Why does my house smell like sewer?

The most common cause is a dry trap. Every drain has a curved section of pipe that holds a little water to block sewer gas, and when a drain goes unused for a few weeks, that water evaporates and the smell comes right up. Run water in every sink, tub, and shower for a minute, pour a bucket of water into any floor drains, and see if it fades by the next day. If it doesn’t, check the toilets and the vent next.

Rotten eggs can mean gas. Gas companies add a rotten egg smell to natural gas so you’ll notice a leak, and sewer gas can smell a lot like it. If the smell is strongest near the stove, water heater, furnace, or gas meter, or you hear hissing, treat it as a gas leak. Get everyone out, don’t flip switches or start anything, and call the gas company or 911 once you’re outside. If you’re not sure which it is, assume gas.

Start with the drains nobody uses

Walk the house and notice where the smell is strongest. The usual spots are the guest bathroom, the shower nobody’s touched since the kids moved out, and floor drains in a laundry room, garage, or basement. Those traps sit untouched until they’re bone dry.

Run the faucet or shower for a minute. Pour a gallon or two into a floor drain. If the smell’s gone the next day, you found it. For a drain that sits unused for months at a time, pouring a little mineral oil on top of the water in the trap slows evaporation.

A trap can also dry out fast when the house sits empty for a while, like a vacation or a rental between tenants.

What if the smell is around the toilet?

Check the wax ring. That’s the seal between the bottom of the toilet and the drain pipe in the floor. When it fails, sewer gas escapes around the base, and sometimes water does too. Watch for a toilet that rocks when you sit on it, stains or soft spots in the floor around it, or a water stain on the ceiling below.

Swapping a wax ring is a fair DIY job if you’re handy and can lift a toilet. You pull the toilet, scrape off the old wax, set a new ring, and bolt it back down. If the floor under it feels soft, stop there and call us. That usually means water damage underneath, and a new wax ring won’t seal well on a bad floor.

Gurgling drains and a blocked vent

Your drain system has a vent pipe that runs up through the roof. It lets air into the pipes so water drains smoothly, and it carries sewer gas out above the house. When a bird’s nest or a wad of leaves blocks it, drains start to gurgle and slow down. Water rushing down one drain can also suck the water out of nearby traps, which puts you right back to the dry-trap smell.

Some sinks, especially kitchen islands and remodeled bathrooms, use an air admittance valve, a small one-way valve under the cabinet, instead of a pipe to the roof. They wear out, and when they do, the smell collects in that cabinet. If the odor lives under one sink, look for one.

Checking a roof vent means getting on the roof. If you’re not comfortable up there, leave it to us.

Other places a sewer smell comes from

• A cracked drain pipe. Houses from the 1950s and 60s, and Huntsville has a lot of them, often have cast iron drains, which can crack or rust through over time. If the crack is in a wall or the crawlspace, you’ll smell it long before you see it.
• A loose or cracked cleanout cap. Cleanouts are capped openings that give access to the drain line, and they’re often in the crawlspace, the garage, or the yard near the foundation. A bad cap lets gas out.
• The dishwasher or disposal. Food that sits and rots can smell a lot like sewage. Clean the dishwasher filter and run the disposal with plenty of cold water. If the dishwasher’s drain hose runs straight down with no high loop under the counter, dirty sink water can drain back into the dishwasher.
• The washing machine drain. The washer hose runs into a pipe called a standpipe, which should have its own trap. If the hose is shoved too far down or taped in tight, it can siphon that trap dry. Some older setups don’t have a proper trap at all.

What about homes on septic?

Everything above still applies on septic, but septic adds a few more possibilities. A full tank or a blocked line between the house and the tank can push odor back inside, and you’ll often smell it outside near the tank too. Most tanks need pumping every few years. If you can’t remember the last time yours was pumped, start there.

If you’re also seeing slow drains in more than one spot, read up on the signs of a clogged main sewer line. Most of it applies to septic lines as well.

Sulfur smell only from the hot water?

Run the cold water at a sink and smell it, then run the hot. If only the hot water stinks, look at the water heater. The anode rod inside the tank can react with bacteria in the water and produce that rotten egg smell. Your drains aren’t involved. Swapping the anode rod for a different type usually takes care of it.

If you’ve run every drain, checked the toilets, and still smell it a week later, call us.