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.
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Field Guide for Home Inspectors, a quick reference for finding the age of 154 brands of HVAC systems, water heaters, and electrical panels, plus 210 code standards for site-built and manufactured homes, and the life expectancy rating of 195 home components. Available at amazon.com for $19.95.
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To learn more about SEPTIC TANK SYSTEMS, see these other blog posts:
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