Safe drinking water from the rain on your roof — purified by living sand and sunlight alone. No chemicals, no filters to replace, no mains.
1
Your rainwater
roof → water butt → Källa
2
Biosand filter
a living layer of microbes cleans the water
3
Storage tank
a steady, fresh buffer
4
UV reactor
UV-C finishes the job
5
Your glass
Safe water on tap, drinkable from day one — 60–80 litres a day per unit, plenty for a household.
Most systems come in around £1,000 — itemised after your consultation.
Day to day
What it needs, what it does, and where it stops
The living filter — a community of beneficial microbes that settles on the sand, like the life in healthy soil — does the work and gets better with age, while the UV keeps every drop safe from day one — no cartridges, no chemicals, no mains. There's just a light rhythm to it, and a couple of limits worth knowing up front.
The daily rhythm
Each top-up
Pour in settled rainwater. Keep 4–6 cm standing above the sand, and never let it dry out.
Let it rest
Let each fill trickle through, then pause before the next — the living layer needs the breather.
If flow drops
Swirl & skim the top of the sand, scoop the cloudy water, repeat till clear.
Do
Same source. Feed it the same water each time.
Let it settle. Let cloudy water clear before pouring in.
Keep it covered & topped. Lid on; 4–6 cm above the sand.
Covered storage. Store finished water covered, with its own tap.
Don't
Don't overfeed it. Too much water with no rest overwhelms the living layer.
No chemicals. Chlorine or bleach harms the living layer.
Don't move it full, and don't open the UV unit.
Water only. Never run any other liquid through it.
Feed it water you trust
It clears microbes and dirt, not dissolved chemistry — so it can't remove chemicals like glyphosate or metals (we're looking into an optional carbon stage for that). It starts at your roof: collect off inert roofing (avoid lead flashing, asbestos-cement or freshly-painted roofs), keep gutters clear, and keep oils and spills well away — they can ruin the living filter.
❄ Winter & frost — the one UK gotcha
Frost is the one thing to plan for. Keep the filter, tank and UV unit above freezing — an insulated outbuilding, or lag the tank and pipes. A tank, reactor or pipe can crack; a frozen filter simply rebuilds itself over a few weeks (boil or test while it does). Off site in a cold snap? Drain the reactor and exposed pipes first.
Staying safe with your water
We test every UV reactor and pump before it ships, and the tech is field-proven. As every site's rainwater differs, we recommend a simple independent water test on commissioning. Supplying more than your own home? That's a private water supply under UK law — we'll help you meet it.
At a glance
60–80 L
per unit · per day
10+ yrs
filter lifespan
0 chemicals
no mains
Day & Night
solar + battery
How we work — bespoke to your site
1
Consultation
A friendly chat about your site and rainwater — no visit needed — and we design around it.
2
Build & Ship
We build it by hand in the UK and ship only the parts your setup needs.
3
Assembly & Installation
It arrives with clear illustrated instructions. Installation available for a fee.
Most systems come in around £1,000, itemised after your consultation.
Designed & assembled with bare hands in the UK
Corporate sponsorship brings the same system to communities overseas — ask us how.
Källa
SHELL-ahSwedish for source
