alternative with greater benefits.
Finally, it's worth noting that 15% of river catchments in England and Wales are classed as "over abstracted" and 18% as "over licensed. Rainwater harvesting offers an alternative to truly managing our natural resources in a more sustainable manner"
- free flush