First, what exactly is greywater? Well, it isn’t the same as rainwater because it has already 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 – it is never potable (drinkable) but it can be re-used for some purposes.

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. However, untreated it must be used for irrigation purposes within 24 hours, so a holding tank without some form of treatment is probably not an option, unlike rainwater storage tanks. This is because greywater will contain organic and chemical substances which can cause bacterial degradation and be in themselves pollutants. However, the water is sufficiently clean to be able to irrigate landscaping, flower gardens and trees – but not food crops, because there is a chance they could absorb chemical or other harmful pollutants as well as nutrients.

The other main use for greywater is for toilet flushing, but for this it does have to be filtered or treated first.

The treatment involves filtration to remove particles, then biological and/or chemical action to remove harmful bacteria and viruses.


In domestic applications, greywater recycling is a good way to reduce overall water usage and do your bit for the wider environment in reducing overall water consumption.

This could be a simple system of short term storage and recycling, or a treatment system such as a septic tank for longer term storage, e.g. for toilet flushing, irrigation use in dry weather or times of drought.

172105 1250 Litre (270 gal) Vertical Non-Potable Water Tank Enduramaxx, Enduratank, Rainwater Tanks, Industrial Water Tanks, Non-Potable Water Tanks, Vertical Water Tanks

There is a new Enduramaxx underground tank which would be suitable for domestic (single dwelling) use, being 1500 litres capacity. Above ground tanks are also an option, especially for short term irrigation use with no treatment other than filtration. Tanks-UK supply a whole range of above ground vertical or horizontal tanks suitable for this purpose.


Greywater recycling is a good option for hotels, leisure centres and larger commercial (office) premises. It would primarily be used for toilet flushing in commercial establishments, as this is one of the highest volumetric uses of water in this context. It is possible to potentially save at least a third of the total water usage.

For businesses greywater recycling can contribute to carbon reduction and overall sustainability targets.

Obviously underground water tanks are a good idea to save on ground space on commercial sites, for instance they can be installed below landscaping areas. The larger underground water tanks can be used either as treatment tanks, or for storage post-treatment. Enduramaxx have recently expanded their range to include 5000 and 10,000 litre underground tanks. But for a heavy duty long term durable solution, why not take a look at the SPEL range, for instance the 17,000 litre 300 series, which are rotationally moulded from GRP.

34000 litre underground tank with custom turrets

Gravity feed or pumped?

This will depend on the means of collection and the use to which the greywater is put. For direct garden irrigation, it may be possible to use just gravity feed to the tank and onwards below ground directly to the soil beneath the plants.

For recycling by toilet flushing, it will be necessary to use a pumped system to return the water to the toilet, or to a header tank. Note that the header tank will have to be separate from the mains water supply or you will need an AB (air break) point to ensure there cannot be any backflow into the mains clean water system.

Greywater pumps

Nova 600 MA


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.

Filters and pipeworkRainwater Filters and Accessories,3P Technik,

These systems will obviously involve pipework, valves and filters, all of which Tanks-UK can supply.

Just give us a call on 01953 665940 or email info@tanks-uk.com with your requirements and we’ll send you a quote.

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