Collecting rainwater cuts mains water use and bills, and it is ideal for flushing toilets, washing machines, gardens and vehicle washing. But rainwater picks up dust, leaves, bird droppings and bacteria from the roof on its way to the tank, so it needs the right filtration for how you plan to use it, and the system must be kept completely separate from your drinking water.
At a glance
- Typical issues: leaves and debris, fine sediment, bacteria from bird and animal droppings, slight acidity
- Water regulations status: rainwater is treated as fluid category 5, a serious health hazard
- Typical treatment: gutter and tank inlet filtration, then a self-cleaning filter on the pump outlet; add UV for higher-grade uses
What can rainwater be used for?
| Use | Treatment typically needed |
| Garden watering and irrigation | Inlet filter on the tank; a coarse filter to protect drippers and sprinklers |
| Toilet flushing and urinals | Inlet filtration plus a fine self-cleaning filter after the pump |
| Washing machines | As for toilets, with good fine filtration; many systems add UV |
| Vehicle and yard washing | Coarse and fine filtration to protect pressure washers |
| Drinking, cooking and bathing | Full private supply treatment: staged sediment filtration, pH correction, UV disinfection, regular testing. Seek advice first |
How rainwater filtration works
- First-flush and gutter filters divert or catch the dirtiest early run-off and leaves.
- Tank inlet filter removes debris before water enters storage. A calmed inlet and floating suction draw the cleanest water from just below the surface.
- Self-cleaning filter after the pump catches fine particles before they reach toilet valves, washing machines or irrigation. Our Hydra self-cleaning filters, such as the Hydra Rainmaster Trio and Hydra RAH with 90 micron stainless steel screen, can be flushed clean without removing the element.
- Finer filtration and UV where water quality really matters. Use sediment cartridges to protect the UV unit, then UV disinfection to control bacteria.
Water regulations for rainwater systems
Because rainwater can contain pathogens from animal droppings, it is classed as fluid category 5 under the water fittings regulations. According to the Water Regulations UK guide to alternative water systems:
- No cross-connection. A rainwater system must never be connected directly to mains water pipework.
- Mains top-up needs an air gap. Where mains water tops up the rainwater tank, it must be protected by a type AA, AB or AD air gap, or a type DC pipe interrupter.
- Label everything. Pipework and outlets carrying rainwater must be marked in line with BS 1710:2014 so nobody mistakes them for drinking water. See our BS 1710 guide.
- Notify first. You must notify your water supplier before installing plumbing for an alternative water supply, even when an approved contractor does the work. See regulation 5 of the Water Supply (Water Fittings) Regulations 1999.
If rainwater is ever used for drinking, it becomes a private water supply and must meet drinking water standards under the Private Water Supplies (England) Regulations 2016.
Maintenance
- Clear gutters and inlet filters regularly, especially in autumn.
- Flush self-cleaning filters when the pressure drop rises; with Hydra units this takes seconds.
- Inspect the tank for sludge build-up and clean it out periodically.
- Replace UV lamps every 12 months if fitted.
Related pages
Why Wrekin Water
Wrekin Water is a family run company based in Bettisfield, Shropshire, serving more than 50,000 customers over 15 years and rated Excellent on Trustpilot. We supply rainwater filtration, sediment filters and UV systems, and can help you choose the right setup for how you will use the water. Ask our team.