How Large Should Your Water Tank Be If You Move Off the Grid?
If you're moving off the grid, you need to bring water, and in most cases, that means investing in a water tank. But, how much do you need? Should you get a 10000 litre water tank? Larger? Smaller? The right answer varies, but here's what you need to consider.
Health Needs
First and foremost, think about how much water you and your family need to stay alive and healthy. From a health perspective, most men need 2.6 litres of water per day, and women need 2.1 litres. That means if you're moving off grid and there are three women and two men in your group, you need a minimum of 5.2 litres for the men and 6.3 litres for the women or 11.5 litres total per day.
Washing
Next, consider basic hygiene. You may want enough water for long baths or showers every day, or you may just want a few litres for handwashing during the day and enough water to fill a barrel for a weekly bath. As you make your estimates, remember to allot at least a few litres of water for washing dishes every day and some for washing clothing, and most importantly, remember that if you set your estimates low, you have to stick to those amounts. If you constantly go over your allotment, you won't have enough water in your water tank.
Cooking
You may also want some water for cooking. Take a week or so, and watch yourself cook. Make notes on how much water you use, and use that information to help you determine which size of water tank you need.
Waste Disposal
Are you going to have flush toilets at your off-the-grid home? If so, you need to allot water for that as well. If you embrace the "if it's yellow, let it mellow, if it's brown flush it down" philosophy, you won't have to flush as much, but you still need to allot for one to two flushes per person per day. The most economical toilets in Australia use about 3.5 to 4 litres for every flush. If you plan to use a compost toilet you can skip this step.
Gardening
If you're going to garden, you should also consider the water you need for that. However, you may want to invest in two water tanks: one for indoor use and potable water and the other for rainwater harvesting and gardening. That requires you to invest in two water tanks upfront, but over time, it can save you money.
Finally, you may want to consider your current usage. When you're ready to buy or if you have more questions, contact someone who sells water tanks.