An outline of my plans - Rainwater

In coming days, I will be posting images and detailing each part of the build and the challenges I have faced in the lead up to both the renovation and the off-grid project.

But first things first, let's start with my plans for rainwater!  Let me say exact calculations are difficult because the variability of:
- rainfall across the country
- household habits (how long is your shower, how often do you cook etc.)
- efficiency of appliances
- gardening habits (how big and thirsty is you garden and soil)
- intended use of rainwater

Like two million Australians I will be drinking rainwater rather than mains water.  In other words I will be disconnecting from Sydney water. This will save me a quarterly connection fee of $25 ($100 per annum) plus the usage charges.  In my last 12 months in the house, I used around 87,000 litres of water and on top of the connection fee, I paid around $190. In addition to water charges, I also paid Sydney Water an annual service charge of $570 for sewerage and $70 a year for stormwater drainage. So, in one year as a single person I pay close to $1,000 for water and other water-related services.  It seems crazy that we city dwellers accept this as a cost we have to bear.

Question #1: Can I legally disconnect from mains water.
You are completely in your rights to disconnect!  There is no law in NSW or other states preventing us from drinking rainwater.  Thanks to Michael Mobbs for pioneering this in the city.

Question #2: Is rainwater safe?
This is the biggest concern of anyone who has only ever been connected to mains water.  The answer is a resounding yes, but you need to make sure that you have a properly installed tank. Management of the tank is simple if it is well plumbed!  By this I mean, the first dirty water has to be diverted to the garden.  Allow about two litres to be diverted for every 20 square metres. This can be done by installing a water diverter with a slow release plug in it. While it rains the dirty water slowly drips away and when enough rain has fallen, the roof and the gutters are clean and the water is now clean enough to be diverted to the rain tank.

I am going to use the first flush diverter from Rain Harvesting. This is the system Michael Mobbs has been using for 19 years to get water that he has found is cleaner than town water.  The first flush diverter is self-cleaning with the wind blowing out any debris. This also means that sludge doesn't accumulate in the tank which means I don't have to clean the tank. It costs around $20. 

A clean gutter is also critical. So what I am going to install is a self-cleaning gutter system from Smartflo.  The cost of the Smartflo is approximately twice as much as typical open gutter but lasts twice as long and gives much higher quality water.  You also don't have to maintain them, so there is no climbing on roofs.

 An example of a smartflo gutter

An example of a smartflo gutter

Michael has tested his water and you can see the results on his Rainwater Fact Sheet over at his Sustainable House website.  But if you're not still convinced, you can take a one litre sample of your rainwater in a sterile bottle to a pathology centre and get your rainwater tested for $50.

I will be testing my rainwater and publishing the results to prove that my water is safe. So stay tuned.

You can also put a water filter in. They filter out biological and metal pollutants. You will have to clean those every 3-6 months. I haven't decided if I will put one in yet.

I have also had my local council tell me when I was lodging my plans that they are concerned because there are more heavy metals in city water versus rural water. Once again I would suggest reading Michael's Rainwater Fact Sheet as he found his water was well within the National Health and Medical Research Council Drinking Water Guidelines.

The other question people ask is Fluoride. If you are worried about your kids, the dentist can put fluoride on their teeth when they go for their regular check-ups. If you are concerned talk to your dentist about this.

Question #3: How much rainwater can you capture and how much do you need for your household?
To answer this depends on what you want to use the rainwater for.  I am going the full monty; I will be using the rainwater for drinking, washing clothes, taking showers, watering the garden and washing dishes.  I could use the rainwater for flushing the toilet, but instead I will be installing a greywater system. Having a greywater system will reduce your usage of rainwater by about 50 per cent which will mean less rainwater to store. It will take a big chunk out of the 48,000 litres of water per year I'm estimated to use once all my efficient taps and appliances are in. 

There are two parts to my roof. The front part of the house - where the roof is quite small (see below). I will be diverting the rain from those downpipes into my water tanks via a pipe under the house. You can see the gutters are full of branches and I can't wait to have those self-cleaning gutters.

great image of front of house_LR.jpg

Below is my current back roof, which is more expansive than this photo captures as it goes right up to the chimney. Because I am going up a level I will have a flat roof that is the just below the peak of my neighbour's house on the right.  This won't significantly impact on the amount of litres I capture.

Calculating how much rainfall you can capture
To calculate how much your roof can harvest, multiply the area of your roof by the average rainfall in your area from the Bureau of Meteorology. For example, if you have a 100sqm of roof and 1,000 mm of rainfall a year, that is 100 x 1000 which equals 100,000 litres of rainfall a year most of which can be held by a 10,000 litre tank. 

If I were to capture every drop from my front and back roof, I could harvest approximately 97,000 litres of water, my roof is around 80sqm and I have an average of 1213mm on rainfall a year (80 x 1213 = 97,040).  With 8,000 litres worth of rainwater tanks, I will capture most of it, with any excess it will go into my stormwater absorption pit. As rain and usage are unpredictable, these figures are to be taken as approximates. Generally it is best to have more storage than you estimate so that you can keep those big rainfall events in your tank.

Calculating how much rainfall you require to service all your household needs
If you have a water bill, look at the last 12 months of use.  If you use 100,000 of water, then you will need about 8,000 - 12,000 litres of storage, depending on where you live.  For example, in coastal QLD and NSW where it rains more you will need less storage than if you live in the drier western parts of those states or in Adelaide and Perth.

If you use a greywater system to flush the toilet, this will reduce your daily water use by about 50 per cent. If you want to further reduce your daily water use, install an efficient shower head. For a household that uses the shower for 20 minutes a day, replacing a 20 L/min shower head to an efficient 7.5 L/min model results in a savings of 250 litres per day or about 91,000 litres a year!!

Question #4: Costs

You can install above or below ground rainwater tanks. Above ground are the simplest and cheapest to install.

I have a little yard less than 30 square metres, but I still could have fit 8,000 above ground, and as you can get modified rainwater tanks to suit your backyard design, they don't have to dominate. However, I have put 5,000 litres underground. If you want to save money and time, then don't put tanks underground. However if space is of paramount priority, then you need to know that the tanks are more expensive, are trickier to install, you will most likely need council approval to dig a hole that deep and you will have the extra costs of digging, securing the tank and building over it.

Before you go down the underground rainwater tank, consider the impact of installing a grey-water system as mentioned above, to flush the toilet and water the garden. This will reduce the amount of coverage you will need from your water tanks.

The other complication I found from having an underground tank is that council tend to interfere and create confusion. Don't let this be the thing that puts you off as it is easily overcome. I think there is an argument for the laws being made a hell of a lot clearer to reduce this confusion. If you plumb your above ground rainwater tank into your house, council don't need to be involved.  If you have a tank underground they are aware as you will most likely have to get approval to dig the hole.  After much discussion with my council we have agreed that I will erect signs on my property saying that rainwater is in use on the property.  I'm cool with that. At the end of the day with two million people safely drinking rainwater, it's ludicrous that there is this confusion. 

With the above ground tanks, I am getting two 1,500 litre tanks from Tankworks and they are making them so they are .95m tall and .65m wide 2.6m in length each. I am incorporating them into my deck and I will use them as shelving space or where people can sit. So the tanks don't have to be so obvious and can be a part of your furniture.

So the payback for above ground is a lot quicker, but like with every decision you make, it depends on what is important to you. People spend a fortune on kitchens, you may decide you want to spend more money burying a tank. I just want to alert you to the different pricing, approval and time implications it may have.

Question #5: What do I do if I run out of water?
I've done my water calculations and I am pretty confident I will not run out. But even if I do, I will get the tank filled up and that will cost me $250 for 7,000, still miles cheaper than staying connected to mains water.

Phew! I'm think you are ok to go and drink rainwater now!  :)