A long, grass-covered mound of soil that is several feet high near the home usually means there is a mound septic system. The mound is constructed of layers of sand and gravel with the perforated drainfield pipes running through it. A mound system is used when the ground is not suitable for a regular septic tank and drainfield, and there are a couple of possible reasons why:
1) The water table is high under the property, with not enough soil depth to absorb and filter the wastewater from the drainfield before it reaches the groundwater below and contaminates nearby wells. An example would be low land near a swamp.
2) The soil is too dense and resistant to allowing the wastewater to gradually move through it. Or the soil is too porous and allows the wastewater to move too quickly for good filtration. 

    The rate that water moves through the soil is called “percolation” and is determined by a “perc test” at the site. An alternative like the mound system has to be used when a home fails the perc test.

Should you buy a house with a mound septic system?

    A standard septic tank and drainfield operates entirely by gravity and is low-maintenace. But a mound system, on the other hand, requires a dosing chamber and pump to lift the wastewater up to the mound. Plus, a mound system will accept less abuse—like chemicals, grease, or excessive effluent flow—than a regular system. So there will likely be more maintenance, and the system will be more expensive to replace when the time comes. But, if you like the house and don’t find the mound offensive, it should be fine.

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And here’s some of our other articles about septic systems:

• What is the average life expectancy of a septic tank system?

• Should I buy a house with a septic tank?

 • What are the building code requirements for gray water reuse in Florida?

• What can I add to my septic tank to help it work better? 

• Why do septic tank contractors want you to get rid of your kitchen disposal?

• How can I tell if a house is connected to a septic tank system or sewer?

• How can I locate my septic tank?

• Does a septic tank have to be re-certified if a house has been vacant for a while?

• What is a grinder pump? 

• How often should I pump out the septic tank?

• Should I call a plumber or septic tank contractor when my septic tank backs up into the house? 

• Do I have to get a larger septic tank when I build a home addition?

• Where is the septic tank? Are you going to inspect it? 

• Can a house have more than one septic tank?

• What is the difference between gray water and black water in the plumbing code? 

• Is it alright to disconnect the washing machine drain from the septic tank and divert it to the ground in the yard?  

• Does a home inspector check the septic tank system?

• How do you abandon a septic tank?

• How close can you build a home addition to a septic tank system in Florida?

• Can you build a deck or patio over a septic tank in Florida?

• What is a septic loading dye test?

• What are the signs of a full septic tank? 

    Visit our SEPTIC TANK SYSTEMS page for more related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.

Mound system graphic - EPA