Off-grid water works


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Do you know where your water comes from? You probably just turn on the tap and there it is. Flush the toilet and off it goes. Most of us have no idea where our water comes from, or where our sewage goes.

At CAT we do things differently. We’re completely off-grid when it comes to water – we have no mains water supply or sewage treatment. So we have to think very carefully about how we use this precious resource.

Here’s how our water works.

Reduce, reduce, reduce!

compost toilet at CAT
compost toilet at CAT

We start by minimising the volume of water that we use. Low flush toilets, waterless urinals and compost toilets help by reducing the amount that gets flushed away. Low flow taps and water efficient shower heads mean less goes down the drain. Which of these things could you do at home?

So what’s left? We need it for drinking water, for hydro electric turbines and to power our cliff railway. Let’s focus on how we get it clean enough to drink, and how we treat the wastewater so it can be safely returned to the river that flows past CAT.

Good enough to drink

CAT Reservoir
CAT Reservoir

The CAT reservoir, which is nestled in the hills behind the visitor centre, holds most of the water used on site. It was created to directly power the machinery for the old quarry on which CAT is built. The other sources of CAT’s water are rainfall into the lakes, ponds and rainwater butts across the site.

The water is siphoned from the middle of the reservoir, using atmospheric pressure to force it up through a pipe. This method doesn’t use a pump, which ensures that the system is low-energy.

Water is then piped down the hill to CAT. Water to be used for drinking passes through slow sand filters to remove pollutants. While this process effectively removes pathogens, the water is later treated by ultraviolet (UV) purifiers to finish the job.

Filtering the CAT water supply
Filtering the CAT water supply

Managing the wastewater

Greywater and foul water from CAT flows into settlement tanks, where solids are separated from liquids. Solids are composted whilst liquids are passed into a series of reed beds which sit below the CAT site.

Grey Water Tanks
Grey Water Tanks

The reed beds clean the water through a combination of the micro-organisms in the reed beds, and the physical and chemical properties of the reeds.

Reedbeds

After being passed through these beds, the now clean water is returned to the river below CAT, where it is joined by the water that has powered our hydro turbines, driven the cliff railway and heated a building through a water-source heat pump. All of it borrowed – and made to work very hard – on its way from the mountains to the sea.

Over the summer, we’ll be giving free guided tours of the CAT water systems so you can get a close-up look at some of these systems. Take a look at our events calendar for details of what’s on when.

If you’d like more in-depth info, the three courses mentioned above run back-to-back and can be booked as a package. Book two or more of these and we’ll give you 10% off. See courses.cat.org.uk for details, or call us 01654 704966.