How much does it cost to replace a septic tank?

Replacing only the septic tank typically costs $3,500 to $8,500 for a three- or four-bedroom home, as long as the drain field is still working. Replacing the tank and the drain field together usually costs $4,500 to $20,000, and Angi reports an average of about $6,000. If your site now needs an engineered system, such as a mound or aerobic unit, the price can climb past $20,000.

The first question is what actually failed. A cracked tank, a broken baffle and a flooded drain field are three very different bills.

Septic replacement cost at a glance

Job	Typical cost	When it applies
Repair a tank part (baffle, lid, crack, filter)	$150 – $900	The tank is sound but one part failed
Replace the tank only	$3,500 – $8,500	Tank is cracked, rusted or collapsing; drain field works
Replace the drain field only	$3,000 – $15,000	Tank is fine; field is saturated or clogged
Replace tank and drain field	$4,500 – $20,000	Whole system is at the end of its life
Full replacement with engineered system	$15,000 – $50,000	Soil or code no longer allows a conventional system
Abandon old tank in place	$500 – $1,000	Old tank is left buried and filled

Sources: HomeGuide, Bob Vila (Angi data) and HomeAdvisor.

Tank-only replacement

A tank-only job includes pumping the old tank, digging it out or abandoning it, setting a new tank, and reconnecting the inlet line from the house and the outlet line to the drain field. HomeGuide puts this at $3,500 to $8,500. The final price depends on tank size, material and how much gravel or fill is needed to bed the new tank.

The new tank itself is the smaller part of the cost:

Tank material	Tank price before installation
Concrete	$700 – $3,000
Plastic (polyethylene)	$500 – $2,500
Fiberglass	$1,200 – $2,000

Your replacement must meet today’s code, not the code your house was built under. If you have added bedrooms, or your county raised its minimum tank size, the new tank may need to be bigger than the old one.

Full system replacement: tank and drain field

When the drain field has failed too, you are effectively buying a new system. HomeGuide puts a new tank and leach field at $4,500 to $20,000. Bob Vila, citing Angi, reports an average of $6,000 with a range of $2,000 to $20,000.

Prices by system type, based on Angi data reported by Bob Vila:

Replacement system	Average cost with installation
Anaerobic (conventional) system	$5,000
Aerobic system	$7,000
Mound drain field system	$12,000

Real-world local numbers can be higher. The Jefferson County Conservation District in Washington says the average full replacement there now runs $16,000 to $20,000, including permit fees, a soils evaluation, an engineering design and the work itself. Washington’s Department of Ecology says a new system in the state can cost $30,000 or more.

A full replacement also brings back the same up-front costs as a new install: a perc or soil test ($600 to $2,000), permits ($250 to $2,000) and design work. Our septic tank installation cost guide breaks those down by system type. For the drain field alone, see drain field replacement cost.

What happens to the old septic tank?

You have two options, and your local health department decides which is allowed.

Abandon it in place

This is the most common approach. The tank is pumped, the lid is removed or the tank is broken so it cannot hold water, and the cavity is filled with sand, gravel or other approved material. HomeAdvisor puts abandoning a tank at about $500 to $1,000. HomeGuide lists abandonment permits at $100 to $250.

An empty or poorly filled septic tank can cave in under a person, pet or mower. Never leave an old tank open or empty, and never climb into or lean into a septic tank. The gases inside can be deadly.

Dig it out and haul it away

Full removal costs much more because of the excavation, hauling and disposal. Bob Vila estimates the added cost to remove and dump a septic tank at about $5,500. Removal makes sense when the new tank must go in the same spot or the space is needed for a building.

Repair or replace?

Many problems that look like a failed tank are really one broken part. Before you agree to a replacement, ask whether a repair would solve it.

Repair	Typical cost
Septic tank filter replacement	$200 – $300
Lid replacement	$150 – $600
Baffle repair	$250 – $900
Cracked tank repair (small cracks)	$500 – $850
Effluent pump replacement	$500 – $1,300
Distribution box replacement	$500 – $1,500
Drain field rejuvenation	$1,000 – $5,000

Source: HomeGuide.

A baffle is the wall or pipe fitting at the tank’s inlet and outlet that keeps floating scum and settled sludge from leaving the tank. A distribution box splits effluent evenly among the drain field lines. Large cracks, a collapsing tank, or a rusted-through steel tank usually mean replacement.

Signs you need a new septic tank or system

• Sewage backing up into drains or toilets, especially after pumping
• Sewage odors in the yard or house
• Standing water or soggy ground over the tank or drain field
• Slow drains and gurgling toilets throughout the house
• A sunken area in the yard over the tank
• Unusually green, lush grass over the drain field
• A steel tank, or a concrete tank that is several decades old

Concrete tanks commonly last 20 to 30 years, and This Old House notes they can last 40 or more with good care. Steel tanks often need replacement after 15 to 20 years.

Sewage backups, alarms and soggy drain fields call for a licensed septic professional, not a DIY fix. A septic inspection is the cheapest way to learn whether you need a repair, a new tank or a whole new system.

Replace the system or connect to sewer?

If a public sewer line runs near your property, connecting may be an option. Fixr puts a sewer connection at about $1,500 to $8,000, compared with $3,100 to $9,600 for a typical septic system. The connection price depends heavily on how far the house is from the main, and sewer service brings a monthly bill that septic does not. You will still need to abandon the old tank properly. Ask your local health or public works department whether sewer is available and whether a connection is required.

What a replacement involves, step by step

1. Inspection and diagnosis to confirm which parts failed.
2. Soil evaluation and design if the drain field is being replaced, since the new field must meet current code.
3. Permits for the new system and for abandoning the old tank or field.
4. Pumping the old tank so it can be abandoned or removed safely.
5. Removal or abandonment of the old tank.
6. Installing the new tank and, if needed, the new drain field.
7. Inspection by the county before backfill, then grading and seeding.

How to keep replacement costs down

• Diagnose first. Pay for an inspection, and a camera inspection if needed, before you accept a replacement quote.
• Get three or more written quotes and check that each includes pumping, abandonment, permits and lawn repair.
• Ask about keeping the drain field. If it passes inspection, a tank-only job can save thousands.
• Check for help. Washington offers income-based loans and grants through Craft3. Massachusetts offers a tax credit of 60% of eligible costs, up to $4,000 per year and $18,000 total, when Title 5 requires a repair or replacement.

When you are ready to compare prices, you can request quotes from local septic pros.