Supporting heavy stuff

I would use 6x6's for the legs notched on 2 sides to support the rails. That way solid woods supports the rails rather then screws.

Collecting rain water in Australia is big business. We have three water tanks for our house. Two sit directly on a concrete slab, the other sits on levelled gravel. Rain water makes the best cup of tea. Uses less soap for laundry and feels great when showering. Yes really. I will take some pics to prove it. Down sides. Keeping gutters clean, replacing filter's often. 
But it's worth it and water is a very valuable resource. Rain water is much better for vegetable beds and fruit trees.
Nice set up. I'm thinking of buying wine barrels to store water at the new house.
Cheaper than plastic if you can believe that.

Not even outdoors ? 
Come on man. It'll be just like MASH.
Only bigger.

That's not a rainwater tank !

This is a rainwater tank.

If you mount water tanks on wood eventually the weight and damp will eat the structure alive. Don't waste your money on concrete slabs either like this one. 
Nowadays everyone creates a level with coarse gravel and calls it good. The gravel provides good drainage too. 
Let gravity do the hard yards for you. The outlet is usually 5" above the bottom so that the weight of remaining water stops the tank getting blown away by heavy wind. It also acts as a sump for the inevitable sludge build up. Every six year's or so we take off the lid, tip the tank over and hose out the junk. Easy. It's what Taylor Swift would do down under. 
This is a typical set up for country homes.
Our other tank is fibreglass. Much bigger. We gravity re fill it from these two.

How come no wells? I am in USA, CT and I have what is called a shallow well. It is 95 feet deep. The pump is in my basement which helps when maintenance is needed.

Ralph Lipeles wrote:

How come no wells? I am in USA, CT and I have what is called a shallow well. It is 95 feet deep. The pump is in my basement which helps when maintenance is needed.

We have a well but down under they are called Bores. Bore water quality varies widely. Some are to salty, some have to much iron, some have excess of certain minerals like manganese that make them unpottable. We had a well when we lived in America. Bit high in copper but good drinkable water.
Here our bore water is drinkable only after settling for a month or two to let the minerals settle out. 
Rain water is preferred but if we have to we use the bore water. 
In Oz, bores are a lottery. You could hit exceptional water or sulphur smelling iron laden crud. Salt is often a problem. 
We hit good quality but low volume. 
The problem in America is more likely pollution. Nitrates, PCB, pesticides.

admin wrote:

@Maurice,

How do you filter out the bird poop from the roof rainwater?

You don't. You suck it up princess. Or you get one of them there fancy UV light sterilisation do Hickeys. 
Me ? I just spit out the large chunks on to the veggie patch and use the rest to gargle. It's cheaper than Listerine and has a pleasant discouraging effect on tax inspectors. You should try it. 
Down under you get tough real quick or die from spider bites and cold hearted Aussie women. It's kinda like Ohio with the gloves off.