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Why we have such complicated septic tank disposal rules

By Anna Bensemann | Nov 12, 2020

There is a frustrating moment when building or extending your house becomes held up by Council for building consent because they want to know if your septic tank system meets the current day standards. Frustration continues when it becomes apparent that your current system is not sufficient to meet the standards, simply because you are adding another bedroom or a media room that the council is now calling a bedroom. The boiling point really sets in when you realise the costs of upgrading your system to meet the necessary standards.

When extending a dwelling in the rural environment and you don’t have access to council sewer, it’s important to be aware of the potential issues you are uncovering. Many septic systems were installed during a time when resource consents to discharge to land were not required, and often these systems have never been managed since, except to perhaps get the tank emptied when it gets a bit stinky.

However, wastewater systems include a tank system of some type, and a discharge disposal field where the liquid overflow from the tank drains. New Zealand standards require the system, including the discharge area, meets the most current standards, and these standards calculate how big your system needs to be based on the number of bedrooms or potential bedrooms a dwelling has.

Hang on a minute – just because you are increasing the number of bedrooms doesn’t necessarily mean that you will have more people using the system, right? This may be correct, but council are required to look at the overall potential use of the property, so if you sold tomorrow and a new person used the system, how many people could possibly live there?

While this maximum occupancy approach seems a little unfair for you, this is a public health matter because if the system fails and effluent ends up in drinking water, we have a recipe for disaster. At worst it could mean death for vulnerable young or old, and at best it would mean you could feel very ill and not know why.

So when you are extending your dwelling to add more room for when the kids come home or grandkids come to visit, be aware that you will be required to consider your septic tank system and determine if it is sufficiently sized, or that you may need to upgrade it. This carries a cost component that you will have to budget for. For the sake of ensuring quality drinking water supply, this really is a small price to pay.