Expert Septic System Design You Can Depend On
At Taranaki Wastewater Designers, we specialise in creating efficient, reliable septic system designs for new homes and system replacements. With a team of three highly experienced designers, we offer end-to-end expertise, combining in-depth knowledge of design and installation to ensure your project runs smoothly.
What We Do
Septic System Design
We provide compliant, site-specific septic system designs for residential and commercial developments. Our service includes assessment of soil conditions, site constraints, and future land use to determine the most appropriate treatment and disposal solution.
Learn more
Designs are completed in accordance with local council requirements and NZ standards, ensuring reliable long term performance and smooth consenting.
Storm Water Design
We design practical and compliant stormwater management solutions for residential and commercial sites. Our designs consider site layout, soil conditions, rainfall intensity, and future development to determine the most effective method of disposal or reuse.
Learn more
Options may include soakage systems, attenuation, or rainwater collection, all designed to meet local council requirements and ensure reliable long-term performance.
Soil Testing
We carry out site-specific soil testing to determine ground conditions for wastewater and stormwater design. Testing assesses soil type, permeability, groundwater levels, and site limitations to ensure systems are correctly sized and located.
Learn more
This information is critical for compliant design, reliable performance, and successful council consenting.
Council Documentation
We prepare all required documentation to support council consent applications for wastewater and stormwater systems. This includes design reports, site plans, calculations, and supporting information tailored to local authority requirements.
Learn more
Our documentation is clear, accurate, and compliant, helping to streamline the consenting process and avoid delays.
Existing System Reports
We assess and report on existing wastewater and stormwater systems to determine condition, compliance, and suitability for continued use or proposed development.
Learn more
Our reports identify system limitations, required upgrades, and any risks, providing clear recommendations to support council approvals, property transactions, or future planning.
Why Choose Us
Expertise
Fully qualified plumbers and drainlayers with design certification.
- Systems designed to meet all local council and environmental regulations.
- Deep understanding of practical installation requirements
- Regular checks during installation to guarantee compliance.
Experience
Hands-on experience in both wastewater design and installation.
- Designs that are practical, efficient, and easy to maintain.
- Avoid costly mistakes with systems that are buildable and functional.
- Peace of mind knowing your wastewater system is safe, reliable, and efficient.
Collaboration
Working alongside you from concept to completion.
- Close coordination with installers throughout the process.
- Clear, consistent communication at every stage.
- Systems delivered exactly to specification, without delays.
Connections
Strong supplier relationships that add value to your project.
- Established relationships with leading wastewater suppliers.
- Access to the latest products, innovations, and technical support.
- The right solution sourced quickly and cost-effectively.
How We Work
01
Initial Enquiry
Getting started is simple. You can reach out to us via phone or through our website to discuss your project.
02
Free 15-Minute Consultation
We offer a complimentary 15-minute consultation to review your plans and ensure our services align with your needs. This is a no-obligation opportunity to discuss your project and see how we can help.
03
Proposal & Quote
If it looks like a good fit, we’ll prepare a detailed proposal and quote for our services.
04
Deposits & Scheduling
Once the proposal is accepted, a 50% deposit is required to schedule a site visit, with the remaining 50% due before the final design is delivered.
05
Site Investigation
We carry out on-site investigations, including soil and soakage testing, to gather the information needed for an accurate design.
06
Design Compilation
After testing, we compile all findings into a comprehensive wastewater or stormwater system design. Designs are typically completed within 1–2 weeks from the date of site testing.
07
Installation
To ensure the system is installed exactly as designed, we highly recommend using our trusted installation company, Evergreen Plumbing. If another company completes the installation, additional site visits may be required, and extra charges will apply.
We Work With
Frequently Asked Questions
Do I need a septic system or can I connect to the council sewer?
If a council sewer connection is available at your boundary, most councils require you to connect to it. A septic (on-site wastewater) system is generally only permitted where no public sewer is available or connection is impractical.
What size septic system do I need for my house or building?
System size is based on the number of bedrooms (or occupants), daily wastewater flow, and site conditions. In New Zealand, designs must comply with specific standards and council requirements, which set minimum tank and disposal field sizes.
How long does a septic system last?
With correct design and maintenance, a septic tank can last 25–40 years. Disposal fields usually last 15–25 years, depending on soil conditions, loading, and maintenance.
How often does a septic tank need to be pumped out?
Typically every 3–5 years for domestic systems. Some councils require proof of regular pump-outs, especially for advanced treatment systems.
What are the signs that my septic system is failing?
Common signs include slow drains, sewage smells, wet or spongy ground near the disposal field, sewage backing up into the house, or unusually green grass over the field.
Can I build over or near my septic tank or disposal field?
No. Building over or too close to a septic tank or disposal field is not allowed. Councils require minimum separation distances from buildings, boundaries, waterways, and bores to prevent contamination and allow future maintenance.
What can and can’t go down a septic system?
Only wastewater and toilet paper should go down the system. You should avoid fats, oils, wipes (even “flushable” ones), chemicals, solvents, and excessive disinfectants, as these damage bacteria and can cause blockages.
Will a septic system work on a small section or sloping site?
Possibly, but it depends on soil type, slope, and available area. Steep or small sites often require advanced treatment systems or alternative disposal methods. A site and soil assessment is usually required.
What soil type is required for a septic disposal field?
Soils must be able to absorb and treat wastewater. Sandy and loamy soils are usually suitable; heavy clay or shallow soils may require engineered solutions such as raised beds or pressure systems.
Do I need council consent or approval for a new septic system?
Yes. A septic system requires a Building Consent and often Resource Consent. Councils require a professional design and soil assessment before approval.
Do I need a stormwater system or soakage on my property?
Yes. All buildings must manage roof and surface water so it does not cause flooding, erosion, or nuisance to neighbours. This is required under the NZ Building Code (E1 Surface Water).
How do I know if my site is suitable for stormwater soakage?
A soakage test is usually required. This measures how quickly water can soak into the ground. Clay soils, high groundwater, or rock can make soakage unsuitable.
What size stormwater system do I need?
System size depends on roof area, rainfall intensity, and ground conditions. Councils specify design storm events (often 10-year or 20-year storms) that must be catered for.
What happens if soakage is not viable on my site?
Alternative solutions may include detention tanks, pumping systems, or connection to council stormwater mains (if available and approved).
Can stormwater be connected to the council main?
Only if a council stormwater connection is available and permitted. Approval is required, and in many areas, on-site soakage is preferred or required instead.
What are the rules around stormwater discharge on my property?
Stormwater must not discharge onto neighbouring properties or cause erosion, flooding, or damage. Councils require controlled disposal within your property or an approved outlet.
How do I manage stormwater on a sloping or clay site?
Sloping or clay sites often need larger soakage systems, detention tanks, or engineered solutions to slow water and prevent runoff or instability.
What is the difference between stormwater and wastewater systems?
Stormwater handles rainwater from roofs and surfaces. Wastewater systems (septic) handle sewage from toilets, showers, and sinks. They must be completely separate and never connected together.
How long does it take to design and get approval for a system?
Design usually takes 1–3 weeks, depending on testing and site access. Council approval can take 2–6 weeks or longer, depending on whether resource consent is required.
How much does a septic or stormwater system typically cost?
Costs vary widely depending on system type and site conditions.
As a rough guide in NZ:
- Septic systems: $12,000 – $35,000+
- Stormwater systems: $3,000 – $15,000+
A site-specific design is needed for accurate pricing.