The primary function of your drain and sewage plumbing is to take things away from your house, like water and other waste. It’s not supposed to bring anything to your home, which is why if you detect smells coming from your drains, or even your water, you have a big problem.
Fortunately, you don’t have to panic. Having bad smells in your plumbing is an issue, and pretending it’s not happening may put your home at health risk, but you’d be surprised at how many solutions for these problems aren’t that difficult.
Fixing a Smelly Drain
If a single drain has a bad smell coming out, this might just be a simple case of an empty p-trap. Your p-trap is the bend in the pipe under your sink.
It is designed to hold a certain quantity of water that acts as an incredibly efficient vapor barrier that keeps 
away sewer gas which naturally floats about through a pipe.
Sometimes, this p-trap can dry out, or can empty out if water coursing through your plumbing in another part of the house creates enough difference in air pressure to cause water movement elsewhere, sucking a p-trap dry.
You can easily solve this by simply getting more water and pouring it down the drain.
This is a very common cause, so be sure to try this first if the smell is only coming from one source.
Fixing Smelly Water
If your issue comes from turning on the tap or shower and smelly water is coming out, then your problem lies deeper in your home. In your water heater tank, in all likelihood.
If the temperature in a water heater tank is “just right,” bacteria can take advantage of that warm, moist, dark environment to infest the area.
The solution to this is to make your water heater tank no longer “just right” for bacteria. All it takes is increasing the temperature to something in the neighborhood of 135-140°F.
That level of heat is lethal to the vast majority of bacteria, especially those which can pose a health threat to people.
Fixing a Sewage Line
There are a range of problems that can affect smells coming from the sewage system of your home itself.
If your problem is one of ventilation, this might be a quick fix.
Just check the vents for obstructions like leaves, and clear it out to get rid of the problem.
If the issue runs deeper into your sewage line itself, this is probably beyond the scope of a simple DIY fix and will require experienced professionals with serious hardware and technology to fix the issue.
For example, if tree roots have breached your home’s old sewage line, that’s slowly causing a block, you’ll need a professional to help with this.
