Watering the garden -
a composting  toilet, grey water, rainwater and a bore

The plan

• to collect as much rainwater in tanks as possible
• to separate toilet waste from the grey water
• to use a water free composting toilet
• to re-use the grey water from the house to water the garden
• to have a water bore drilled, if that becomes necessary and is possible

Our first years: the reality

• we collect rain water in three tanks : 1 x 24,000 fed from the roof of the house, 2 x 9,000l fed from the roof of the shed. Over the first three years all tanks were only once filled completely. We would need a larger roof area to improve that result. The current roof area totals 174 m2 (house: 120m2, shed: 54m2)
• we installed a rota-loo composting toilet which does not need any water and keeps toilet waste separate from the grey water
• council requirement is the installation of a conventional septic system for the grey water. We put such a system in and the grey water is treated in the system. We collected it in a separate tank and used it through a separate pressure pump and waterlines to irrigate the garden. We take great care to use grey water friendly shampoos, detergents, and dishwashing liquids in small quantities to keep the grey water as clean as possible. We would like to build a proper grey water treatment system with reed beds and gravel filters. We can't do it at this stage, as it would not be council approved. The bylaws in regard to grey water treatment are changing, though, because of the drought experienced in many parts of Australia. 

left: a 24,000l tank collects the rainwater from the house (roof area 120m2). The small 6,000l tank in the front is our irrigation tank. During the first years we pumped treated grey water into it, now it is filled with bore water. right: two 9,000l tanks are fed from the shed (roof area 54m2). Due to the shape of this roof and the direction of the prevailing winds, this roof collects a lot less water than it should (in proportion to its size).

Enough water?!

Over the summer September 2006 to April 2007 we did not use any freshwater for irrigation purposes at all. We always had just enough grey water. But it soon became clear to us, that grey water alone would not be sufficient for our gardens in the future. We planted a second orchard, established the large vegie garden at the other side of the winter creek and extended the original orchard. That just about doubled the area which needed watering in summer. We contacted a drilling contractor and had a bore drilled in January 2008. The bore has a flow rate of 6000 litres per hour at a depth of 50 metres. Water quality is very good. We now only use bore water for irrigation.  

January 10th, 2008: do we believe in dowsing? Not really, but the drilling contractor insisted! So we had the old bloke with the wishbone here. He found a "couple of streams" underground, and that is where we drilled. We struck water at thirty metres but continued down to 52 metres: 6000 litres per hour, very good quality. The question remains: if we drilled anywhere else, would the results be different? Or was this the only spot with a "couple of streams?" Anyway, we were very happy with the result!

Some thoughts about suburbia and water for the garden

Water supply for suburban areas is a huge problem in Australia. Let's compare our situation here -before the bore was drilled- with suburbia. In Townsville our town water allocation was 775kl/year, and we used it all. Here in Tasmania we collect rainwater on a roof area of  174m2, which is a smaller roof area than most modern houses have. Over a typical 12 months period we have to buy three to four truckloads of water, or less than 50kl/year! Those 50kl plus the rainwater collected are sufficient to supply the household with all the water needed, plus the grey water was sufficient to supply our original gardens (which are much larger than any suburban garden). And Hobart is the driest capital city in Australia! If a standard suburban house would use the roof to collect rainwater, if this rainwater was used in the house, if a composting toilet was used and the grey water was kept as clean as possible and then properly treated and used in the garden, the average Australian home would need extra water totaling less than 10% of the town water allocation we had in Townsville and every garden could be green! The current "water crisis" in Australia really is no crisis at all. However, one question remains: how will extended use of grey water in the garden influence the soil quality? We used our grey water for about two years and had no problems. But the quality of the grey water depends on a lot of things: are grey water friendly detergents used? In which quantities? How is the grey water treated? There surely must be a way to end up with treated water from shower, laundry and kitchen, that can be used in the garden without any negative effects for extended periods of time! Room for experiments!

The rota-loo composting toilet

left: the toilet doesn't look much different from any other, but there is no cistern and no push-to-flush button  right: the waste container that holds the six rotating bins. Ventilation pipe in front

For us there was no question at all about the type of toilet system we wanted to install. It had to be a composting toilet! We definitely did not want to use our valuable water to flush the toilet, and we did want to keep the toilet waste separate from the grey water. We decided to install a rota-loo composting toilet in our house. We use a separating pedestal. The urine is separated from the solids and goes into the grey water system, where it can be treated and end up in the watering system for the plants without any problem. The temperatures in Tasmania are too cold to allow the heap in the composting toilet to dry out enough in winter if the urine is not separated. The rota-loo uses six bins which are rotated every time one bin is filled. Average time to fill a bin is about four weeks with three people using the toilet. Six bins by four weeks averages about half a year. It will take half a year before a bin needs to be emptied and that bin has been out of use for about twenty weeks at time of emptying. This means that the contents of the bin are already well and truly on their way to turning into compost when the bin needs to be handled and emptied. The level inside a full bin will drop down to a quarter in the twenty weeks the bin stays in the system before being emptied! We have no smell in our toilet. A small electric fan pushes the air in the system through the exhaust pipe which ends more than a metre above roof level. The only issue with the rota-loo (and all compost toilets) are insects. Under certain conditions flies can breed in the toilet. If the toilet room is to bright during daylight hours these flies (mostly small fruitflies) can be attracted to the light and into the room. We avoid excessive light in the toilet and seem to have the flies under control. After two year of "rota-looing" we can only say, we would buy the system again, and we definitely do not regret that we don't have a flushing toilet!