Everything You Need To Know About Septic Tank Drain Fields

Jess Lynk
Written by Jess Lynk
Updated March 28, 2022
Friends having a garden party
Photo: Maskot / Maskot / Getty Images

A smelly septic got you down? Keep your yard fresh with the help of a drain field

Get quotes from up to 3 pros!
Enter a zip below and get matched to top-rated pros near you.

A drain field is a crucial part of a septic system that helps remove your home's waste. Needless to say, it'd stink if you didn't have one (sorry, we had to). Keeping unpleasant smells at bay is a prime reason to install a drain field, but it isn't the only one. They also manage runoff and help protect animals on your property. A drain field can last up to 50 years if you properly care for it. 

Here's everything you need to know about drain fields.

What Is a Drain Field?

A drain field is a part of a septic system. Its function is to remove waste from the tank and send it to pipes that slowly and evenly distribute the liquid into the soil. A little vocab lesson—drain fields are also known as leach fields and leach drains

Septic systems are underground onsite sewage facilities that treat residential wastewater. The system uses pipes and a tank to remove and treat the waste. The drain field then disperses the treated liquid into the soil. Septic systems are standard in rural areas, where sewer lines are hard to access. 

How Does a Drain Field Work?

A drain field works by using buried, sloped, and perforated pipes that connect to your septic and divert waste away from your home. The pipes deposit the waste into a porous material, like gravel or sand. This process helps prevent waste runoff and keeps critters from ingesting it.

Family playing soccer in their backyard
Photo: Kevin Dodge / Getty Images

Another vital function of a drain field? It helps ensure that your septic tank won’t overflow—because, let's face it, that wouldn't be pretty. A drain field also prevents pungent aromas from invading your yard (your nose will thank you).

Common Problems and Repairs

If your drain field is functioning properly, you shouldn't even know it’s there. If you notice issues like a foul odor, a wet or soggy area over your drainfield, slow to drain kitchen or bathroom drains or, worst of all, overflowing toilets and sewage backups, you likely have a drain field problem.

Even if you are particularly handy and knowledgeable, you likey need to call a professional to investigate what that problem is. Investigating septic tank drain field issues often involves specialized tools and equipment that most people don’t have on hand.  

The most common causes of drain field failure include:

Drain Field Age

While a properly maintained drain field is designed to last up to 50 years, it’s not likely that it will last much longer than that. If you’re experiencing symptoms of drain field failure and you know that your drain field is getting up there in age, it might be wise to begin to budget for a drain field replacement. 

Damaged or Blocked Piping

The pipes that carry wastewater to your drain field are designed to last but, like anything, they are susceptible to damage that can decrease their effectiveness. If heavy equipment (like cars) has been parked over the drain field or structures have been built over the piping, there is a chance that the pipes have been slowly compressed and crushed. Similarly, if the pipes have been blocked by either errant tree roots or things being flushed that should not have been flushed, they can become ineffective and lead to drain field failure. 

Septic System Overload

While septic systems should be able to handle a typical wastewater load, systems can become overloaded when more wastewater is being sent their way than is typical. For some septic tanks, that may be as simple as running the washing machine and dishwasher at the same time someone is using the shower.  

What Is the Maintenance and Cost of a Drain Field?

It's essential that you inspect and pump your septic system every two to five years to keep it in tip-top shape. Septic tank pumping costs an average of $290 to $530. If your drain field malfunctions, it could pollute your drinking water and cause damage to your yard. Installing or replacing a drain field can range from $2,000 for a small backyard to $20,000 for a large, high-end system. 

Who Can Install a Drain Field?

Installing a drain field is a big job that requires a permit, a crew, excavators, and possibly a crane if you need piping. Rather than tackling this project yourself, you can hire a septic company. The right contractor will install a drain field so you can enjoy the fresh air in your yard once again.

Need professional help with your project?
Get quotes from top-rated pros.