Water Re-use – systems for Greywater
What is greywater, as opposed to rainwater harvesting? Basically it is water that has been used once, hence the term recycling. In short ‘greywater’ (which can also be spelt ‘grey water’) describes water that has been used in showers, baths and washing machines. Use of it is more restricted than rainwater, as it will contain some chemical and biological contaminants. It can never be used as drinking water for this reason.
Uses for greywater
Irrigation (plant watering) is the main safe use for greywater, and it can be used untreated within 24 hours, but should not be used on food crops. It is OK for use on landscaping (lawns, etc), flower gardens and trees. One caveat is that it shouldn’t be used in a sprinkler system due to the possibility of people inhaling potentially contaminated water droplets.
The other main use for greywater is for toilet flushing, but for this it does have to be filtered or treated first. It is ideal in a commercial environment as it is likely that toilets will be used more frequently which keeps the water moving through the system. It is recommended that the water be at least filtered first, to avoid clogging up pipework.
It is a good option for hotels, leisure centres and larger commercial (office) premises. It would be possible, using greywater for toilet flushing, to potentially save at least a third of the total water usage.
How is it recycled?
It would normally be collected by a plumbed in diverter from a washing machine, bath or shower waste outlet and sent to a tank, via pumps or gravity. This is because greywater will contain organic and chemical substances which can cause bacterial degradation and be in themselves pollutants.
If it can’t be used straightaway, then it will need to be treated first.
The treatment involves filtration to remove particles, then biological and/or chemical action to remove harmful bacteria and viruses.
Types of tanks
Header tanks are small, usually rectangular, water tanks to be installed in loft areas, where the water feed can use the power of gravity alone to full up toilet cisterns. Tanks-UK have a variety of small tanks suitable for this purpose.
Underground water storage tanks – we can supply smaller capacity plastic tanks for underground water storage, or larger GRP ones.
Water treatment systems – Tanks-UK supply the Harlequin water treatment systems which can effectively be used for greywater as well as for sewage.
Legal Requirements
Anywhere there is a possibility of contact with the mains water supply, for instance, if a header tank is used, and a mains top-up provided, you will need an AB (air break) point to ensure there cannot be any backflow into the mains clean water system. Underground tanks may also need them.
WRAS (Water Regulations Advisory Scheme) have a useful booklet available to download. Here is the link: https://cdn.shopify.com/s/files/1/0829/4323/files/Water_reg_Advisory_note_09_02_04.pdf?v=1629302045
Greywater pumps, filters and pipework
Tanks-UK supply the DAB range of pumps and for greywater we would recommend the Nova pumps as the most suitable. As durable submersible pumps with stainless steel components and a polymer exterior they will give years of service, and we stock them in several sizes.
Tanks-UK can advise you on the best filters to use, and we also supply the pipework and fittings to complete a system.
Just give us a call on 01953 665940 or email info@tanks-uk.com with your requirements and we’ll send you a quote.