How to choose a pump and flow rate
When you choose a pump, you need to figure out how many devices or appliances that use water might be operating at the same time. This is commonly referred to as ‘taps.’ For example, three taps could mean your washing machine, a kitchen faucet, and someone using a shower or outdoor hose simultaneously.
To determine the correct pump flow rate, you must consider the distance from the water source to your pump and from the pump to the outlets in your home. Elevation, pipe size, and bends in the plumbing system can all reduce the flow rate. This is known as system friction head loss. Calculating these factors is essential to ensure your water systems provide the proper flow and steady water pressure.
What are the benefits of a pressure tank or controller?
A pressure tank will:
Use less power and improve system efficiency
Reduce pump wear and tear by eliminating unnecessary starts
Prevent premature pump failure caused by short cycling. (Dripping taps/tap being turned on and off quickly)
Reduce the risk of pump damage from water hammer by buffering sudden pressure spikes
Provide a buffer of stored water so the pump doesn’t need to start immediately every time you turn on a tap
A controller will:
Protect the pump from damage using dry-run protection
Let you adjust the start pressure (some brands adapt automatically)
Protect the plumbing by regulating pressure
Be compact and easy to install
Provide constant, reliable pressure
We recommend the use of a water hammer arrestor with any system, especially with filter systems and UV. Pumps should also always be protected from power surges with a reliable power guard.
What size tank should I get?
For most average-sized homes, we recommend a pressure tank size of at least 50L. As a rule, a larger tank is better because a water pressure tank reduces the frequency of pump starts and stops.
A tank doesn’t deliver its full volume as usable water. Only about a third of the total tank volume is available between pump cycles. This usable amount is called the drawdown capacity. The more drawdown your tank has, the fewer times your pump needs to cycle, which extends pump and bladder life.
How to properly size your tank:
Use this simple rule: Drawdown needed = pump flow rate (LPM) x minimum run time (minutes). Most manufacturers recommend at least a one-minute run time to avoid short cycling.
For example, if your pump delivers 40 LPM and you want at least one minute of run time, your tank should provide about 40L of drawdown. Since only one-third of the tank volume is usable, you’d need a tank of roughly 120L.
The bladder in a tank is typically rated for tens of thousands of cycles, and fewer pump cycles generally extend its lifespan.
Average water requirements:
- Cottage or Bach: 1 bathroom — 1-2 taps
- 15-20 litres per minute
- Small Home: 1 bathroom, single-storey — 2+ taps
- 30-40 litres per minute
- Typical Home: 1-2 bathrooms, single-storey — 3-4 taps
- 40-50 litres per minute
- Larger Home: 2 bathrooms, 2-storey — 4+ taps
- 50-70 litres per
- Large Home: 2+ bathrooms, 2-storey, multiple appliances — 5+ taps
70-110 litres per minute
- Large Building: Multiple bathrooms, appliances and levels — 6+ taps
- 90-250 litres per minute
Note: These figures are indicative. Actual requirements depend on your pump and plumbing system.
Choosing the correct size tank for your water demand ensures optimal performance and prevents premature wear.
What maintenance do I need to do?
Check the pre-charge every 6–12 months; re-pressurise only if needed. If it’s more frequent, the bladder may need re-pressurising or replacement. With Trade Tested’s tanks, you can buy a pressure tank bladder at a much lower cost than replacing the entire unit.
Steps to replace a bladder:
- 1. Isolate power to the pump and shut off the water supply. Drain the tank fully
- 2. Release any remaining air using the pressure relief valve
- 3. Undo the unit at the base. The bladder should slide out easily
- 4. Wipe and dry the inside of the tank thoroughly to prevent surface rust
- 5. Insert the new bladder, close the unit, and re-pressurise. Always set the pre-charge to 2 PSI below the cut-in pressure of your pressure switch for correct operation
Get the right pressure tank for your water system
Shop online or in-store today to discover our full range of high-quality tanks, jet pumps and parts & accessories to keep your system running efficiently. If you have any more questions, just give us a call 0800 800880 or send us an email.
Real customer reviews & testimonials
Hyundai Pressure Tank Vertical 24L
“The pressure tank saves my off-grid system from having to turn the pump on each time I use a tap! I therefore use far less of my battery storage. Definitely recommend this.”
“This was a five-minute fix, and our pump is a lot happier not switching on and off as much.”
“Perfect for our situation, as all our house supply water is pumped. Saves on power as it can do up to 4 toilet flushes before the pump kicks in. Excellent value for money.”
“Great product, good size allows my pump to not come in until the tap has been running for a while.”
FAQs about pressure tanks
How does a pressure tank work?
A pressure tank works by using compressed air to maintain steady pressure in your system. As water enters, the air compresses, creating the pressure needed to push water through your plumbing system.
What happens if my pressure tank is too small?
An undersized tank will lead to frequent cycling, shorter pump run time, higher energy costs, and possible premature failure. Purchasing a larger tank will help maintain stable water pressure by reducing pump cycling and preventing sudden pressure drops during use.
How do I set my pressure switch?
We recommend a cut-in and cut-out pressure setting that matches your needs. For example, a common setting is 30/50 PSI, but higher-demand homes may use 40/60 PSI. When adjusting your pressure switch settings, make sure the tank’s air pressure is set to 2 PSI below the pump’s cut-in pressure. Always use a reliable pressure gauge to monitor accuracy.
Can I use the same tank for home and irrigation systems?
Yes. Many homeowners use one pressure tank to support both indoor and outdoor systems. Just ensure the tank has sufficient drawdown capacity to avoid rapid cycling when sprinklers run.
Do I need a pressure tank if I’ve got an electronic controller?
Many controllers can operate without a tank, but adding even a small tank reduces cycling and smooths system pressure, especially with low/variable flows.
How do I know if I need a new pressure tank
Signs include inconsistent water flow, loss of pressure, visible leaks, or the pump turning on and off too frequently. If water pressure builds erratically, it’s often time for a new tank.
I can buy a cheap tank, are these ok?
Yes, but only if it’s safe for drinking water. The bladder must be EPDM rubber, and all potable-water contact components should comply with AS/NZS 4020 standards. Many cheap tanks use non-EPDM rubber, which can leach chemicals into your water. All Trade Tested bladders are certified EPDM, and our tanks are built for safe drinking water and long-term performance. So, you’re in the right place.
