Rainwater harvesting tanks

For domestic properties, “greywater” uses (toilet flushing, laundry, and garden watering) account for around 50% of total household water consumption. By replacing metered mains water with harvested rainwater for these applications, users can reduce their water bills significantly. For agricultural and commercial sites with large roof capture areas, payback periods can be even faster due to higher daily volume requirements.

Read our full Buyer’s Guide to Rainwater Harvesting for a breakdown of calculating roof size vs. tank capacity.

No. Harvested rainwater is classified as non-potable water. While it is ideal for gardening, crop spraying, vehicle washing, livestock washdowns, and flushing toilets, it is not safe for human consumption without specialised UV sterilisation and heavy multi-stage filtration systems.

Rainwater is naturally soft, mildly acidic, and free from the treatment chemicals (such as chlorine and fluoride) present in mains tap water. Because it contains organic compounds that act as natural fertiliser, rainwater promotes healthier plant growth. Additionally, its soft water profile prevents limescale buildup and reduces the amount of soap or detergent needed for commercial vehicle and site washing.

A complete above-ground rainwater system generally consists of four primary components:

1. Rainwater Filter / Diverter: Connects to your downpipe to screen out leaves and debris before water enters the tank.

2. Calmed Inlet: Directs incoming water to the bottom of the tank without stirring up settled sediment, helping oxygenate the water to prevent stagnation.

3. Overflow Siphon: Skims off floating debris (like pollen) and channels excess water away when the tank is full.

4. Submersible Pump: Delivers pressurised water from the tank to your hose, washdown point, or greywater system.

Tank size depends on two factors: your roof catchment area (m²) and your intended water usage. As a general rule of thumb, every 1m² of roof area captures around 0.8 litres of water for every 1mm of rainfall. Tuffa manufactures single-unit plastic tanks ranging from 1,350 to 20,000 litres, and multiple tanks can be easily interlinked to achieve even larger capacities for commercial and agricultural sites.

Yes. Tuffa plastic water tanks are designed to be interlinked using our heavy-duty tank linking kits (available in 1″, 2″, 3″, or 4″ pipe sizes). This allows you to expand your total storage capacity up to tens of thousands of litres as your site demands grow without requiring custom bespoke manufacturing.

In a domestic setting rainwater can be used for flushing toilets, washing machines and outside use including gardening. These applications account for around 50% of total water use.

Find out more about rainwater harvesting including it’s benefits and the types of tanks available in our expert guide to water tanks. 

A rainwater harvesting system consists of a tank, filter and a pump where required. The costs of a tank ranges from around £350 to £2,000. A basic filter & diverter costs around £50 whereas a full kit including overflow siphon and calmed inlet costs between £300 to £800 depending upon the roof size. Where required a pump costs between £550 to £900 depending upon the size of the tank and whether mains top-up is required. Based on these calculations a full rainwater harvesting system costs between £400 to £3,500.

If you are on a water meter then rainwater harvesting can save you around 50% of your domestic bill (around £215 annually) or up to around 85% on your commercial and agricultural bill.

Find out more about rainwater harvesting including it’s benefits and the types of tanks available in our expert guide to rainwater harvesting. 

Yes, according to Fresh Water Habitats fish and other wildlife prefer untreated rainwater which contains fewer chemicals and chlorine. Rainwater harvesting is a great solution for ponds which require regular top-ups.