Last week I had the pleasure of visiting the Centre for Alternative Technology in Wales to learn about rainwater harvesting and ecological sewage treatment. The courses were both fun and fascinating and I am still trying to process all the information I have gained (while trying not to spend too much of my spare time thinking about sewage!).
Eco Rainwater and Water Supplies, Thursday 7th April
The focus of the day was covering the ins and outs, advantages and disadvantages of collecting rainwater for re-use in the home and the garden. I was of the expectation that surely all rainwater harvesting was a good thing, keeping water in the ‘loop’ of the system, reducing demand on the mains, with a near urgency due to climate change and over-extraction. However this was turned on its head as the course leaders explored the energy required to actually make a lot of the indoor rainwater harvesting infrastructure, as well as the energy costs involved in pumping it around your house. 
What was a total realisation for me was actually how good the mains services are in terms of efficiency and that if you can use the mains, that it is a good idea to do so and to really challenge whether your situation is appropriate for rainwater harvesting in the home. That said we did explore the components of a rainwater harvesting system, the regulations that need to be complied with and the basic principles behind collecting rainwater.
Looking at water supply, we did explore some of the situations where rainwater harvesting may be appropriate, for example at a real off-grid location like CAT. Grace Crabb, the biologist leading the course, took us on a tour of the site and we walked up to the reservoir to witness where the whole of the site source their water. CAT are lucky to be in such a great location in terms of collecting water from springs, natural run off from the hills as well as having a high amount of rainfall, in a natural reservoir that can gravity feed the rest of the site!
Back in the classroom a key session of the day was on water efficiency, the first port of call in any water system. This is where an individual, family or community are likely to have the greatest impact and we talked through all the gizmos and gadgets on the market, from the simple to the bizarre, that may or may not help your family reduce their water use. In reducing the water you use, its useful to have an understanding of where most of your water is used and what for, toilets is a main one (hence why we all just love compost loos) as well as washing.
Where rainwater harvesting can be of real use however is in the garden. This was my key learning aim from the day as we have so many greenhouses at Brook End and with so much propagation if we can find a way to harvest rainwater or re-use greywater successfully then we are on to a winner. Most people associate greywater harvesting as having a rainwater butt connected to a downpipe, which is a simple but effective system, especially if the butt itself can be made from a waste product or used container. CAT use massive old orange juice tanks and apparently Oxfam sell something similar.
However another back-to-reality moment that was communicated by the tutors was that in areas where rainwater harvesting may actually be needed, for example places where there is unsustainable pressure on the mains (such as the South East of the UK), this is where you are actually unlikely to be able to harvest enough rainwater to support your needs! We did some basic calculations, measuring the surface areas of our roofs and our annual rainfall amounts. The participants from Wales seemed pretty smug as they could easily meet their needs while me in poor old somerset was left with something like 48 litres a day as a tangible amount, when average water use (at the high end) is 180 litres per day per person!
Another interesting point about rainwater is its classification. It is in ‘Fluid category 5′, meaning its treated as a polluted source. We did explore the potentials of what rainwater may have in it, for example all the gases dissolved through traffic and industry, however it is unlikely to be an issue for plants but to get to drinking water quality may be likely to need need treatment.
As with most permaculture systems we need to ‘use what is there’ before making any energy-intensive changes, which to me applies to using the mains if needed and not feeling bad for that or if you’re selling out on a super-closed loop off grid system! Course tutor, Dr Judith Thornton, emphasises that if you’re looking to reduce your carbon or ecological footprint, then go for another area of your life that has more impact, such as food or transport. That said we are always having to respond to environmental changes and how the picture of the UK may look in another 50 years is a different story, rainwater harvesting is also vital in other climates and countries so either way the day provided much useful information and awareness about how to set up a rainwater harvesting system and what the other potential considerations are when deciding water supply routes.
There was a lot more to the day but these were the key points that I took from the course, that is before being bombarded with three days of non-stop conversations about ‘waste management’ of the human bodily function variety!
