I've spent a lot of time looking at water storage lately, and honestly, a 600 litre tank seems to be that perfect "middle ground" size for most people. It's not so big that you need a crane and a construction crew to install it, but it's significantly more useful than those tiny 200-litre rain barrels that run dry after a single afternoon of watering the garden.
If you're sitting on the fence about what size to get, it helps to visualize what 600 litres actually looks like. Think about six large bathtubs filled to the brim. That's a decent amount of weight—about 600 kilograms (not counting the weight of the tank itself). It's a serious bit of kit, but it still fits into the corner of a patio or down that narrow side-passage of your house that usually just collects old flower pots and spiderwebs.
Why the 600-litre size is the sweet spot
Most of us start our water-saving journey with a small barrel under a downpipe. It feels great for the first week, but then a dry spell hits, and you realize you've used the whole lot on your tomatoes in about forty-eight hours. On the other end of the spectrum, you have those massive 5,000-litre behemoths that look like something from a water treatment plant.
The 600 litre tank sits right in the Goldilocks zone. It's small enough to be manageable for a DIY setup, yet it holds enough volume to actually make a difference when the weather gets a bit crisp and dry. You can comfortably water a medium-sized vegetable patch for a week or two without breaking a sweat. Plus, from an aesthetic standpoint, they tend to be designed with a slimmer profile these days, so they don't have to be an eyesore.
Thinking about the footprint and placement
Before you go out and buy one, you really need to think about where it's going to live. Since a full 600 litre tank weighs over half a ton, you can't just plonk it down on some loose soil or a few wobbly bricks. If the ground shifts, the tank can tilt, crack, or—worst case scenario—fall over.
I always tell people to prep a proper base. A level concrete pad is the gold standard, but some well-compacted gravel or a set of heavy-duty paving slabs can do the trick too. Just make sure it's dead level. If it's even slightly off, the pressure on the walls of the tank won't be even, and that's how you end up with leaks a few years down the line.
Also, consider the height. If you aren't planning on using a pump, you'll want the tank slightly elevated so gravity can do the hard work for you. Getting a watering can under the tap is much easier when the tank is sitting on a sturdy stand.
What can you actually do with 600 litres?
You'd be surprised how quickly you can go through water, but also how much you can accomplish with 600 litres. For the average gardener, this is plenty for keeping your "high-value" plants alive—the stuff in pots, the greenhouse crops, and the freshly planted shrubs.
But it's not just for the garden. A lot of people are starting to use a 600 litre tank as a basic emergency backup. If your local water main bursts (which seems to happen more often than it used to), having 600 litres of non-potable water on hand is a lifesaver. You can use it to flush toilets, wash your hands, or even "sponge bath" if things get really desperate. It provides a massive sense of security knowing you aren't completely dependent on the grid for every single drop.
Rainwater harvesting basics
If you're using your 600 litre tank for rainwater, the setup is pretty straightforward. You'll need a diverter kit that connects your house's downpipe to the tank. The cool thing about these kits is that once the tank is full, the water just bypasses the tank and goes back down the drain like it normally would. No overflowing, no soggy foundations.
One thing I've learned the hard way: get a good filter. Leaves, twigs, and the occasional adventurous bug will try to make their way into your tank. Without a screen or a filter, all that organic gunk settles at the bottom and turns into a bit of a smelly sludge. A simple mesh screen at the inlet makes a world of difference.
Choosing the right material
You'll mostly see two types of tanks in this size range: plastic (usually high-density polyethylene) and metal (often galvanized steel).
Plastic is the most common for a 600 litre tank because it's light, won't rust, and is usually cheaper. It's also easier to move around if you realize you've put it in the wrong spot. Just make sure the plastic is UV-stabilized. If it's not, the sun will eventually make the plastic brittle, and it'll start cracking after a few summers.
Steel tanks look a bit more "industrial-chic" and are incredibly tough. They're great if you live in an area prone to bushfires or if you just prefer the look of metal over plastic. They do cost more, though, and they're a bit more of a permanent fixture once they're in place.
Maintenance is easier than you think
I think some people get put off by the idea of "maintaining" a water tank, but it's really not a big deal. Once a year, usually in the autumn before the heavy rains start, I like to give everything a quick check.
Check the taps and seals for any drips. If you see algae growing inside (which can happen if the tank is a lighter color and lets in sunlight), you might need to give it a quick flush. But generally, if the tank is opaque and the lid is on tight, the water stays surprisingly clean.
If you notice the water starts to smell a bit "funky," it's usually because some debris got past your filter. There are safe, bio-friendly treatments you can drop in there to clear things up, but honestly, preventing the dirt from getting in there in the first place is the best strategy.
Is a 600 litre tank worth the investment?
When you look at the price of water these days, and the increasing likelihood of summer hosepipe bans, a 600 litre tank starts to look like a very smart investment. It's one of those things where you pay a bit upfront, but it pays you back every time it rains.
Beyond the money, there's a real satisfaction in using "free" water. There's something that feels inherently right about catching the rain that falls on your own roof and using it to grow your own food. It connects you to the seasons a bit more. You start looking at a rainstorm not as a reason to stay indoors, but as a "free refill" for your tank.
Wrapping it up
Whether you're looking to save some money on your utility bills, trying to be a bit more eco-friendly, or just want to make sure your roses don't die during a dry spell, the 600 litre tank is a fantastic choice. It's big enough to be useful but small enough to be practical for the average backyard.
It's a simple, low-tech solution to a very modern problem. Just make sure you prep your base, buy a decent diverter, and maybe get a sturdy stand. Once it's all set up, you'll wonder why you didn't do it years ago. It's one of those home improvements that just keeps on giving, rain or shine.