Residential
What is this booklet about?
Home wastewater systems are used on properties that are not connected to Council’s sewer. In the Gisborne district it’s all areas outside Gisborne city, Te Karaka, and Te Puia townships. It includes Wainui beach, Makaraka, and rural and coastal areas.When it works well, managing your own waste is as easy as collecting your own rain water, but if something goes wrong, it can be unpleasant and expensive to fix. This booklet is for people who use or need to install an onsite wastewater system – commonly referred to as a septic tank – and will help you get it right from the start.
Contents
Onsite wastewater systems
3
Types of systems
3
How the system works
4
Installing an onsite wastewater system
5
Wastewater treatment professionals
6
Legislation and resource consent
6
Exempt work
6
Looking after your system
6
If things go wrong
7
Costs 7
Find a wastewater specialist
8
Approved site assessors/system designers
8
Tank cleaning specialists
9
Onsite Wastewater Systems
Onsite wastewater systems are used to dispose of all household waste that goes down the drains or toilet. With an onsite wastewater system, there is no ‘flush and forget’ – all your liquid household waste has to be safely and hygienically processed on your property, in your wastewater system, which itself is a living system. An effective system contains and processes waste without contaminating ground water or surface water, or having adverse affects on the environment.
Types of systems
There are two main types of onsite wastewater systems:
` one or more septic tanks with a gravity or pumped effluent disposal bed
` a home treatment system that usually has dripper line disposal. Your wastewater system may include:
` sanitary plumbing fixtures connected to drain pipes that take sewage and sullage – that’s the liquid from kitchens, wash basins, toilets and laundries – to the septic tank
` treatment tanks – passive, aerated or filtered
` a distribution system, pump, siphon, or gravity fed
How the system works
The type of system you install will depend on your property. Most systems work in a similar way in that wastewater is gradually separated, treated, and dispersed – with the help of an army of natural organisms. Just as we have ‘good bugs’ in our stomachs, septic tanks have anaerobic bacteria that partially breaks down solid waste. Your septic tank depends on these organisms to work properly, which is why you must keep your septic tank a chemical free zone.
When you flush the toilet or run the tap, sewage and sullage flow to the septic tank where the solid matter settles on the bottom and forms sludge, while fats and lighter matter float to the surface to form a scum.
Figure 1 - Conventional Septic Tank
Scum Zone
Settling Zone
Sludge Zone
To land application trenches or bed All household waste
waters (excluding rainwater)
Filter if required
Inspection Cover - must be above ground level
The intermediate liquid that has had most of the organic matter digested by your tank’s ‘bugs’ is eventually discharged into an ‘effluent trench’ – a series of underground pipes on a gravel bed used to evenly dispose of treated wastewater. While it soaks away it is further treated by organisms that live in the drainage metal and soil.
Disposing of any kind
of chemicals – paint,
disinfectant, petrol,
flammable liquid,
bleaches – down your
drains or toilets can
wipe out the organisms
your tank needs to work
properly.
Figure 2 - Septic Tank and Effluent Trenches Pump Chamber (if required) Septic Tank Distribution Box Effluent Trench Approved Effluent Metal Unexcavated
The effluent trench is dug deep enough for treated wastewater to safely soak into the ground without contaminating the groundwater. The trench is lined with clean washed river metal, with the pipe laid flat with more river metal . A textile filter cloth is laid over the metal before backfilling to prevent the downward movement of soil that could clog the drainage metal. The top of the trench system must be crowned to stop rainwater pooling.
Figure 3 - Conventional Trench System
Filter Cloth Perforated Pipe Distribution Aggregate (20 - 70 mm) 600mm 100mm 75mm min Existing Surface Crowned Finished Surface
Topsoil
Installing an onsite wastewater system
If you’re installing a new system, it’s important that the tanks and effluent beds are the right size so they have the time and area to work efficiently. Talk to a professional about the best type of system, and the best size and location, for your property.
WASTEWATER TREATMENT PROFESSIONALS
The Council maintains a list of approved people who do site assessments and design for onsite wastewater systems in the Gisborne district. They can evaluate the soil type and soak rate, and use a set of guidelines to design a system that will suit the building and the property, and protect the surrounding environment.
In general, installing a septic tank or effluent disposal system will require some degree of site evaluation and design before a building consent can be issued. You will need to provide details of this work, such as a site plan and details of the system type, size and layout, with your building consent application. The Council will only accept it if it has been done by one of the assessors listed at the back of this booklet, or a recognised wastewater engineer.
Legislation and resource consent
Onsite wastewater systems must meet the environmental standards in the Resource Management Act and the Gisborne Regional Discharges Plan. They must also meet the functional and durability requirements of the New Zealand Building Code and the Building Act.
To install a new system or replace a failed system you’ll need a site assessment and building consent. The site assessment is to be carried out by an approved assessor, who will design a system or identify the work required to rectify the failure. Or you can use a recognised wastewater engineer to design a system. The design must be based on the site assessment.
EXEMPT WORK
Some like-for-like building maintenance projects don’t need a building consent under exemptions in Schedule 1 of the Building Act. Although replacing a failed effluent line is included in the examples in the schedule, it is likely to still need a building consent. A failed system won’t comply with the regional rules under the Discharges Plan and therefore the like-for-like option does not apply.
Looking after your system
These tips will help to keep your septic tank working safely and reliably.
` Desludge every three to five years or when scum and sludge take up two thirds of the tank – or the first stage of a two-stage system
Problems can arise when systems aren’t maintained and when absorption areas get blocked or clogged. Look out for:
` wet or soggy absorption field with wastewater ponding on the ground
` a bad smell near the septic tank or absorption area
` drains and toilets run slowly
` grease trap is full or blocked.
If things go wrong
A failed onsite wastewater system is a serious health and environmental hazard and can lead to:
` the spread of infectious disease
` an increase in mosquitoes, flies and rodents
` pollution of waterways, beaches, streams and shellfish beds
` contamination of bores, wells and groundwater
` alteration of local ecology
` air pollution and odours.
Regularly cleaning and maintaining your system will help to prevent costly failures.
Costs
It can cost between $15,000 for a small basic septic tank system to around $22,000 or more for a more complex system (2014 costs). Transport costs to remote sites could add significantly to these costs.
The cost of cleaning your tank can also vary depending on where you live. This is because contractors charge for mileage to and from your property.
Systems that have been installed since 2002 may have a filter on the outlet from the second tank or chamber. These must be cleaned regularly or the filter will clog and cause backups in the tank.
Systems with a pump, aerated home treatment plants (AWTS), and low pressure dosed effluent systems have ongoing power costs. An AWTS needs bi-annual maintenance. All maintenance is at the homeowner’s cost.
For comparison, all single residential properties in Gisborne city that are connected to the main sewer line pay about $560 a year . This is on top of the original connection costs, which depend on the distance between the house and the main sewer line. Over the life of your septic tank , reticulated and tank costs are comparable.
Find a wastewater specialist
APPROVED SITE ASSESSORS/SYSTEM DESIGNERS
Andrew Appleby or George Winkler LDE PO Box 671, Gisborne P M F E (06) 8673035 027 4989 636 (06) 8673037 info@lde.co.nz Gary Thompson Thompson Drainage 81 Innes street, Gisborne
P M E (06) 867 4902 027 445 9720 thompsondrainage@xtra.co.nz John Taylor
Terry Taylor Drainage
89 Customhouse Street, Gisborne
P F E (06) 868 5383 (06) 868 5386 terrytaylor@xtra.co.nz Ian Donaldson Donaldson Plumbing 73 Carnarvon Street, Gisborne
P M E (06) 863 3688 027 435 921 idonaldson@vodafone.co.nz Alan Hall 8 Ferry Road RD 1, Gisborne P F (06) 862 5597 (06) 862 5598 Carl Horne
834 Gladstone Road, Gisborne
P M E (06) 8681543 021 903 061 carlandtech@xtra.co.nz Sarah Millar Evironmental Engineer
Opus International Consultants Ltd
P M E W (06) 868 5199 021 240 5541 Sarah.Millar@opus.co.nz www.opus.co.nz
The use of any firms or people listed in this booklet is for the information and convenience of the reader. Such use does not constitute an official endorsement or approval by the Gisborne District Council of any product or service, that they provide or to the exclusion of others that may be suitable.
You may use your assessment to get quotes from a number of drain layers and are in no way obliged to use the drain layer who carried out the assessment.
TANK CLEANING SPECIALISTS
Below are some local service agents who offer septic tank cleaning in Gisborne. Regularly cleaning your tank will help to keep your system working well.
Agent Contact details
Wayne’s Waste (06) 867 3606 Terry Taylor Drainage (06) 868 5383 Baywaste/Envirowaste (06) 868 6007
Morris Mataira (06) 864 8359 (Ruatoria) Septic Solutions Ltd (06) 864 4831 ( Te Araroa) Fulton Hogan (06) 869 1825
MAINTENANCE AND SERVICE AGENTS
There are several companies and agents in Gisborne that offer tank maintenance services.
Type of wastewater system
Recommended
servicing frequency Agent contacts
Bio-Cycle Oasis Clearwater 6 monthly 6 monthly M P E Gary Hills 027 246 2715 (06) 868 5582 thewatertankman.co.nz Bio-Cycle 6 monthly P E Thompson Drainage (06) 867 4902 thompson.drainage@xtra.co.nz General servicing M P E
Brian Rofe Plumbing 027 2416850 (06) 8675292 brofe@xtra.co.nz KiwiTreat 6 monthly
P
KiwiTreat Limited (Rangiora) (03) 312 5787 Biolytix Aquablue Devan Blue Annually 6 monthly 6 monthly P E
Donaldson Plumbing Limited (06) 863 3688
Type of wastewater system
Recommended
servicing frequency Agent contacts
HYNDS Lifestyle 6 monthly
P E
Terry Taylor Plumbing Ltd (06) 868 5383 terrytaylor@xtra.co.nz M E Carl Horne 021 903 061 carlandtech@xtra.co.nz Innoflow - Advantex Annually
P E Walters Plumbing (06) 867 3065 waltersplumbing@xtra.co.nz AirTech 9000 6 monthly M P
Steve Wolters Plumbing 027 483 9663 (06) 868 8335 Enviroflow 6 monthly M Ross Brown 021 081 0223 Gould Tanks 6 monthly
P
Contact Council for advice (06) 867 2049
Septech Turbo Jet 2000 Annually Watercycle Annually
Find out more
15 Fitzherbert Street, Gisborne
phone
06 867 2049
emailservice@gdc.govt.nz
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