Design distribution: dual systems, backflow and freeze protection
Pipes carry the water from treatment to taps. Keeping untreated water out of drinking pipes and keeping pipes from freezing are the two big design jobs.
How
- If you use untreated rainwater or other non-potable water for toilets, laundry or garden, run it in fully separate pipes. CDC advises keeping rainwater separate from piped drinking water so it cannot enter those pipes.
- Label non-potable pipes and taps clearly. Follow your local plumbing code for colour and backflow devices.
- Keep buried water pipes away from septic and sewer pipes, and use pipes rated for drinking water contact (enHealth cites AS/NZS 4020 as the Australian example).
- In freezing climates, bury lines below your local frost depth (ask your building authority), insulate exposed pipes and pumps, and add drain-down points. Frost depth varies widely, for example: England and Wales (UK) water fittings guidance asks for 750 mm to 1,350 mm of cover; Minnesota (USA) building rules use 42 inches (1.07 m) in the south of the state and 60 inches (1.5 m) in the north for footings.
- Fit isolation valves on each branch so leaks can be found and fixed without draining everything.
- Flush metal pipes that have stood overnight; an NSW Health study cited by enHealth found three minutes of flushing removed the problem in most cases.
- Flush little-used taps, showerheads and dead legs at least weekly (HSE, CDC). See thermal-23 for hot water storage temperatures.
Do these first
Sources
- Collecting Rainwater and Your Health: An Overview. US Centers for Disease Control and Prevention (CDC), accessed 2026-11
- enHealth Guidance on the use of rainwater tanks. enHealth, Australian Government, accessed 2026-11
- How should below ground pipework be installed?. Water Regulations UK (WRAS), accessed 2026-11
- Minn. R. 1303.1600 Footing depth for frost protection. Legal Information Institute, Cornell Law School (Minnesota Administrative Rules), accessed 2026-11
- Managing legionella in hot and cold water systems. UK Health and Safety Executive, accessed 2026-11
- Legionella control toolkit: potable water systems module. US Centers for Disease Control and Prevention (CDC), accessed 2026-11