How To Look At A House

McGarry and Madsen's home inspection blog for buyers of  

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What is safe to plant over a septic drainfield to avoid problems?

Friday, July 8, 2022

Planting grass or ground cover plants over the septic tank drainfield is critical for keeping the soil intact, and also helps absorb and evaporate the effluent water flowing from the drainfield. But it’s equally important that whatever you plant has a shallow, non-aggressive root system to avoid roots clogging drainfield laterals or, even worse, getting into the tank itself.

    Grass is always a good choice. Saint Augustine, Zoysia, and Bahia varieties work well. Pampas grass, bamboo, and other large grasses should be avoided because of their deeper root systems. 

    Landscape ground covers like perennial peanuts—with their tiny, bright yellow flowers—are another good choice. Other herbaceous shrubs (ones without woody branches) with shallow root systems are also recommended. The University of Florida’s IFAS agricultural extenstion recommends cast iron plant, milkweed, aster, bluestem grass, plumbago, or pink Muhly grass.

    Trees located anywhere within 20-feet of the drainfield are a definite no-no. And large trees with aggressive roots systems should be kept even further away, since their roots can extend out up to three-times the radius of the canopy.

    There’s several other considerations too:

•• Keep sprinklers away from the drainfield area. If you are unsure of the outline of your drainfield, your local office of the Florida Health Department will have the location and dimensions of the drainfield on file, since a plan was part of the permitting process.

•• The minimum depth of the top of a drainfield pipe is 6-inches, so avoid digging more deep than that with a shovel in the drainfield area. Even though the lateral pipes are typically 6-feet or more apart, you might be unlucky and damage one.

•• Don’t add mulch, gravel, or landscape cloth over any of the drainfield area.

•• Rain gutters should not drain to the drainfield, and the drainfield surface should slope to drain away rainwater.

•• Never drive across the drainfield area. This can damage the drainfield pipes and compact the soil. 

•• The average time between pump-outs is about 5 years, and it varies depending on the number of occupants in the home. But, if you wait too long for a pumpout and the backed-up sludge flows out into the drainfield, the damage may be unrepairable. 

•• Don’t plant a vegetable garden over the drainfield. Although the effluent does provide soil nutrients, it could also contaminate the vegetables with dangerous pollutants or bacteria.

• • • • • • • • • • • • • • • • • • • • • • • • • • •  

  To learn more about SEPTIC TANK SYSTEMS, see these other blog posts:

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

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

Should I buy a house with a septic tank? 

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 the maximum soil cover over septic drainfield lateral lines in Florida?

What is a grinder pump? 

How often should I pump out the septic tank?

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?

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

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?

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

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