How long can a septic system sit unused?

Author: Ms. Stefanie Sporer IV  |  Last update: Saturday, September 13, 2025

Will my septic system be ruined if I don't use it for an extended period of time? A standard septic system that was working properly and then not used for a period of time, such as 4 – 5 years, typically does not lose effectiveness or the ability to function properly once it is put back into use.

How long can a septic system sit unused in the ground?

Under the right conditions, a well-designed and built septic system can sit for years with no problem.

How do I reactivate a septic system?

If Tank has not been pumped for 2+ years Mix 2lbs of Bio-Clean (1 can) with 20L of warm water and apply directly to the solids side of the septic tank for 3 consecutive nights (3 cans total). If the tank is not accessible, flush down toilet closest to the tank.

Can a septic tank go 20 years without being pumped?

A normal working system only needs to be pumped when the sludge level is a third or more. A good well designed working septic system can easily go 20+ years and not need pumped.

Is it OK to leave an old septic tank in the ground?

There are regulations in place today for abandoning a septic tank properly, but years ago, it was common to just leave the tanks in place and forget about them. An old septic tank on your property is a huge safety risk, especially if you have kids, pets, or livestock.

Understanding Septic Systems | Ask This Old House

How much does it cost to abandon a septic system?

The Town recommends that you obtain multiple estimates from qualified contractors. Each situation will be different, but you can plan on the cost to properly abandon a septic system to range between $1,000 - $2,000.

Can you build over an abandoned leach field?

Not only could building over a leach field cause damage to the structure, it could also slow down the dispersing of the wastewater itself. That's because oxygen is needed for evapotranspiration. The oxygen allows the microbes in the soil to continue to treat the wastewater as it flows out of the pipes.

What happens if you never drain your septic tank?

This can lead to sewage backups, which are not only unpleasant but also pose a significant health hazard. In addition to sewage backups, neglecting septic tank pumping can result in untreated sewage being released into the environment, polluting nearby soil, groundwater, and even surface water sources.

How long does it take for poop to decompose in a septic tank?

On average, it takes anywhere from three to five years for waste to fully decompose in a septic tank. The decomposition time for waste in a septic tank can vary based on several factors, including the tank's size, the number of occupants in the household, and the types of waste introduced.

How much does it cost to have a septic cleaned out?

The average cost to pump a septic tank is $423, with most people paying between $289 and $557. Septic tank pumping isn't the most glamorous task, but it's one that you should definitely stay on top of every three to five years to keep your system working properly and avoid an unsightly (and smelly) mess in your yard.

How often should I put baking soda in my septic tank?

Use Baking Soda

By flushing 1/2 cup of baking soda down the toilet weekly, you can help to maintain the pH balance in the tank and encourage beneficial bacteria to break down waste.

Does homeowners insurance cover septic back up?

Home insurance may pay to repair septic tanks and pipes that are damaged by fire, lightning and other covered events. It doesn't cover damage caused by lack of maintenance, wear and tear, tree roots or improper installation. Homeowners with septic tanks should consider buying additional water backup coverage.

How many years can a septic system last?

The average lifespan of a septic system is 15 to 40 years, but it can last longer if properly maintained! Think at the sink. Consider what you put into your toilet and sink and the impact it may have on your system. Many common household items can either clog your system or kill the microbes that treat the wastewater.

What happens to an unused septic tank?

An improperly abandoned septic system poses several possible risks. They could collapse into sinkholes, spread disease if untreated waste comes into contact with groundwater, or release toxic gasses like methane and hydrogen sulfide.

How do I reactivate the bacteria in my septic tank?

You can replenish good bacteria in your septic tank by adding three rotten tomatoes or 1/4 ounce of yeast every three months. Put three overripe tomatoes in the garbage disposal while running the faucet. Or pour 1/4 ounce of yeast in the toilet and flush it down.

Can you live in a house with a failed septic system?

If defective, the house cannot be occupied without a functioning septic system. Either the seller needs to repair/replace, or the buyer does. If the seller doesn't fix it, a discount is usually given to the buyer for the cost of repair/replacement.

Can a septic tank go 30 years without being pumped?

In general, a septic tank should be inspected every 1 to 3 years and pumped every 3 to 5 years. The frequency of pumping the septic tank depends on the tank size, number of people in the household, habits of water use as well as the amount of solids accumulated in the tank.

What is the best thing to put in your septic tank to keep it clean?

Use a Septic System Additive

Waste & Grease Eco-Friendly Digestant makes it easy to maintain a clean and sanitized home environment as well as a healthy bacteria population in your septic tank. Monthly use of Waste & Grease Eco-Friendly Digestant will help reduce surface and bottom solids in the septic tank.

Does bacteria eat poop in septic tank?

These bacteria feed on feces and any other carbon-based organic molecules like toilet paper and food particles. As the bacteria feed, all of the solids get broken down into a thick sludge that settles at the bottom of the septic tank.

What happens if you wait too long to pump your septic tank?

And if you don't have that information, it's a good idea to go ahead and get the system pumped just to be safe. If you wait too long between pumping your system, you could be at risk for sludge buildup and eventually damage your drainage system.

Can a leach field last 100 years?

A well-designed leach field will last between 15 and 50 years. The dramatic lifespan difference is based on several factors, including: Maintenance – Regular inspections and pumping every 5-10 years can extend the field's functional life.

What are the signs that your septic tank needs to be emptied?

6 Signs Your Septic Tank Is Full
  • Strong Odors. The first sign you will notice when it is time to call a professional is a foul odor. ...
  • Gurgling in the Plumbing. If you don't smell anything, you may hear something. ...
  • Toilets Flush Slowly. ...
  • Pooling Waters. ...
  • Faster Growing Grass. ...
  • Backup.

Does homeowners insurance cover leach field?

Your homeowners insurance should cover septic system damage as long as your policy includes coverage for other structures. Other structures often include the fence that surrounds your backyard and your swimming pool. You can file a claim if you can prove that the problem did not occur due to neglect on your part.

Can you sell a house without a leach field?

Contrary to some other answers you have gotten, you can sell any house, in any condition including a failed septic system. It is just a question of the price you can expect someone to pay. Provided you disclose the problem before the sale, you cannot be held liable for the failed system after the sale.

Can you put a gravel driveway over a septic drain field?

You should never install the following over a drainfield:

Driveways.

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