Understanding Stormwater and Sewer Drainage

In recent years many of us have become a lot more aware of what we’re putting down our drains and how we’re using/recycling our water. We’ve been told about the need to keep wet wipes and microfibre particles out of our water system. And we’ve been introduced to easier and more efficient ways to collect rainwater to use.

So let’s take a closer look at our sewage and stormwater systems.

There are two broad categories of water that drains away from your home (as opposed to the fresh water that gets plumbed into your home for you to use).

What is sewage?

Sewage is the wastewater that is generated by you and your household members in your home. It includes water from your sinks, bath, showers, washing machine, dishwasher and toilet.

From this list you can see that the water from these sources would likely include soaps, detergents, toxins, household waste and elements of human waste. It is not water that you could safely reuse without treating it.

This water runs from your drains and pipes into the sewage system to a treatment plant. It runs through your underground piping, which is why you notice a foul smell if there are any leaks or damage in your sewage pipes. A common cause of leaks or damage to underground pipes is the intrusion of tree roots, which the Sumich team can treat with root cutting.

What is stormwater?

Stormwater is water that drains off your roof and property after it rains. The spouting, gutters and downpipes on your home collect and channel rainwater (and melting snow in some parts of the country) so that this water runs off your roof in a way that doesn’t cause damage to the external or internal walls of your house.

You may also have other stormwater drains around your property that collect and channel rainwater to drains so it doesn’t just pool in one spot. If you have a water tank or rainwater tank, stormwater is the water that is collected.

Stormwater may have some dirt and debris, and possibly even contaminants from birds or animals on your roof or in your gutters. However, this water generally doesn’t have as many toxins or chemicals as wastewater does because stormwater hasn’t been used for washing, personal care, etc.

Other terms to describe sewage and stormwater

You may have heard the terms potable and non-potable in reference to water. Potable water is water that is safe for consumption. It is safe to drink, cook with, brush your teeth with, etc. Basically, if you drank it, you would not get sick. Non-potable water, on the other hand, is unsafe for human consumption and could make you very sick.

Other words you may hear used in reference to wastewater are grey water and black water. This, too, refers to how safe or unsafe water is for consumption. Grey water usually refers to water that has been used, from sinks, showers, baths, washing, etc.

Black water usually refers to water from bathrooms that contains human excrement or other disease-carrying bacteria. There is debate over whether water from kitchen is considered grey or black, as it may be contaminated by pathogens or grease.

Why is it important to know the difference between sewage and stormwater drainage?

All of the plumbing and drainage systems in and around your home function together to keep you safe and dry. Because it can be a complex system of drains and pipes, it’s important to keep everything maintained properly to avoid costly repair and, most importantly, to keep you and your family safe from harmful bacteria and pathogens that can make you very sick.

Sewage work we can help with includes:

  • checking all of your internal pipes and drains, around your sinks, showers, bath
  • checking that appliances like your dishwasher and washing machine are all draining properly
  • checking that your toilets are flushing properly and running efficiently
  • inspecting your underground pipes
  • making sure there are no roots interfering with your drainage

Stormwater drainage work we can help with includes:

We don’t recommend doing any of this work yourself. There are harmful bacteria in wastewater and sewage that can make you and your family very sick.

It’s best to call in the team at Sumich Plumbing & Drainage for a free quote* excluding roofing on all your plumbing and drainage needs.


There are a number of plumbing and drainage companies in Auckland, so why choose Sumich?

Founded by owner-operator Chris Sumich in 1991, Sumich Plumbing & Drainage has one of the most experienced teams operating in Auckland. Our team has a combined experience of over 100 years and we’ve seen a comprehensive range of scenarios and solutions over the years. Clients trust us to give honest, transparent advice and service.

As registered members of the New Zealand Plumbers, Drainlayers & Gasfitters Association, we are professional, licensed Auckland plumbers for all of your plumbing, drain laying, gas fitting and heating needs. Give us a call to see how we can help.