# Forum Home Renovation Water Saving Garden Ideas  rain rain.... how much really?.....

## sundancewfs

I just did a interesting experiment.
I put a 60 litre bucket under the overflow of my 2100 litre rainwater tank.
I thought I would time how long it took to fill, under the light/moderate rain we are having now.
It took 6 minutes. 10 litres a minute. This is just off one down pipe.
By my calculations it would take only 40 hours of rain to fill a 24,000 litre tank at the same rate of rainfall.
Thats less than 2 days of rain to fill a quite substantial tank.
Interesting......

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## Dan574

It is interesting, on average 1mm rain x 1m2 room area = 1 litre of rainwater, according to the expects.  There is a product on the market that fits into the lowest point of the stomwater drain, it blocks the pipe and then uses the pipes to store the rain water before pumping it into your water tanks so that you dont have to have the tank connected to a downpipe, it uses all the pipes. 
Now imagine if the government got serious about new constructions both residential and commercial and made it mandatory to put in large tanks instead of a 5000l token effort.

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## president_ltd

i'm in East Malvern, have about  11300L of tanks (1x3000L round, 2x3300L round, 1 x 1700L bladder under house).
we pick up ~98% of our roof surface area and have a setup whereby the larger round tanks 'overflow' into the under-house bladder which in turn overflows into the storm water. 
pump can draw water from all of them.  we use some non-return valves on the connections to the pump, use a Davey Rainbank & have the toilets & various bits & pieces all plumbed up to the tanks. 
i added a few thousand L to the pool a few days ago, so that 11300L was at least down to 8000L if not less. 
this setup is almost permamently 'full'.  doesn't matter how much water we use, have a downpour like what happened overnight/this morning, its literally a fire house of water coming out the final overflow-to-stormwater. 
my estimate is its easily 1L every 3 seconds, or 20L/minute.  could well be double that in a heavy downpour.

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## SilentButDeadly

....at least you Melbourne buggers get rain! 
The 18mm of rain we got here the other week was the biggest district wide fall in two years.  And our biggest since a January storm.... 
Still have plenty of drinking water from our tanks.....takes a while to go through 23,000 litres.

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## Metung

Wouldn't fancy lugging that bucket around when it was full of water :Eek:

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## Ronaldo451

Prior to moving to the smoke we lived on a property with 3 x 25,000 litre tanks fed from the house and shed - no town water.  
At one stage we got down to two empty tanks and only about 700mm deep in the last but a one-off weekend of solid rain (4 years into the drought) was enough to fill all the tanks to overflowing which lasted us another few years until we moved...... 
It is decepetive how much can be collected and it never ceased to amaze us after we moved to see the waste in all the stormwater rushing down the street gutters rather than being harvested.

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## Bloss

Just simple maths as as has been said - 1mm rain on 1m2 of roof gives you 1 litre of water running off and into any storage. So time to fill is volume of storage divided by total roof area captured x mm of rainfall in 'n'  minutes (or hours or days). Of course at some point in some storms the gutters/pipes might overflow and some runoff will not be caught in your tanks.  
This is a useful and interesting site on the subject:  http://dkacoolmob.org/rainwater.htm 
and it has a free excel tank water calculator you can download but uses data for Alice Springs!

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## MathewShearer

lol
yea interesting  :Smilie:

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## up_the_gully

I put in a 10,000L tank connected to the majority of our downpipes (at the bottom of a sloping block).  Within 2 - 3 weeks it was full and overflowing  :Smilie:   There's 5 downpipes and approx. 30m2 of roofspace which is collected.  It blew my mind how much you can collect, and this is not a very large house.

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## Neri

What's this rain stuff  that everyone talks about? I remember reading about it at school. I am limited to half an hour hose-watering and on alternate days! And Kevin Rudd and the Unions think Australia's carrying capacity could be easily increased to 35 million. I am getting seriously worried about ...water!

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## rrobor

I'm a lazy begger. .Begger this getting up at 6AM to water things, who needs that. I always believe in do it once and do it well. Well there's a Dutchman out just shy of Ballarat where the John Deere place is, who sells plastic crates that once contained bulbs. My front yard is full of these. 200mm wide 200mm deep X 2 X 600mm. Covered with weedmat and 200 mm of soil. Cost me $1 a crate and all my roof water fills these trenches and when full it just backs up and goes where it went before. 
I look out on my oasis in the desert and man, how good it that.

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## sundancewfs

rrobor,
Wonderfully simple, way of doing it. similar to the swale or dry creekbed idea, where you contain and direct the rainfall directly to where you want it.
We have two tanks, one 30000litres and one 2100litres. A couple of weekends ago we got 18000litres from saturday lunch to sunday evening. Now both tanks are overflowing.

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## chromis

> What's this rain stuff  that everyone talks about? I remember reading about it at school. I am limited to half an hour hose-watering and on alternate days! And Kevin Rudd and the Unions think Australia's carrying capacity could be easily increased to 35 million. I am getting seriously worried about ...water!

  All Unions think that do they? I'd like to see the article you read or where you got that info.

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## merecat

Back to a comment from a couple of years ago, in Qld there are mandated tanks (or other alternatives) minimum 5000L. This does not stop anyone using bigger tanks if they want to. However it's the yield of the tank that matters, how much you use before the next rainfall (hence plumbing into toilets and laundry), I reckon plumbing into more in-house uses like the hotwater system for example is a good option to get a better yield.  
In a city it is hard to get 20000L tanks on small blocks. I reckon 5000L is a good start,  but good on anyone who can do better  :Smilie:

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## Black Cat

Living in the country, I currently have a 10,000 litre tank that will be supplemented by two 20K tanks in the near future. The other day some genius left the tap on and drained the tank. Fortunately it rained three days later (and even more fortunately the plumber had finally connected the tank to the guttering). Off half the main roof and the roof of my new extension, I collected quarter of a tank (2500l) from 22mm of rain. I was stoked!! 
Storage capacity should equal the roof surface X annual rainfall. In my case 650mm av annual rain X 100m2 (roughly) would yield 60,000 litres, so I am still 10K short. 
Since there is only one of me, the 40K will go on the garden, and the 10K will do me for my own use. Now all I need to do it get those two other tanks hooked up in time for winter. I will be stoked if the third tank is overflowing before next summer as I will be putting a heck of a lot of fruit trees in this winter.

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## Moondog55

G'Day Black Cat
Tell me where do you run the overflow from the tanks/ Do you run them into the garden area or to a swale or dam?? 
One of the benefits of living on an acreage is the room you have to do stuff, on our block we are struggling to find room for a 1.5Kiloliter tank

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## Bloss

Moondog55 - Not cheap, and only useful if you have underfloor access and a bit of height but you could look at:  eco sac Flexible Water Tanks, flexible rain water bladders or underground tanks eg: WaterTanks DownUnder - Water Tanks for the Home or Toroid Water Tanks | Bushranger Watertanks (but of course you have to be doing a reno or adding a garage etc to get access) or the crate type systems like this that can go under lawns gardens etc: Ecowaterboxx - again you need to be able to get access. There are concrete options too. They all need pumps as well, but they allow use of the land while giving water storage. More expensive as they need excavation.

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## Black Cat

Sorry for the delay Moondog, missed your question. So far I don't have an overflow to worry about as I am only collecting off part of the roof. When I do have one, I hope to also have the two additional tanks. Once they are full then yes, it will be run down the high side of the property in ag pipe so it can water the lower portion should the need arise. On the lower side of the property there will be a ditch so that if we have too much rain, the excess can be drained into the rear ditch that runs along my back boundary. That lower portion will be orchard and the trees will be set on the high bunds between the swales. That is, however, still a work in progress, as is the rest of my life. This gets done between my increasingly urgent efforts to get out of the caravan and into the house before it gets too darn cold!!

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## autogenous

One of, if not the biggest waste of water is *your toilet*.  I believe it is *as much as 65% of potable water* in your house to carry the medium.  There has to be another way. 
Bio-cycle tanks are one.  If water becomes expensive it will be very economical just to recycle your toilet water to the tanks alone in an off the grid system totally disconnected from the grid. 
The problem is you'll still have to pay for deep sewerage to go past your house with bucket loads of money. 
If the authorities were serious about saving water this is what has to be looked at.

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## Black Cat

Too true. Grey-water recycling does help enormously in terms of dealing with the waste from toilets. Biocycles are great for those who can afford the regular service fees but as you say, if the Council is already providing a service you pay for it whether or not you use it. and this inequity does need to be dealt with.

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## Moondog55

> Moondog55 - Not cheap, and only useful if you have underfloor access and a bit of height but you could look at:  eco sac Flexible Water Tanks, flexible rain water bladders or underground tanks eg: WaterTanks DownUnder - Water Tanks for the Home or Toroid Water Tanks | Bushranger Watertanks (but of course you have to be doing a reno or adding a garage etc to get access) or the crate type systems like this that can go under lawns gardens etc: Ecowaterboxx - again you need to be able to get access. There are concrete options too. They all need pumps as well, but they allow use of the land while giving water storage. More expensive as they need excavation.

  Thanx Bloss, they look better than the Nylex on quit, we do have lots of under floor space.

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## Wombat2

We live in what is now the Sunshine Coast Regional Council and are on tank water. We have 52000 litres under the floor of the garage and usually have enough water. I just noted that the Council has decreed for new dwellings not on reticulated water must have 50,000 litres storage for 3 bedrooms and 60,000 for 4 bedrooms - we have 4 bedrooms. also in rural areas ( which we are) we must also have an allocation of at least 10,000 litres for fire fighting - this can be a pool or other storage such as a dam or added to the tank storage. Fortunately we have a 70,000 litre pool.  But I'm thinking of re-sale potential and may increase the house hold storage to new house requirements -ie add at least another 10,000. 
On the grey water side - we have a Super Treat sewer treatment plant and in spite of what the Council says where it is supposed to go I use it on the garden - including veggies.

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## DNL

I did the calculation off my 15m x 6m shed roof and worked out it would take a few days of moderate rain to fill 2 x 5k tanks.  
I hadn't plumbed the overflow into the stormwater, and went out after a few hours of rain and they were overflowing. The are still full. 
It is even more interesting to calculate the cost of tanks and installation versus the cost of buying your water. So far, it has cost me around $3k to buy, install and plumb. We get charged $50 per quarter for water use. Therefore that is 60 quarters or 15 years for me to recoup the cost of installation - take off say 5 years for price hikes and my tanks will only take around 10 years to pay for themselves. 
We are building a new house and wont be in this house in 10 years. Conclusion: all my money trying to be green is wasted, but I have contributed to the economy and had fun doing it all myself. 
I will do tanks again - I suppose I just like the concept of having water and not relying on the mains. Next time though, it will be more tanks and plumbed into the house. 
cheers

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## Black Cat

Bearing in mind a few variables (like the weather station is five k up the road and 100m higher than me), two inches of rain on a 70msquare collection area came very close to filling my 10K tank. If the whole roof was plumbed in, I would have had an overflow. Will start measuring my own local rainfall once I get the caravan out of the back yard and have a permanent spot for the rain gauge.

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## andy the pm

Moondog, 
Have you checked out auction houses in your area for rainwater tanks?
I was at one yesterday (in Sydney) and 2000L slimline factory seconds were going for $475, a 3000L slimline factory second was offered at $600. 
Andy

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## Moondog55

Hi Andy, yeah we have, the problem is the actual cost to get on-site after purchase ( we have a very Eco-friendly ( read small ) car, freight negates the cost saving unfortunately.

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## andy the pm

We're in the same boat really Moondog, the auction is in SW Sydney and we are in the Hunter Valley about 160k away lol even though I have a ute I don't fancy heading up the freeway with a giant sail strapped to the tray! I think the best way to do it is to buy enough stuff to make it worthwhile for a trucking company to shift it all at the same time.

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## RossForeman

Hi, I have enjoyed following this thread and thought I would contribute my experiences up here in Brisbane. We moved here from Sydney in 2007 at the height of the SE QLD water crisis and decided to do supplement the 1500L "decorative" tank above the pool filter area. 
1. Do your research: Before taking the plunge I did a bit of reading and can personally recommend the relevant chapter in "Sustainable House" by Michael Mobbs which details his experiences in turning an inner Sydney terrace house into a sustainable one. The other valuable source of information is the Bureau Of Meteorology site (BOM.gov.au) particularly for the detailed rainfall information which allows for planning of things such as yield and likely dry periods.
2. If not doing the job yourself, thoroughly check out the company that does the job. We got done over by a bunch of cowboys from NSW who stuffed up the install, didn't do the drainage properly and then promptly shut up shop. On top of which the existing tank was put in by a handyman who neglected to put any overflow on the tank resulting in water going under the house!!!
3. Peak rainfall events such as those big ole summer storms we get up here can mean overflowing gutters and tanks that unless properly plumbed in to the stormwater drains will put a lot of water in all the wrong places in a very short time.

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## Moondog55

really good post Thanx 
OK time to be reminded of the 6Ps motto 
Proper Planning Prevents Piss Poor Performance

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## Draffa

I have just finished doing some calculations for an in-ground tank under a future garage.  Even at slightly smaller than the garage footprint (as the garage is not a rectangle), it would still be 96kL if it was 2500 deep.  If I went to 3000 deep (no idea on the legality of that.  Maybe I'd have to line the bottom with milk crates or something to reduce the effective depth), it increases to 115kL.  My roof area (excluding future garage) is some 231m2, which means that where I live, that's 277kL of water that could theoretically be collected each year.  Since it's just me living here, I could get into the water supply business.  :Biggrin:  
Imagine if you were new-building.  Your entire slab area could be a water tanks if you had ~$15k-$20k handy.

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## Danny

I have dealt with a lot of people who have underground tanks installed and who are now having big problems with sediment build up and stagnation. The same goes for bladder tanks. For anyone considering these systems, make absolutely sure that the storage only receives clean water. The best way to do this is to use a first flush *AND* other additional filtering systems *PLUS* an above ground settling tank. The water can then be decanted to the under ground tank 2-3 days after it stops raining. 
There is a serious lack of expertise in this industry.

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## Draffa

> sediment build up

  I'll have to make the access hatch big enough to chuck a Kreepy Krawly in once a year.  :Biggrin:

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