Maintaining your on-site sewage system
A poorly-maintained on-site sewage system is a serious health hazard.
On-site sewage systems such as septic tanks need regular maintenance - some that you can do yourself, and some that you’ll need professional help with.
Why maintain?
Health
Maintaining your on-site sewage system is important for the sake of your health and the health of others in your neighbourhood. A poorly-maintained system can contaminate bore water, groundwater, and waterways, potentially spreading infection and disease.
Household wastewater may contain:
- viruses which can cause illness such as viral gastroenteritis or hepatitis A
- bacteria such as campylobacter and salmonella
- protozoa such as giardia and cryptosporidium
- worms such as hookworms and roundworms which can cause fever, aches and chills.
Wastewater may also contain pollutants such as nitrates and phosphates which can cause toxic algal bloom in waterways.
Legal
You have legal obligations if you have a property with an on-site sewage treatment system. Even if you rent the property you live in, it will generally be your responsibility to keep the system maintained in safe working order.
You cannot legally sell or rent your property if the on-site sewage system is not operating correctly.
If you contaminate your own, or neighbouring properties and waterways, you can be prosecuted.
If you develop your property by adding another dwelling or adding to the existing dwelling, you must comply with the rules covering sewage treatment. If your soakage treatment area is built over or disturbed, and you do not rectify it, you may be liable to prosecution.
Don’t overload your system
The best way to keep maintenance to a minimum is not to overload your on-site sewage system with too much wastewater.
Most of your wastewater comes from your washing machine, toilet and bathroom. It’s possible to reduce this load on your sewage system by re-using greywater, using a waterless toilet, or simply by cutting down on your water use (see easy ways to save water).
Upgrade if necessary
If you’ve reduced your water use and your on-site sewage system still isn’t coping, you’ll need to consider an upgrade.
Multi-chamber on-site sewage treatment systems can be added to existing single septic tanks to increase capacity and speed up the sewage treatment process. Or, your soakage treatment area may not be big enough or sufficiently well-drained to cope.
Seek expert advice to determine where the problem is. Look under Water Treatment, Water & Wastewater Services, or Septic Tanks in the Yellow Pages (www.yellowpages.co.nz).
Be careful what you put into the system
What you put into your on-site sewage system will determine how much maintenance it needs. To keep it working effectively:
- Don’t do a number of loads of laundry in one day.
- Don’t empty large quantities of water into the system all at once, such as from swimming and spa pools.
- Don’t let rainwater into the system.
- Don’t put chlorine bleaches or other strong chemicals, engine oils, coffee grinds, tea bags, tissue of more than two ply, disposable nappies, tampons, paints, dental floss, stick plasters or foodstuffs into the system - these things will make the system less efficient and can stop it from working at all, which means you’ll have unsafe effluent discharged into your soakage treatment area.
- Don’t put anything toxic into it because the toxins will impair the effluent treatment process and may end up in your soil unable to be broken down.
Don’t go into the tank!
Your on-site sewage system contains toxic gases that could kill you. Never enter a septic tank yourself, and never leave the access hole open.
Regular maintenance
Maintenance contracts
Some sewage treatment systems come with maintenance contracts. These are generally reasonably priced - some are free for a period after sale.
Taking up a maintenance contract means your on-site sewage system will be properly maintained without you having to worry about it.
You may be able to check sludge levels yourself.
Inspections
Tanks should be inspected every six months or so.
If you have a maintenance contract, your contractor will do this for you. Otherwise, you’ll need an expert to do it. It is also a good idea to take a soil analysis from your soakage treatment area from time to time to test for contaminants. Look under Water Treatment, Water & Wastewater Services, or Septic Tanks in the Yellow Pages (www.yellowpages.co.nz).
Pumping
Older tanks generally need pumping every 3-5 years to remove sludge and sediment. The frequency depends on:
- what goes into the system
- how many people use it
- the capacity of the tanks
- whether you recycle greywater
- council requirements (some councils specify every two years).
However, if you have a good filter on a septic tank, you may be able to extend the pump-out period to 8-10 years.
If you have a maintenance contract, your contractor will do this for you. Otherwise, you’ll need an expert to do it. Look under Water Treatment, Water & Wastewater Services, or Septic Tanks in the Yellow Pages (www.yellowpages.co.nz).
Protect the soakage treatment area
Protect the soakage treatment area so that the effluent leaving the tank has optimum conditions to break down.
Don’t let people or vehicles on it, nor anything else that might disturb or compact the surface.
Trees cause problems when planted in soakage treatment areas as their roots can cause pipes to clog: grass and moisture loving plants are good choices instead.
Signs of trouble
Call for expert help if:
- you notice a disagreeable smell, either from your drains or from the soakage treatment area
- your toilets flush away slowly or your sinks and baths take a long time to empty
- your soakage treatment area is permanently wet - particularly where liquid seeps over the surface or if a green algae-like growth is forming (or you have excessive grass growth in dry weather).
If there’s a bad smell around your soakage area, it may be clogged with organic material. In this case, it may have to be moved.
If the smell is in your drains or toilet then sewage is backing up.
Some of these problems might indicate that your system doesn’t have enough capacity to deal with the wastewater you’re putting into it. If that’s the case, you’ll either need to put less waste into the system or increase its capacity and efficiency.
If you have a maintenance contract, call your contractor about any of these problems. Otherwise, look under Water Treatment, Water & Wastewater Services, or Septic Tanks in the Yellow Pages (www.yellowpages.co.nz).
More information
From Smarter Homes
- Choosing an on-site sewage system
- Waterless toilets
- Easy ways to save water
- Reducing water flow
- Reusing greywater
- Collecting and using rainwater
- Managing stormwater
- Outdoor water use
- Onsite sewage systems
From ConsumerBuild
Your local or regional council will have information about on-site sewage systems in your area. Consumerbuild’s Council finder web page has contact details for New Zealand local authorities.
From other sites
The Waitakere City Council’s website has a web page about on-site sewage systems.
The Greater Wellington Regional Council’s website has guidelines for onsite sewage treatment.
You can download The Story of Your Septic Tank (PDF, 1.2MB), a joint Ministry for the Environment/NZ Water and Wastes Association booklet, from the association's website.
You can buy copies New Zealand Standards relating to on-site sewage systems and waterless toilets from the Standards New Zealand website.
