How big a septic tank do I need NZ?
Andrew Henderson
Updated on March 17, 2026
How big a septic tank do I need NZ?
Your on-site sewage system needs to be big enough to deal with all of your house’s wastewater – an average New Zealander uses 160–250 litres of water a day. For a three-bedroom house, you’ll need a tank with at least 3000 litres’ capacity. Some councils require at least this size.
What is the standard size of septic tank?
Length of septic tank (L) should be taken as 9feet 9 inches or 9.75 feet. Breadth of septic tank (B) should be taken as 6 feet 3 inches or 6.25 feet. The standard height (D) of septic tank should be taken as 5 feet 9 inches or 5.75 feet.
How do I determine the size of my septic tank?
Septic Tank Size Calculation based Per User Consumption
- Cooking – 5 Liters.
- Bathing & Toilet – 85 Liters/Person, So for 5 person – 425 liters/Day.
- Washing cloths & Utensils – 30 Liters.
- Cleaning House – 10 Liters.
- Other – 5 Litres.
How often should a septic tank be emptied NZ?
every 3-5 years
Tanks generally need pumping (cleaning out) every 3-5 years to remove sludge and sediment.
How close can a septic tank be to a house NZ?
Our answer: We recommend a distance between the septic tank and the treatment unit of 1 metre in our instructions, in order to leave ample work space for installing the connections. Otherwise a depth of fill of 30 cm should be adhered to.
How big should a septic tank be for a 4 bedroom house?
Minimum Septic Tank Capacity Table
| Number of Bedrooms | Minimum Septic Tank Size | Minimum Liquid Surface Area |
|---|---|---|
| 2 or less | 1000 – 1500 Gallons | 27 Sq. Ft. |
| 3 | 1000 – 2000 Gallons | 27 Sq. Ft. |
| 4 | 1250 – 2500 Gallons | 34 Sq. Ft. |
| 5 | 1500 – 3000 Gallons | 40 Sq. Ft. |
How do you calculate septic tank size and septic tank?
Space above liquid level is 0.3m depth. So the volume of space above liquid level is 2.76m2 X 0.3 = 0.828m3. Hence, total volume of septic tank for 20 person with a sludge clearance period of one year is = 0.828 + 0.64 + 1.46 + 0.828 = 3.756 m3 .
How do I calculate the size of my septic drain field?
Drainfield Size
- The size of the drainfield is based on the number of bedrooms and soil characteristics, and is given as square feet.
- For example, the minimum required for a three bedroom house with a mid range percolation rate of 25 minutes per inch is 750 square feet.
Are long showers bad for septic systems?
Washing frequent, small loads of laundry or taking exceptionally long showers every day is all it takes to overload your septic system with too much water. The primary treatment tank needs time to break up solids before partly-treated water can enter the drain field.
Who pays to empty septic tank?
Homeowners. If you’re an owner-occupier and your property has a septic tank, it’s very straightforward: you are fully responsible for your septic tank. If there are any issues with it, it is up to you to fix them.
Do you need a permit for a septic tank NZ?
You will need a building consent, and you may need a resource consent to install a new wastewater system or to make proposed alterations to that system. The consents ensure the system complies with the building code and doesn’t endanger the environment or public health.
Can a septic tank be too big?
A septic tank that is too big will not run well without the proper volume of wastewater running through it. If your septic tank is too big for your house, there wouldn’t be sufficient collected liquid required to produce the bacteria, which helps break down the solid waste in the septic tank.
What is a septseptic tank?
Septic tanks provide a simple, practical and efficient on-site alternative for managing household sewage disposal. The Pump Chambers are made from high strength polyethylene and are designed and manufactured in New Zealand. They have been specially designed for domestic applications where a property is below the conventional council sewage line.
Why choose Promax septic tanks in New Zealand?
When it comes to septic tanks in New Zealand, there is no room for compromise. Hygiene and safety are paramount, and the structural integrity of the tank has to be flawless. That’s precisely what you get in every Promax septic tank.
What is a domestic septic tank?
They have been specially designed for domestic applications where a property is below the conventional council sewage line. The chambers are certified to both AS/NZS 4766 – polyethylene storage tanks for wastewater and chemicals and AS/NZS 1546.1 – on site domestic wastewater treatment facilities.
Where can I find more information about septic tank treatment?
Look under Septic Tanks, Water Treatment, or Water & Wastewater Services in the Yellow Pages. Protect the soakage treatment area so that the effluent leaving the tank has best conditions to disperse or evaporate.
