Why Does My Yard Smell Like Sewage After Rain? (Explained)

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There are a couple of reasons rain leaves a sewage-like smell in your yard, and you need to carry out tests to find the specific reason. Common reasons, however, include a broken pipe, a full septic tank, or insufficient bacteria to digest your waste.

Heavy Rains In Backyard

Why Does My Septic Tank Smell After Rain?

An offensive odor in or around the house after every rain is certainly a sign of a much bigger problem. When you notice a stench, presumably from your septic tank, try to find out why it always occurs after rain; as you’re doing now.

A smell from your septic tank after a rain usually signifies a problem, either with your septic tank or with your general home plumbing. If your plumbing system is unable to get rid of dirty water, you’ll always have a foul smell hanging around after every rain.

However, that isn’t the only possible cause of a septic tank smell. There might be many other explanations for the offensive odor, and the one that may apply to you depends on where you can perceive the smell.

If it’s in the yard outside the home, a weak odor may not be a sign of a malfunction. Since the septic tank works to dispose of sewage, it’s only normal to perceive a weak smell from around the tank.

However, if the odor is so strong that it’s almost unbearable, it’s a problem sign. In this case, you should watch out for broken pipes. A broken pipe can allow rainwater to flow into the septic tank, forcefully expelling the sewer gas that smells terribly.

When the rainwater takes the place of this sewer gas, the gas comes to the surface with an offensive smell that’s akin to that of rotten eggs.

Also, the septic tank cover might not be sealed properly. Opening the cover to your septic tank can be quite hazardous, and it isn’t recommended unless you’re a professional. If you’re like most people, however, you’ll be unwilling to open it, even if it’s recommended.

If the septic tank smell is exceptionally strong inside the home, the culprit may be a full tank. When your septic tank gets filled, it naturally emits an unhealthy odor that compels you to pump it out.

A full septic tank isn’t a common occurrence by any means. If you use the tank properly with the water usage of a typical home, it should last for about four years before needing a pump.

If you’ve pumped out your septic tank recently, the problem is almost certainly not a blocked or full tank. In this case, the pump may be the cause of the smell, which will naturally fade away as time goes by.

A newly pumped out septic system also loses most of the bacteria that digest the waste to convert them into liquids and gases that are easier to percolate. This slows the process of getting rid of the waste, leaving the stench as a sign.

Another reason why your septic system may not have enough bacteria to digest your waste is that you flush too many strong cleaners into the tank. These kill the bacteria, leaving your waste unattended to, and you, with a foul smell.

In short, when next your septic tank smells like sewage after a rain, you should know that it’s either because the tank is full, a pipe is leaking, or useful bacteria are dying. And in cases where the smell is very mild, it may be perfectly normal.

How Do I Find the Sewer Smell in my Yard?

If you suspect that the offensive odor in or outside of your building is caused by sewer gas, it’s best to find a professional to help you detect the origin of the smell. Doing it yourself can be time-consuming, and there is no guarantee that you’ll be successful, given your lack of experience.

The whole process of finding the source of a sewer smell takes a few hours at most when done by a professional. You should also expect to pay anything between $500 and $2,500, depending on the size of your house and sewage system.

If you’d rather find the sewer smell on your own, there are a lot of methods to try. If any of the following methods don’t seem to work, you should be looking to hire a professional.

Flush your pipes

Since the smelly gas is usually from leaking pipes, you can easily find the exact spot of the leak by flushing all the pipes around your home’s plumbing.

Flushing your pipes with boiling water can help you detect where the smell is coming from and if it’s a leak. If it isn’t a leak, the water can remove the biofilm that could be causing the smell.

Conduct a smoke test

The smoke test is best done by a professional plumber, as it’s a very tasking and time-consuming exercise. In addition to the difficulties attached to this test, the success level is low, especially for inexperienced plumbers.

The smoke test involves blowing smoke into the area of interest. When the whole area is filled, the plumber can identify the area where the sewer smell comes from due to the smoke that evolves from there.

If you try this test yourself without success, you can hire plumbers to carry it out on your behalf. The costs for a smoke test can range from about $500 to about $5,000, depending on the size of your home and the severity of the problem.

How Do You Get Rid of Sewer Smell Outside?

If your house has a sewage-like smell in the yard after every rain, you should take proactive measures to correct the smell before it escalates to a bigger problem.

There are many ways to get rid of sewer smells in and outside of the house, and the one you’ll adopt depends on the cause of the problem. If you hire a plumber, they can easily tell the most appropriate solution to the problem, while you may need to go the trial and error route.

Here are some ways to get rid of a sewer smell that gets much worse after rains.

Raising the mouth of a brick well. Installing a septic tank for a house

Pump out the septic tank

If you use a septic system to get rid of your waste, the incessant smell could be because your tank is either full or blocked. In this case, you may need to pump out the septic tank to quell the smell.

It’s important to note that the smell may persist for a few days after the pump, but it will gradually reduce, and finally stop completely.

Pumping out the septic tank is a task for professionals and you shouldn’t even attempt to take off the seal to the tank unless you’re a professional yourself.

Use bacteria additives

Sometimes, the sewer-like smell from your septic system may be due to the inability of the available bacteria to properly discharge waste.

If you suspect this to be the case, you can use bacteria additives that create the optimal conditions for bacterial growth in the septic system. This restores the volume of bacteria required to discharge waste from the septic tank, effectively ridding the home of offensive sewage smells.