Over Christmas, when we had three dry months, our tanks dropped to nearly empty. They also started to stink, clearly the results of anaerobic decomposition of the plant material washed off our roof. Smelly water feeding into the washing machine, not good!
Our setup has first flush diverters, designed to capture the first lot of dirty water that flows into the gutter. They’re not magic, however, and gunk still gets in to the tanks, and builds up over time.
In the country, where households have to rely exclusively on their water tanks, it’s routine to get them cleaned out every while. I haven’t heard of it being done in the city, however. This might be because most of the tanks were put in at the same time as us, or later, and the problems are only now starting to emerge.
When we were out at a country show, we collected a business card from Leigh’s water tank cleaning, who we talked into dropping by our place when he happened to be heading into the city. We also talked to the Water Tank Cleaning Company who operate throughout Sydney (their website was down at the time of posting).
Leigh was very friendly, the the process is surprisingly simple. It’s basically a hand-manoeuvred version of a pool cleaner, which is steered around the base of the tank where the gunk has accumulated.
It’s somewhat horrifying to see how much dark brown water gushes forth. No wonder our water filters kept getting clogged up, trying to deal with all that!
It’s a quick process, and within half an hour, our two main tanks were done. That should keep them going for a few years…
The photo above underscores what street trees often have to suffer through.
With the trunk surrounded by concrete on all sides, the results are lifted pavements for pedestrians, and too little water for the tree. Amazingly, some people call for the offending trees to be cut down, but there’s a better solution.
Why not give the trees more space?
Marrickville Council is one council pursuing this policy. When a pavement comes up for renewal as part of the regular maintenance (planned five years ahead), a bigger opening is left for trees.
This gives the trees more space, and allows more rain to absorb into the ground, rather than into the stormwater system. I imagine it also saves a small (but measurable) amount of concrete.
Biodiversity is also increased when low plants, such as lomandras and dianellas, are planted around the base of the trees. With an even larger space, it becomes possible to establish a true verge garden.
Marrickville Council also goes beyond this. At the time of writing, the Sustainable Streets program enables residents to cut spaces out of their concrete verge for a small fee. If the majority of a street requests street gardens then the council will cut out the concrete, provide some extra soil, and even throw in some plants for free.
As a final note, this pavement work next to Petersham Park is another small but elegant example of the principle at work. Instead of re-laying the whole pavement with concrete, gravel was laid down for half the width. When I talked to the Council about this, they highlighted the benefits of less run-off, as well as providing more rain for the avenue of trees.
Councils have a big role to play in the sustainability of our local environment. If we can keep changing default policies to encompass environmental thinking, we’re well on our way to saving the planet!
A green roof is where a garden is installed to cover a roof, typically to a depth of 150mm on top of a strong waterproofing layer. It’s a great way of getting extra greenery into a property, and the roof also asborbs water run-off.
About a month ago I stumbled across the book Small Green Roofs, on Amazon. It’s a wonderful book that has 40 different inspiring case studies, all covering small, non-commercial green roofs (full book review to come).
Feeling inspired (and running short of projects around the house), I decided to construct a green roof at the end of the chicken run.
At 1.2m x 1.6m (1.9m2), this may be Sydney’s smallest green roof.
When we created the chicken run, I installed several left-over sheets of Colorbond at the end of the chicken run, to give cover for the chicken feeder (and the chickens!). This is now replaced by the green roof.
The starting point was to install a sheet of 25mm exterior-grade structural ply. This is very strong (and heavy), and it provides the base for the green roof.
The next challenge is to deal with the extra weight of the green roof. For a soil depth of 150mm, a green roof weighs 250kg per sq. m. That’s a lot!
Thankfully the chicken run was constructed strongly in the first place. To provide extra support, I installed a new vertical post (front left corner of the new green roof in the picture above). This was concreted into the ground. Extra rafters were installed, along with bracing back to existing posts.
Other than the structural ply, everything else used wood and materials salvaged locally, or left over from the house renovation.
The sides of the green roof were constructed out of left-over roof beams, 200mm high. Because the sides of the wood were very uneven (from sitting in the weather for 10+ years), I put in an extra layer of ply to assist with waterproofing.
There’s a 20mm gap along the bottom edge of the green roof, to allow water to drain away.
I had some left-over “pond liner” paint, so I used three coats of that to seal the base and sides of the green roof. On top of that I installed a layer of 20mm Atlantis flo-cell (left over from the reworked raised garden beds). A layer of geotextile then keeps the soil out of the drainage system.
As a stroke of luck, just as I was ready to fill the garden bed, a friend rang to ask whether I needed any soil, as he was clearing out his back garden. A ute load’s worth of soil later (courtesy of GoGet), this is the final green roof.
Green roofs would typically be planted with sedum (a low growing succulent), to cope with the extreme conditions and low water levels. In this shaded position, however, that isn’t an option.
Instead, I’ve put in some water crystals, and have planted out the garden with a mix of:
- native ground covers (native violet, white root and northern cranesbill)
Already it looks great from the back verandah, and I’ll blog new pictures in six months after (hopefully) the plants have all grown up.
A key element of our watering system, fed by our rainwater tanks, are the “water spikes” used in the beds themselves. I was sure we’d written about these when we first put them in, 3+ years ago, but I can’t find a post for them. So here it goes…
These spikes are traditionally used with grey water systems, as they have two pairs of drainage holes 10+ cms down (the regulation depth for grey water usage). According to our plumber, one spike feeds about a circle about 1m in diameter. To be on the safe side, we’ve got three for each raised bed. (We’ve also strategically used them throughout our new native garden at the back.)
The big advantage of this watering approach is that practically no water is lost to evaporation, as it all goes sub-surface. It also encourages plant roots to seek downwards, strengthening them again dry and hot days. It’s robust against blockages, as any sediment simply falls to the bottom of the water spike.
We had a whole bag of spikes supplied as part of our water tanks, already made up. But you can also make them yourselves, as follows:
- orange water spike (our plumber called it a ‘carrot’, for obvious reasons)
- 25mm end cap (standard item for 25mm polypipe watering systems)
- 3.5mm hole drilled in the top of the cap
- standard 4mm elbow inserted (heat the cap in hot water first, and use pliers)
This creates a ‘watering unit’, when then connects to standard 4mm polypipe (used for drip feeds, etc).
I’ve seen the ‘carrots’ available per piece in Bunnings, along with the other required bits. You can also get them in bulk at Reece.
Combined with a timer system and a network of 19mm polypipe, this is a great set-and-forget watering system for all our plants. We love it, and would recommend it to others.
One of the first things we did when we purchased the house was to put in a water tank, to allow us to grow our own food despite the water restrictions in place at the time.
The renovation gave us an opportunity to expand our water capacity. The easy step was putting in a second 3,100L water tank in beside the first, at the side of the house. Since this one could just be connected to the existing tank, it’s pretty cheap (no pumps, plumbing, etc).
The last water tank was a slimline tank, put in to address our overflowing gutters. With the extension finished, we had 150 square metres of roof feeding the back gutter, and with a single downpipe, it would get overwhelmed in heavy rain.
The slimline tank on the other side of the house allowed us to put in another downpipe. By connecting the new tank to the existing tanks, the water level equalises between them, adding 1,500L to the total capacity.
So that’s 9,700L of water capacity, split across three tanks in two different locations, with just one pump. Not too bad!
This diagram shows how it all fits together (click to see a larger version).
Marrickville Council has organised another Water Sustainability Urban Design (WSUD) tour in the local area, and we’re one of the stops.
The purpose of these tours is to show local residents some of the many ways of saving water. In our case, it’s our water tank, irrigation system, and permaculture garden sufficient to meet our vegetable needs.
See you on the day!
Our last quarterly water bill was $248. This is too cheap. With water rates at this level, there is simply no way of economically justifying any of our water efficiency measures.
We’re not very efficient users of water yet. Having moved into a 100-year-old house, there’s plenty of progressive improvements to be made:
- installation of low-flow shower head (done)
- fixing dripping taps (done)
- water efficient washing machine (done)
- use of tank water for toilets (1/2 done)
- installation of dual-flush toilets (when we renovate the bathroom)
- installation of low-flow taps (now or as part of kitchen and bathroom renovation?)
- water efficient dishwasher (when kitchen is renovated)
At present, our water usage is 494L/day,which is the same as the target rate for a 4-person household. It should be down at about 300L/day. So plenty of water savings to be made!
But let’s look at the economics of this:
If we got our water down to 300L/day, that would be a saving of 70kL per year. At a rate of $1.87 per kL, that would be the princely sum of $132.
That’s right. If we drop our water usage by 40% (!), we could save $132 per year.
On that basis, the water tank would take 50+ years to be paid back. Even a low-flow shower head ($80) would take several years to recoup the cost.
We’ll make the changes because we care about the environment, and it also makes us feel good. But spending thousands to save at hundreds doesn’t make a lot of sense in dollar terms.
Our comfortable middle-class life allows us to spend money on these things, but if money was tight, this wouldn’t even get on the list. If we’re going to get serious about water efficiency, the laughably cheap rate of water needs to be increased, and dramatically so.
I recognise that thisn’t an easy change, and that measures would need to be put in place to ensure that the poorer segment of society aren’t hit hard. But surely we can’t keep going on like this?