Plan Your Own Water Supply
Hi. I’ve listed a few tips on how to plan for your own urban water supply based on the system that is being planned for our house. Health and sewer regulations vary from area to area. Please contact your local authorities to understand the requirements that will apply to you.
Why?
Because you can.
Independence from the water grid in the event of a systemic failure.
Choose your own level of water quality and additives.
Preserve the network dams and groundwater sources.
Reduce the power required for desalination.
Collecting rainwater significantly reduces the surge in the stormwater system that damages local creeks when arriving by pipes and addresses the local water balance by helping to infiltrate water closest to where it has fallen.
Source
The obvious source is rainwater from your roof and grey water from the shower/bath and washing machine. Using black water from sinks and toilets is much trickier and not discussed here.
How?
Do a household water balance.
Calculate the weekly, monthly and annual water needs. This is likely to include showers/baths, washing machine and dishwater, drinking and cooking and hand basin and sink use. A really important additional calculation is garden irrigation water, particularly if you are going to grow food.
Remember that monthly water needs are likely to vary considerably if you irrigate a large garden but water requirements may not differ significantly season by season inside the house.
Our water budget for a household of 2 adults and 4 children looks something like the list below. I have tried to be accurate and over rather than under estimate;
Daily use inside the house
6 x showers for 6 mins @ 10L/min = 360L
30 toilet flushes @ 6L flush = 180L
washing machine 2 loads/day @90L = 180L
Dishwasher 1load/day @ 50L = 50L
Drinking, cooking and hand washing = 100L
Total daily use = 870L (about 320,000L/yr)
Grey water portion = 700L (about 255000L/yr)
Garden use per year
40 fruit trees @10L/day/200 days = 80000L
100m2 vegetable garden on dripline @ 8L/m2/day/300days (2L/hr/0.3m spacing/12.25 drippers/m2) = 242550L
Garden hose 25L/min for 5min/day/200 days = 25000
Poultry 20L/day = 7200L
Total garden use per day over a year = 1325L (200 days), 800L (100 days), 20L (60 days)
About 350000L per year
So we can see in our household water use is dominated by garden irrigation needs, because we will grow a significant amount of our own food (and save countless food miles, and get fresh organic varieties that you will never see in the shop because they often don’t store or travel well).
Grey water will, on average, as calculated, supply about half of our daily irrigation needs (providing we are all at home using water as calculated - which of course will often not happen!). An interesting consequence of this system is the lack of need to save water by having shorter showers. Watch how happy that makes the teenagers!
Information you will need
The size of the roof area that you can safely collect water from. Beware of roadside pollutants, chimney soot deposits and industrial contaminants that may affect the quality of water from your roof catchment. If in doubt get the water tested at a government accredited laboratory.
The frequency, quantity and variability of rainfall in your specific area.
Your household water budget.
The number of days of water storage you desire, based on your water needs.
Equipment required.
Separate piping from the shower/bath and washing machine
Grey water filtration unit
Grey water storage tank
Grey water overflow diversion to the sewer
Gutters and down pipes
First flush divertors
Rainwater tanks and pumps (25000L+5000L small tank pumps to large tank)
Water switch to and from mains supply
Plumbed connections between the grey water, rainwater tanks and the mains.
Reticulation controller (separate stations for trees and gardens)
Drippers, dripline and connections
What you will need to achieve
A system that will efficiently filter your grey water for use in a dripline irrigation system.
A pump and connection to deliver rainwater to the house.
A water switch that delivers mains water when rainwater is not available.
A greywater storage unit that is automatically topped up by, or switched over to, rainwater (or mains) to deliver the volume of water required for the days irrgation.
A sewer overflow and diversion valve so that excess greywater is safely diverted to the sewer when not required, or if the irrigation system fails.
Sufficient flows of blackwater in the sewer system to prevent build ups and blockages.
Garden friendly, very low toxicity body and clothes washing products for shower/bath and washing machine (there are many, and an ever growing range of products, that fit this description).
Cost
The cost will depend on factors such as:
How much you can do yourself
The price you can obtain the necessary materials
The cost of the plumber (be prepared - get an upfront quote)
Government rebates you are able to access
The degree of self sufficiency you desire
Some of the major expenses are:
25000L tank $3500
5000L tank $1000 to $2500 (slimline)
Water Switch $1000
Pump $1000
If you do just about all of the work yourself, and have the plumber come and connect things and sign off on the installation, I estimate the system as outlined to cost around $10000.
Final words
Whether the decision to increase the level of self sufficiency of your water supply is environmental, ethical, health related or economical, or a mix of them, I reckon it makes sense.
I think that if we used our total roof catchment of about 200m2 including shed, pergola, carport, etc. and had storage for 30000L (25000L at the front + 5000L at the back where space is limited) of rainwater we would reduce our reliance on the mains supply by around two thirds. In Perth we usually have a long dry spell over summer and autumn, although we do get considerable rainstorms on the odd occasion during this period. To capitalise on these events we need moderate rainwater storage and a large catchment area (A 20mm rainfall event would return around 4000L or less than 3 days of storage!). If the rainfall was more regular and less variable we could have a smaller system for the same result.
If you have a catchment area of about 100m2 and a rainfall of 1000mm per year (i wish) you could theoretically collect 100m3 or 100000L, assuming no loses and unlimited storage. Based on our water balance, rainfall, catchment area and 30,000L storage we could run exclusively on rainwater for about 7 months of the year. Another 25,000L tank (and $3500) would only extend this by about 17 days. When running off the mains our grey water system would still supply about half of our garden irrigation needs. My experience is that things always find a way of not quite going to plan and hence I think a figure of about a 66% reduction in mains water use is likely in this scenario.
It all adds up. Our solar panels make most of our power needs, our chooks give us eggs and manure for fertiliser, and we can compost and reuse of all our own organic wastes on site. Compost can be used to good effect producing a significant portion of our fresh food. A large measure of self sufficiency in water is a natural extension of this system, and another relatively easy step towards genuine urban residential sustainability.
What do you think?
Great plan, I already have my own water catchment and energy generating plant for all my needs.
Ke Shun said this on June 23, 2009 at 10:18 pm
Thanks. That’s great. I’d love to hear about it.
Paul Lock said this on June 23, 2009 at 10:48 pm
This is great Paul. My household has been quite savvy in finding great ways to save and re-use water, but we are not technologically ‘advanced’, which tends to inhibit us from trying to go the whole hog and invest in constructing new systems. This gives me a little more confidence ot keep finding out more.
I have a firned who installed a grey and black water re-use system when they built their house 8 years ago, and it’s fantastic. They have a beautiful garden that is watered completely form an underground irrigation sytem that flows from some filtration sinks underground. At the time it cost them $10 000. When the state govt built the desalination plant I wondered how many new houses could have been provided with one of those new systems for the cost of building and operating the plant.
Helena said this on June 24, 2009 at 11:44 am
Hi Paul, We live on a few acres so we have the advantage of extra room. Our 100,000L rain tank provides enough water for internal house use (everything) for 2 adults being reasonably conservative, even in years when we have had little rain, for the entire year. From the house roof and patio approx 200sq m we could easily fill more capacity as we nearly always have run off once the tank is full. From our experience our collection of water only happens for 6 months a year, very rarely do we get any significant contributions through the 6 summer months.
We did not put any grey water divertions in when we built 16 years ago as it was not legal at that time, we do have septics and leach drains which filter through the sand pad we had to install to bring the house level to the required height so that contributes to keeping the ground around the house watered.
We also live over half a km from the road and the available elctricity grid supply so decided not to connect and put a total of 10 x 650watts solar panels and a wind turbine 1kva on a 20m pole with a backup gen-set. As we do not have neighbours closeby this is not a problem. We are conservative with our electricity usage but still do not go without, with only one or two modifications when we built we have been able to manage quite well for 16 years self sufficiently.
In suburbia a number of things are still possible from our system that would not impact on neighbours, especially the solar panels and they have reduced in price quite considerably since we installed them. ALso either the reverse meter to feed electricity back into the grid or an invertor so that you can use immediately. Also having the space we have cells to store and use on demand the electricity we generate.
I am not sure what the cost would be now although 16 years ago all up it cost us $35,000 for solar panels, turbine, and generator etc., with varying government grants for different aspects and the cost to connect to the grid, due to distance was almost the same.
I agree with Helena if only the government had the forsight to invest in more renewable energy type projects especially in new housing subdivisions.
Ke Shun said this on June 24, 2009 at 1:17 pm
Paul this is very good info on setting up a water supply based to save what we all need water. better costing would be good to know approximately how much the set up would cost but i can see the long term savings to me and the environment would out weigh the set up cost.
Peter said this on June 24, 2009 at 1:44 pm
Thanks for all the comments. They are really helpful. I have now reworked the figures, resized the system and added some costs.
Paul Lock said this on June 24, 2009 at 2:49 pm
Hippy
Tom said this on June 26, 2009 at 9:44 am
well done. be interested to know which type of greywater filtration system you decided on. i assume you are planning on plumbing in rainwater for drinking purposes. i rememember reading a story on a sydney family who wedged between two highways were virutally water self sufficient and found that the bacteria and sediment that developed in their tank actually locked up heavy metals etc.
nic said this on June 26, 2009 at 10:47 am
Who is this and what are you talking about, Its too wordy and there looks like theres maths involved, can you give me the quick gist of it without all the pontificating or make some kind of music video that explains it more clearly, perhaps thru Contemporary dance.
Glen said this on June 29, 2009 at 9:37 am
Comedians. Who taught you monkeys to use a keyboard. When i get to work I’ll help you two back into the trees. Thanks for checking out my blog
Paul Lock said this on June 29, 2009 at 9:51 am
Seems pretty clear to me, but I think Glen’s idea about making a music video would be fun! Or maybe publish a book on “How to plan your own water supply for dummies”. Might be good to plan the garden so that water use is most efficient - like arrangement of plants, water-efficient species, etc.
Bonita said this on June 29, 2009 at 2:15 pm
After reading you article i realize that we have an advantage in Mexico because, most Mexican house has a tinaco. A tinaco is a large (~450 gallon) water tank is on the roof of every Mexican home; every evening the local municipal water is pumped to the tinacos of houses. The tinaco provides the household water supply for an entire day, and its contents can make the difference between loving and hating life in Mexico (particularly to a gringo) But if we manage to conect half of the houses to rainwater will be great.
Ana said this on June 30, 2009 at 11:59 am
good work .
i wonder if you could make up some sort of brochure that you
could gie to your council who would pass it on to home builders.
some way to get that information to the new home builders
before they submit thier plans .
as most people i know , water and energy use seems to be an
afterthought .
brett m a s h said this on June 30, 2009 at 10:05 pm
Thank you so much for your practical blog, it clarified a lot of things for me and helped me understand that I can make a difference even in suburbia. I think you demystified the whole set up requirements really well. I am going to print off your blog so I can discuss with my husband how we can set up a similar system for our home. We don’t have children but we have 4 dogs (and more sometimes as we rescue and foster them) and its amazing how much water they need! Kindest regards Julia
Ju said this on July 14, 2009 at 3:04 pm
It makes me very happy to know that people are finding this blog site useful. I would like to know how people find it.
Regarding the spread of information for homebuilders. The most powerful messages that inspire action tend to come through word of mouth and communication with friends and family. Never underestimate the positive effect you have when speaking to others about positive change. You never know how big the snowball will get, or where it will roll, when someone takes the information from you and spreads it themselves.
Paul Lock said this on July 15, 2009 at 12:03 pm