PUMPS, WASTE MANAGEMENT & WATER TREATMENT From woodworms to water harvesting…
A twist of fate turned a couple into rainwater harvesting champions
L
ittle did Michael and Marilyn Rowe know that allowing for more head room in the woodworm- infested “attic” of their new home would
turn them into rainwater harvesting devotees. But that’s exactly what
happened when the water run-off of part of their new, more steeply pitched roof became an issue with the local authorities. The design of the new roof over the garage ruled out using the existing soakaway on the uphill side of the house so they wanted to install a new soakaway in the small garden downhill. Unfortunately, building
regulations now require the soakaway to be 5m from the house as well as 5m from the highway … and there wasn’t the space to do this. Furthermore, South West Water did not want them to make a new connection for surface water run-off into the main drain.
That’s when the architectural technician responsible for the drawings of their renovation project stepped in and suggested a rainwater harvesting tank from Graf UK, and 12 years later it’s become such an fundamental part of their life that they will be having another, larger one installed in their next home. The former electronics engineer and radio presenter downsized from a 6,000ft2 house in Buckinghamshire, to what is now a 4,000ft2 1950’s house on a cliffside near Looe in Cornwall when their children left home. It was meant to be a relatively minor renovation project but when the chimney collapsed, and all they were left with was a floor and two walls, it turned into a major rebuild. They incorporated extra-thick insulation and solar panels, and it now warrants a B+ EPC rating … but they had not considered rainwater harvesting as an energy-saving measure.
The 2,700-litre Carat tank is now
discreetly installed underground in the garden next to their garage, with the automatic pump inside it, which was only recently replaced after more than 10 years, connecting to three taps spread around the property.
Michael said: “The tap on the
garden shed is approximately 10m above the tank but the pump has no problem in providing good water pressure, even to this height.” The retired couple use the rainwater for watering their 1/3- acre garden, topping up their garden pond, washing their car and pressure washing the decking around their home, which was rebuilt with the living accommodation on the first floor, to command a better view of the sea. Although they do not have an automatic watering system, the pump that comes as standard with the Carat tank switches on automatically when a tap is turned on, enabling Marilyn to water the garden with a hose relatively easily.
Even though the tank is only
receiving the rainwater run-off from the roof above the garage of their 4,000ft2 home (approximately one third of the total roof area), they rarely have to resort to using tap water for these purposes, even during what has been the hottest summer on record.
At the other end of the spectrum, to cater for any excess water accumulating in the tank, an overflow in it connects to a series of infiltration modules which run underground to the lower garden. Even though these are located closer to the house and road than would normally be permitted by Building Regulations, the inspector allowed them because they spread the excess water out over a much wider area than a traditional soakaway.
“Both of us have an aversion to wasting things. I don’t know if it’s our age” said Michael. “Installing a rainwater harvesting system was
initially just a practical solution to a regulatory problem. It was later that we realised the full benefit of having water available for watering the vegetable patch, washing the car, cleaning the drive etc. It has proved to be an elegant solution and so invaluable. We are now total converts and shall certainly be installing one in our next house. You don’t need a huge amount of space.” Their next house, which they hope to move into in the autumn, is an old farmhouse on the edge of Dartmoor National Park, with three acres of well-stocked gardens, a large pond and a paddock to keep keen gardener Marilyn happy. It already features a couple of water butts but Marilyn’s plans to up the ante on the home- grown front means they are looking at also upping the size of their rainwater harvesting tank. So, it’s just as well that the lightweight Carat tanks, which are manufactured from 100% recycled plastic, range in size from 16,000 to 122,000 litres.
“It isn’t about the cost,” said Michael. “Water doesn’t cost the huge amount that electricity or gas does, it’s just the idea of wasting something which is dropping from the sky. Should
30 BUILDING SERVICES & ENVIRONMENTAL ENGINEER OCTOBER 2022
anyone be considering doing this, and it is a new building, I would encourage them to look at the full greywater system, where among other things, you can flush your toilets with re-used water. “Had we known about these systems before starting the design, we would have adapted the plumbing in the house to maximise the use of waste water and installed a full, grey water system but we were too late to do this. Our compromise during periods of very dry weather is to syphon off bathwater manually into the gully in the steps leading up to the house. This is there to collect water from the large, hard surface by the front door and discharges it into the Graf tank, but it also provides a convenient discharge point for the bathwater.” He added: “We are delighted to share our experiences. When we are showing potential buyers around the house their eyes light up when we tell them about the rainwater harvesting system. “Marilyn says it’s making nature do the work.”
As well as a bigger rainwater harvesting system, Michael and Marilyn are considering a wastewater management system for their new home in Dartmoor.
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