By Sarah Chen · environmental engineer · water, waste and everything that flows downhill
“After losing three days of water to a 200-litre tank that was simply too small, I now size pressure vessels for every drop that falls.”
— Sarah. Every litre accounted for.
ArticlesCalculatorsSite PlannerShopLook, if you're off-grid in Australia and you've got a pump, you need a pressure tank. No tank? Your pump will crap itself in 3 months. Done. Let's get to sizing.
Look, if you're off-grid in Australia and you've got a pump, you need a pressure tank. No tank? Your pump will crap itself in 3 months. Done. Let's get to sizing.
Your pump's job is to push water. Without a tank, it cycles on/off every 5 seconds. That's 1,000+ starts per day. Pumps don't like that. They die. You get a $200 pump and a $500 tank? Yeah, we've seen it. Tank saves your pump. Period.
Forget "bigger is better". You want the smallest tank that won't make your pump crap itself. Rule of thumb: 10 litres of tank per 100 litres of daily water use.
Example: If you use 200L/day (typical for 2 people), get a 20L tank. Done. No need for 100L. You'll just waste money and space.
Stupid mistake: People buy 100L tanks because "it's cheap". Then they wonder why their pump runs 24/7. Tank too big = pump runs constantly. Tank too small = pump cycles like a madman. Find the middle.
Drawdown = how much water you can actually use from the tank before the pump kicks in. It's not the tank size. It's the usable volume.
Example: A 20L tank with 50% drawdown = 10L usable water. That's why you need the right tank size. If you use 10L in one go (shower), the tank empties. Pump kicks in. You get a 10-second break. Perfect.
Drawdown depends on:
Set your pressure switch wrong and you'll either:
Australian standard settings:
Set it to 40/60 PSI. That's it. Don't overcomplicate. If your pump runs constantly, raise the cut-in. If no water, lower it. Done.
Practical tip: If your tank is 20L, 40/60 PSI, and you have a 10L shower, you'll get 10L before the pump kicks in. That's why sizing matters. Too small tank = shower stops mid-flow. Stupid.
Pump & Tank Co (NSW): 20L bladder tank + pressure switch. $249. Includes setup guide. Best for small off-grid setups. No bullshit.
Link: pumpandtankco.com.au/offgrid-tanks
Rural Water Solutions (QLD): 30L tank. $320. Good for 3-4 people. They'll tell you exactly what you need. No upsell.
Link: ruralwatersolutions.com.au/tanks
Bunnings (Nationwide): Generic 20L tank. $199. Don't buy this. It's a $200 mistake. Poor drawdown, pump dies faster. Save your money.
Price: $199 (but you'll spend $500 on a new pump later)
Size your tank right. Set the pressure right. Buy from a supplier who knows off-grid. Don't be the bloke with a pump that's screaming 24/7. It's not hard. It's not expensive. Just do it.
Last updated: June 2023. Prices sourced from Australian suppliers. No affiliate links. Just facts.
While many off-grid projects are achievable as DIY, certain situations require licensed professionals:
Always check local regulations and obtain necessary permits before commencing work.
Worth a watch: Off Grid Water Pressure Tanks · The Ready Life