You may notice a septic smell in your yard after it rains if groundwater is entering your septic tank and causing it to overflow. If you experience septic odors after rainfall, contact a licensed plumber. They can construct a drain to redirect rainwater away from your septic tank. 

Your septic tank naturally contains the good bacteria it needs, so you typically don't have to add more as the system produces them on its own. However, if you wish to replenish the bacteria, you can use natural methods. For example, you can add three rotten tomatoes to your garbage disposal or flush 1/4 ounce of active yeast down the toilet every three months. While store-bought septic enzymes and chemicals are available, many additives are unnecessary and may even harm your system. The most effective way to maintain a healthy bacterial balance is to avoid using chemical drain cleaners, which can kill the beneficial bacteria in your tank.

A two-way cleanout can help if there’s already a clog, but the best strategy to prevent one is by not rinsing grease, oil, or fat down your drains, not flushing or rinsing coffee grounds or egg shells down your drains, flushing only human waste and toilet paper (so no diapers, period products, bathroom wipes, or paper towels), and using drain guards on all of your drains.

Septic tanks appear full after pumping because the liquid levels have returned to normal. If you can see the pipe, the tank is empty. However, heavy rain can cause septic tanks to fill faster than normal. You might also have leaky pipes or faucets, causing extra water to drip down the drains and into the septic tank.