Water tank. Divert water to mains.

[bricks]

As long as you put some sort of backflow on the line before the Y junction, Micks Idea ( Post #2 ) is probably the most reliable and user friendly.
It isnt quite right IMO because of the manual changeover but i suppose we do that on gas bottles so why not water supply.
I went to a house today that had what looked like 10,000 litres of tanks running down the side of his house with a filter and a pump connected, I asked him what he did for backflow protection he said " I disconnected the water meter ".
Simple and effective.
He claims not to have used mains water for the last two years he also runs some of his neibours gutters into his tanks. And his swimming pool runs from the tanks too for top ups!

[journeyman Mick]

Bricks,
if he's down your way then 10Kl isn't an aweful lot if the town water is disconnected. I've got a single 26Kl tank and it starts running a bit low after three months or so without rain. Our annual rainfall is measured in metres by the way.

Mick

[SilentButDeadly]

An issue with the Y thingy is remembering to switch it back.

The other useful things with that float valve thingy is that it tops it a little at a time with mains (rather than totally fills the tank) and provided that the tank over flow is below the level of the float valve you don't need backflow prevention because the tank water and mains water aren't within coo-eee of each other.

[bricks]

The problem of backflow exist's when the tank is full of rain water, and therefore is above the level of the float valve, backflow valves should be fitted regardless of the regulatory requirements IMO.

[RRick]

Hi Tourgy,

If you want to implement a Dual Water system legally in Australia then you have to ensure that any valve that you connect to the mains supply to supply water into your rainwater tank is WaterMark approved. In addition local shires have their own requirements. Many local authorities do not allow any Dual water systems that T into their mains supply. In these locations you have to use a top up system that utilizes the Air Gap method, whereby the water is filled from the top of the tank. (Some authorities require the Air Gap to be visible from outside the tank). You cannot in this instance use any float valve with a weighted float as suggested in one of previous posts (Many float valve are not WaterMark approved). You can legally uses any of these products. http://www.anadexlabs.com.au/shop/home.php?cat=243.
No backflow prevention devices are required if you used the Air Gap method.

By the way the $120.00 2" float valve referred to in one of the previous posts is not a ordinary float valve. It is in fact a Reservoir valve that is used in large tanks and can deliver 630 liters per minute at 300kPa. So that explains the price.

Regards,
Rick

[RRick]

Hi Tourgy,

If you want to implement a Dual Water system legally in Australia then you have to ensure that any valve that you connect to the mains supply to supply water into your rainwater tank is WaterMark approved. In addition local shires have their own requirements. Many local authorities do not allow any Dual water systems that T into their mains supply. In these locations you have to use a top up system that utilizes the Air Gap method, whereby the water is filled from the top of the tank. (Some authorities require the Air Gap to be visible from outside the tank). You cannot in this instance use any float valve with a weighted float as suggested in one of previous posts (Many float valve are not WaterMark approved). You can legally uses any of these products. http://www.anadexlabs.com.au/shop/home.php?cat=243.
No backflow prevention devices are required if you used the Air Gap method.

By the way the $120.00 2" float valve referred to in one of the previous posts is not a ordinary float valve. It is in fact a Reservoir valve that is used in large tanks and can deliver 630 liters per minute at 300kPa. So that explains the price.

Regards,
Rick

[Mcblurter]

In the process of getting a tank connected to my toilet and laundry. Hard to get hold of the plumber and wanted to know a bit about what to talk to him about.
Can someone tell me what i need to connect all this up.
Obvioulsy rainwater tank (looking at 2500lt)
A pump (what size would be adequate?)
Some sort of backflow valve
A sensor so when water low it goes over to mains.
Anything else, what sort of costs involved.
Just trying to get a rough idea of what it will cost to get all the bits!!
Cheers
McBlurter

PS: with all this water saving talk you'd think they would have a site that could explain how all this works. If you ring any plumbing supply place they all seem to want to sell you "Their" device, "all included" without explaining what it is and how it works!!!

[bricks]

In S.A. It costs around 600-800 to install the system not including the tank and stand.

Assuming its easy to get to the pipes feeding your taps.

[totoblue]

There's this device
http://www.irrigationwarehouse.com.au/prod2265.htm
"TMC - Town Mains Water Control"
It's not showing a price at the moment - must be free!

[Mcblurter]

There's this device
http://www.irrigationwarehouse.com.au/prod2265.htm
"TMC - Town Mains Water Control"
It's not showing a price at the moment - must be free!

Thanks for that. Would I actually need this or is it overkill?
I would assume all I need is some connection from the tank to the mains so water can get from tank to toilet and laundry. Would need a pump to pump the water and if no water then a system to manually turn on the mains again to those pipes.
Bricks, what is included in the "system" you talk about? I want to try and do this the simplest and cheapest way possible.
Cheers
McBlurter

[journeyman Mick]

McBlurter,
go to my earlier post (#2) for the simplest, cheapest way of doing it.

Mick

[totoblue]

Thanks for that. Would I actually need this or is it overkill?
I would assume all I need is some connection from the tank to the mains so water can get from tank to toilet and laundry. Would need a pump to pump the water and if no water then a system to manually turn on the mains again to those pipes.
Bricks, what is included in the "system" you talk about? I want to try and do this the simplest and cheapest way possible.

The simplest and cheapest is not to have any mains backup. If the tank runs out and you can't flush the toilet, just put some water in the tank with the hose.

If you have ever seen what comes out of a tank sometimes, you would not want it to contaminate your mains. That's what one-way valves and air-gaps are for. Since you want the cheapest and simplest way, I guess you're going to just have a leaf filter on top of the tank (like me) and that means your tank water is at times not going to be pristine. I've got a 19mm irrigation water filter to protect my pump from chunks but we only use tank water on the garden. Sometimes the water comes out brown like tea, plus other times you get rust out of the pump (unless you get an expensive stainless pump).

[totoblue]

Another thing about mains backup: if it tops up the tank automatically, it's my guess that the water in the tank is then subject to water restrictions (e.g. in Melbourne you can't water your garden 99% of the time). I haven't ever seen the details of the water restrictions in legalese but they must be somewhere, or people couldn't be penalized for breaking them.

If you have a pump-based backup like the Davey Rain-bank then I presume you could water the garden after you turned off the mains-supply line to the Rain-bank.

[Sturdee]

Another thing about mains backup: if it tops up the tank automatically, it's my guess that the water in the tank is then subject to water restrictions (e.g. in Melbourne you can't water your garden 99% of the time). I haven't ever seen the details of the water restrictions in legalese but they must be somewhere, or people couldn't be penalized for breaking them.

You're right. A few month back according to the local rag someone had their water supply restricted until their tank set up was disconnected from the mains and fined accordingly for breaches of the restrictions.


Peter.

[woodbe]

I've wondered about this too.

It seems to me that we are trying to make a simple task complicated. I'm thinking 'forget automatic switchover' Why not just put some sort of control on the tank, so that the pump won't run if the level is too low. I'm happy to switch the valves over, but I'd rather not fry the pump when we run out of tank water.

woodbe