If you’re in your basement or near a floor drain and detect an odour that doesn’t smell like roses, you may be smelling sewer gas. Sewer gas, a by-product of decomposing waste, is a foul-smelling mix of gases. The toxic mix includes ammonia, methane and hydrogen sulphide that creates a rotten egg odour. Sewer gas is dangerous even in small amounts over long periods when it escapes into homes.

Plumbing codes are designed to keep it out with a simple device at every fixture that drains into a public sewer or private septic system: a P-trap. After you take a shower or wash dishes, the last cup or so of water down the drain stays in the bottom of the curved shape — trapped there, providing a seal between sewer gas on one side and household air on the other.

Symptoms and effects: Low levels of sewer gas, from sources such as a leaking wax seal under a toilet, can irritate eyes and throat and cause shortness of breath. Long-term symptoms include fatigue, headaches and dizziness – all things you might dismiss as a cold or the flu unless you smell the rotten eggs. The scent should be distinct until higher concentrations of hydrogen sulphide distort your sense of smell. Possible sources of sewer gas include:

• Plumbing fixtures whose traps have gone dry or have lost enough water that the seal within the trap has broken.

• Cracks in either plumbing drain lines or vent pipes are the other sources of sewer gas leaks. If the crack is in a drain line, there is often an associated visible water leak. But vent-pipe cracks are far more elusive and can go unnoticed.

• Sewer gas problems can also be caused by clogged pipes. This can happen in old homes where a cast-iron vent pipe gets clogged by years of rust scale that falls off the inside of the pipe.

Leaves and all sorts of other debris can clog plumbing vent pipes. When that happens, the replacement air needed by the system will get sucked into the pipes through a fixture inside the house. Once this happens, sewer gas immediately enters the room through the dry fixture trap.

If you suspect a sewer gas problem in your home, you should quickly contact a professional plumber to carry out the necessary tests. ClearView Services specializes in professional plumbing maintenance and installations. Our dedicated team is committed to resolving issues for our clients efficiently and cost-effectively, minimizing both expenses and disruptions.