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Most homeowners with septic systems rarely take a moment to think about their leach fields. However, this essential part of your system works hard day and night to distribute treated wastewater beneath your yard.

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Unfortunately, leach fields can go wrong, with potentially unpleasant results. Therefore, it's worth factoring the costs of leach field repair and replacement into your home maintenance budget.

What Is a Leach Field or Drain Field?

Leach fields, also known as drain fields, are part of your septic tank system. They comprise a network of underground pipes with tiny perforations that allow liquid to escape into the soil. Leach fields are usually buried under a flat area in your backyard.

You need to understand how your septic system works to appreciate the importance of your leach field. When you flush the toilet or run water down the sink, solid waste and wastewater travel down the drain to the septic tank. Your septic tank contains bacteria that break down the solid waste, causing it to sink to the bottom and form sludge. These bacteria also tackle liquid waste, such as oil and scum. The remaining liquid then passes through the perforated pipes in the leach field.

How Do You Know You Need to Repair or Replace Your Leach Field?

You won't even notice your leach field is there if it functions correctly. Leach fields shouldn't make any sound or release unpleasant odors. One of the first signs of a malfunctioning leach field is a sewage smell in your yard or around the drains or septic tank. You may also notice gurgling noises coming from your pipes or plumbing fixtures.

Another telltale sign of a faulty leach field is the accumulation of standing water in your yard or on the ground that feels wet or mushy without significant rainfall. It can also cause slow drainage, backed-up drains and toilet flushing problems inside your home.

Your leach field is more likely to develop a fault if your family uses a lot of water, for example, by doing multiple laundry loads each day. Flushing solid items down the sink or toilet can also contribute to leach field issues, and parking cars or placing heavy items over the leach field can cause damage. Clearing a blocked leach field is relatively straightforward, although you may need to replace it if there is significant damage.

How Long Does a Leach Field Last?

You can expect your leach field to last between 20 and 25 years with proper maintenance. However, its lifespan could be significantly shorter if it wasn't installed correctly or you don't have your septic system cleaned regularly. Generally, you should pump and clean your system every 3 to 5 years to keep it in good working condition.

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How Much Does Leach Field Replacement Cost?

According to data from HomeGuide, on average, leach field replacement costs around $7,900 (CAD 10,556)), with most homeowners paying between $3,000 and $15,000 (CAD 4,009 and CAD 20,043). However, the type of leach field can affect how much it costs to replace:

• Anaerobic leach field: $2,000 to $6,000 (CAD 2,672 to CAD 8,017)
• Aerobic leach field: $7,000 to $10,000 (CAD 9,353 to CAD 13,362)
• Evapotranspiration leach field: $8,000 to $15,000 (CAD 10,689 to CAD 20,043)
• Mound leach field: $10,000 to $20,000 (CAD 13,362 to CAD 26,724)

Replacing your septic tank as well can significantly increase the cost of leach field replacement. You should expect to pay between $4,500 and $20,000 (CAD 6,013 and CAD 26,724) to install a new septic tank and leach field. If you'll need to remove trees before the job can be done, it may also add $300 to $2,000 per tree (CAD 401 to CAD 2,672), depending on the size.

How Much Do Leach Field Repairs Cost?

Most homeowners spend between $1,000 and $5,000 (CAD 1,336 and CAD 6,681) on drain field repairs, based on HomeGuide's data. How much you'll spend depends on the type and extent of the issue. Replacing individual leach lines usually costs between $20 and $45 (CAD 27 and CAD 60) per linear foot. These figures include:

• Excavation
• Removing old pipes
• Installing new pipes
• Installing new septic chambers
• Refilling the area around the leach pipes

If you have leach field problems, but the pipes are otherwise in good condition, leach field rejuvenation could be an alternative to replacement. This process involves forcing air into the soil around the leach field to improve oxygen levels and increase the number of bacteria in the lines. Expect to pay between $1,000 and $5,000 (CAD 1,336 and CAD 6,681) for leach field rejuvenation.

Alternatively, you could consider installing a septic aerator to revitalize a leach field that isn't working correctly. Septic aerators increase oxygen levels inside the septic tank to help it break down waste more effectively, reducing pressure on your drain field. Installing a septic aerator usually costs between $300 and $900 (CAD 401 and CAD 1,203), including labor and the cost of the unit.

All CAD conversions are based on the exchange rate on the date of publication.