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Advice on best rainwater harvesting system for suburban house

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    I am looking for advice on the best setup for rainwater with mains backup to our new house.

    I have done things the wrong way around and now the house is complete I have only just started researching rainwater harvesting systems! I am very confused and just want a simple system that isn’t too expensive but one that will obviously harvest as much rainwater as possible on a small block with limited space.

    The block is 521m2 block. House is 182.94m2 courtyard style. We had a rainwater by-pass system built into the house so that all wet areas are plumbed to rainwater and mains. Toilets and gardens to mains only. This is the setup the plumber recommended and we just went with it and didn’t question it ( I was very stressed at the time with health issues and the whole house-building experience)! Sometime in the future we are hoping to set up a greywater recycling system so that the water used in the bathrooms etc. can be used to flush the toilets and water the garden.

    Would it be better to go for one huge underground tank or lots of small above ground poly tanks positioned around the house where we can fit them, all connected together at the bottom feeding into one main input and overflow tank? Hope that makes sense!

    Just thought I should add that to complicate things the house is a split level design with the garage set down 1029mm from rest of house so we would have to put tanks on that side of the house on a stand of some sort to bring the top of those tanks level with the others (I believe this is what you have to do if you want to connect all tanks to the main input one).

    Any advice would be very welcome 🙂

    Many thanks



    g’day christina,

    for me it would be a tank of sufficient size eg.,. around 25k/litres is a good family sized tank for areas that get around 700mm to 1200mm of annual rainfall.

    now as for using the water in your home (not that i agree with the following) talk to your local council about their regulations, or be ned kelly about just do it and tell no one.

    most councils allow it to be used in the toilet, laundry and bathroom, which means with the way they do modern plumbing you would need to plan this real early in the project.

    like grid connected solar, water system mains connected tanks can be an expensive operation.

    the least you can do is fit up a tap where you can say fill a water urn and sue that water maybe for drinking, cooking or whatever. use a hose to fill the wash machine and rinse tub, works best with a twin tub washer.

    but in all cases one big tank better than smaller ones.

    people in rural and urban rural allowed to live with tank water alone but suburban people not given the same right.



    It’s my impression that councils are lightening up a little on using tank water in the house. That was the impression we got when we talked to the Caboolture council when planning our house (4 or so years ago now!)

    I have heard advantages to having more than one tank in that if something happens to one (develops a leak, gets contaminated etc), you have backup. That only works if they aren’t connected underground though, and involves annoying hassles like having to pump from one tank to another.

    We have two 26,000L tanks. One collects water off our shed roof, and is used for the kitchen, bathrooms etc, and the other collects off the house roof, and is connected to the toilet, washing machine and outdoors. Not the order I would have arranged them, but that’s just the way it happened. Usually by the end of winter we’re transferring water from the one that serves the toilet and washing machine into the other tank.

    When we run out of water (really need to stop showering like it’s summer and the tanks are overflowing before the water gets so low! The amount we have really should last us!), we transfer the last of the water from our toilet/washing machine tank to the house tank, and fill up the toilet/washing machine one from mains. We have a little top up thingy that the builder installed for this.

    We used to have a water switch on the house tank, that automatically switched from tank to mains when the tank was empty or the power went out. A good idea in theory, but I wasn’t impressed by the fact that the water switch used mains water to prime the pump, so that we were fine if the power went off, but if they turned mains off for any reason, then the pump didn’t work. Not cheap either, the pump and water switch combo was about $1k.


    Thanks for the advise. Much appreciated. The decision has been made for us now. I looked up underground concrete tanks and it appears you need council approval for them and we can’t wait that long as we have to be out of our rental property by 26th October. I’m going to see Team Poly tomorrow to get prices on slimline poly tanks and a pump. I think an underground tank would have been a bit beyond our budget anyway as it would be extra for excavation costs etc.

    Thanks again


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