Deciding to build a granny flat is simple, designing and building the extension can be a lot harder. You'll have a lot of questions to answer along the way. Can you use a general contractor or is is better to use one who has built a lot of granny flats before? Is a template design better than a customised one? Should you let the person who'll live in the flat have a say in what it looks like? Luckily, I'm here to help. My name is Maria. We moved my Mum into a purpose-built granny flat last year, so I've had to answer all these questions and more. I thought it'd be useful for other people to see how we managed the process, so here we are — get reading!
How to Avoid Sewage Mixing with Storm Water
Most stormwater drainage systems are connected to the public sewer in some way. The challenge for construction firms who are responsible for installing a stormwater system under a new roadway or within a recently constructed housing development, for example, is to ensure that when significant rainfall occurs that the system does not overflow with sewage. How does the industry construct a connected stormwater system that still allows foul waste to continue its journey without negatively impacting the local environment?
Two Separate Run-Offs
Most urban sewage is disposed of in Australia via a public sewer network beneath the ground. To make this system work properly, waste water from washing up and baths also tends to flow into the same pipe. In fact, rainwater that flows into the system from culverts and drainage inlet points in the road will also help to keep all of the solid material in the sewer continuing its journey to the nearest processing plant as well. Trouble can occur, however, when you have some rain in a certain area that the drainage system overflow. To overcome this problem, two separate run-offs are designed into the system. This should mean that sewage continues to flow to the processing plant while excess water can be directed to another suitable location, such as a floodplain, a river or even the sea.
How Is Storm Water Separated from Foul Water?
When rainwater and sewage are both running together in an underground pipe, it is important to avoid the outcome of sewage ending up in rivers and lakes. Of course, in some places the storm drainage system is made entirely separately from the sewer so this is avoided. When a common pipe is used, however, there is an overflow system which is designed into the connections and allows for necessary separation.
Essentially, a common drain will be installed at a downward angle so that all the material flows in one direction. At some point where rainwater and sewage will be separated from one another, a pipe for sewage only will be fitted beneath the common drainpipe. Since solid material flows into this while water sits on top, excess water can be directed over a simple dam to an overflow pipe where it can be disposed of safely. The design means the sewage processing plant is not subjected to massive amounts of stormwater at the same time that the local environment is protected from raw sewage.
For more information, contact a stormwater drainage professional.