Frequently Asked Questions

Sand, bark, wood chips, gravel, or plain dirt over your drainfield may sound easy, but these materials keep oxygen from getting into the ground, and bare soil can start to wash away. Plants help with oxygen exchange, keep soil healthy, and hold dirt in place so your drainfield can do its job.

Risers: If you don't already have risers, installing them is a great idea. They allow for easy access to tanks during routine inspections and pumping. Protect septic lids when mowing, but do not cover with heavy or permanent objects.

Plants & Ground Covers: Things like bark, wood chips, and gravel are okay here. Wastewater is not treated in the soil next to tanks, so there isn't a need for plants. All the other advice still applies though. Don't put anything heavy over this area. If you do plant something, stick to shallow-rooted plants to avoid damage to tanks and pipes.

Some septic systems have lids out in the drainfield. These are access ports that allow for easy inspection of the drainfield. Make sure that your landscaping doesn't bury or hide them, and protect them when mowing.

Protect this the same way as your drainfield. If you do things to damage the soil in your reserve area, it may not be useable in the future for a replacement drainfield if your current one fails.

IMPORTANT: Some drainfields are buried a few feet underground, while others are as shallow as 6 inches. If you have a shallow drainfield, not all of the plants listed below may be suitable. Try to find how deep your drain lines were installed by checking your septic records. Always consult with a nursery professional before choosing plants other than grass to make sure it has shallow enough roots to avoid damage.

Grasses for Sun

• Turf grasses
• Fescue

Ground Covers for Sun

• Bugleweed
• Carpet heathers
• Kinnikinnick
• Cotoneaster
• Thyme
• Stonecrop
• Soapwart

Plants for Shade

• Bishop's hat
• Bunchberry
• Shallow-rooted ferns
• Mosses
• Salal
• Sweet woodruff
• Wild ginger
• Wintergreen
• Japanese spurge

Wildflower meadows: This is a common suggestion for drainfields but if you do this, make sure your wildflower mix...

• Is a Washington/Northwest mix
• Specifies no noxious weeds
• Has both annual and perennial seeds
• Does not have plants that require extra water or have long roots