Septic System: FAQ’s
April 30, 2013
Septic System: FAQ’s
April 30, 2013
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General Questions

How long do septic systems last?
Septic systems are designed to provide long-term, effective treatment of household waste when operated and maintained properly. However, most systems that fail prematurely are due to improper maintenance. Less serious problems are usually with plumbing (such as pipe blockages from tree roots growing into the pipe). Sometimes, the septic tank, although durable, can deteriorate or have other structural problems. The most serious problems are the result of a clogged drainfield. Unfortunately, this is the most expensive to repair. Once the absorption field is clogged, it must be replaced and can cost thousands of dollars.

What is the replacement or reserve area?
This is an area that may be used for replacing or expanding the drainfield. It must meet the same criteria, such as acceptable soils, setbacks, etc., as a regular drainfield and should be protected in the same way.

Learning about my property’s septic system

How do I locate my septic system? How can I learn more about my property’s septic system?
Obtain a copy of your property’s septic system record drawing (usually referred to as an “as-built”), a diagram showing where your system components are located. You can obtain your property’s as-built from your local health department or health district–some allow you to search for your as-built online.

How do I know my septic system is in good working order?
A septic system evaluation can be performed by a septic system professional. Some health departments and districts can perform this service, usually for a fee. Contact your local health department or district for more information.

Questions about septic system failure

What happens when a septic system fails? How can I tell?
Usually when a septic system fails, the drainfield is not functioning properly. When a septic tank overflows, the effluent can pass to the drainfield, clogging up the pipes. This causes sinks and toilets to back up in the house. Other signs include: slow draining toilets and drains, an odor of sewage, wet area on or near the drainfield, or contaminated well water.

How can I prevent a septic failure?
Maintenance, maintenance, maintenance! If your system has been properly designed, sited, and installed, the rest is up to you. Inspect your system annually and pump as needed (usually every 3-5 years), avoid excess water use, and watch what you put down the drain and flush down the toilet. For additional information, visit the “System Maintenance” page.

Can my septic system contaminate my well and nearby streams and water bodies?
Yes, particularly if the effluent is not adequately treated, as in a failing system. Untreated effluent is a health hazard and can cause many human diseases. Once this untreated effluent enters the groundwater, you and your neighbor’s wells can be contaminated. Also, if this sewage reaches nearby streams or water bodies, shellfish beds and recreational swimming areas may also be jeopardized.

Is there financial help available for failing systems or repairs?
Some health departments and districts in the Puget Sound region have low-interest loan and grant programs to help residents who live in shellfish protection areas or need financial assistance to maintain existing systems and repair failing septics. Visit the “In Your Local Area” page to access your local health department or district Web site for more information.

Everyday household use questions

Why is water conservation important?
Septic tanks are mainly settling chambers. They allow time for solids and scum to separate out from wastewater, so clear liquid can safely go to the drainfield. Over time, the scum and sludge layers get thicker, leaving less space and time for the waste-water to settle before passing to the drainfield. There are limits to the amount of water septic systems can treat. For every gallon entering the tank, one gallon is pushed out. In some instances, too much water may back up into your house or overload the drainfield and surface in the yard. Large volumes of water in short periods of time may also not allow solids enough time to settle, and may be carried out to the drainfield, ultimately clogging the pipes.

I’ve heard I shouldn’t use a garbage disposal. Why is that?
Garbage disposals have a dramatic impact on how often you’ll need to pump your septic tank. Food particles usually are not digested by the bacteria and accumulate as scum. If a large amount of water enters the tank, it can then push the food particles into the drainfield, causing clogging. If you must use a garbage disposal, your tank will need to be pumped more frequently.

Should I be careful of what I pour down the drain?
Yes, many materials that are poured down the drain do not decompose and remain in the tank. In addition to minimal use of a garbage disposal (see question above), don’t pour grease, fats, and oils down the drain or place coffee grounds and egg shells in the disposal or down the drain. Keep chemicals out of your system. See the “System Maintenance” page.

What shouldn’t I flush down the toilet?
Flush only human waste and toilet paper down the toilet—avoid flushing dental floss, cat litter (including “flushable” varieties), hair, Kleenex, cigarette butts, cotton swabs, feminine hygiene products, condoms, paper towels, static cling sheets, diapers, and disposable wipes. These items could clog your septic system components and cause a failure.

Will additives help my system?
No. Adding a stimulator or an enhancer to a septic tank to help it function or “to restore bacterial balance” is not necessary. The naturally occurring bacteria needed for the septic system to work are already present in human feces. According to the U.S. Department of Health, none of these products eliminate the need for routine maintenance and pumping.

Drainfield questions

What can I plant over my drainfield and septic system?
Grass is the ideal cover for drainfields. Grasses can be ornamental, mowed in a traditional lawn, or in an unmowed meadow. Or, you can try groundcovers and ferns (for specific plants, see the “Drainfield Landscaping” page). For plantings over septic tanks, keep in mind, if you don’t have risers installed, you will need to dig up the ground to access the tanks for inspection and pumping—generally every 3 to 5 years.

How close can trees and shrubs be to the drainfield?
Trees and shrubs generally have extensive root systems that seek out and grow into wet areas, such as drainfields. As a result, trees and large shrubs should be kept at least 30 feet away from your drainfield, and may require greater setbacks depending on the root structure and soil type. If you wish to plant trees near a drainfield, consult an expert who can determine types of plants and distances, based on your property’s soil type.

Can I plant a vegetable garden over my drainfield?
No. Growing vegetables over a drainfield is not recommended. Vegetables need watering, and excess water in the soil reduces its ability to treat wastewater. The deep roots of some vegetables may damage drainfield pipes. Bed preparation, such as rototilling or deep digging, can also damage pipes. Plus, there is the risk of contaminating food crops with sewage.

What about landscape plastic or fabric under mulch, can that be placed over the drainfield?
No. Plastic reduces the necessary air exchange in the drainfield soil. Even mulch or bark over the drainfield is not recommended, because it reduces air exchange and retains water.

Can I build a carport or camper pad over the drainfield? How about a tennis court or hot tub?
No, for two reasons. First, you should avoid driving over the drainfield– the pressure of vehicles and heavy equipment compact the soil and can damage pipes. Second, impermeable materials such as concrete and asphalt reduce evaporation and the supply of oxygen to the soil. Oxygen is critical to the proper breakdown of sewage by soil microorganisms.

How about putting my carport over the replacement area?
No. The designated drainfield replacement area (reserve area) should be left undeveloped and protected from compaction in case you must repair or replace your drainfield in the future.

Can cattle graze over the drainfield? How about just one horse?
Livestock should be kept off of drainfields. In the winter, livestock trample and muddy the soil; in the summer they compact it. Again, this is not good for the soil’s ability to exchange oxygen. So, sorry, even one horse is not recommended.

Rainwater is directed onto my drainfield, is this a problem?
Yes. Downspouts and stormwater from surfaces such as driveways and patios should be diverted off the septic tank and drainfield. A small trench uphill from a drainfield can help direct water away.

How close to the drainfield can I install a sprinkler system?
Water lines should be at least 10 feet from all components of the septic system. Be sure all sprinkler lines are fitted with approved backflow prevention devices.

…and can I put a retaining wall and drains back there?
If planning to put drains (interceptor, French, curtain) or retaining walls within 30 feet of ANY PART of the septic system, check with your local health department or district. Never cut through drainfields for drains, walls, or irrigation lines. French drains are notorious for carrying pollution from septic systems into water bodies or streets.

Inspection and pumping questions

I’ve been in my house for 18 years and never pumped my septic tank. Why should I be concerned?
Over time sludge and scum build up in the septic tank and unless it is removed it will flow into the drainfield, clogging the soil pipes. Once a drainfield is clogged, it must be replaced, which is an expensive repair, costing anywhere from $2,000 to $10,000 or more. It is also possible that you could have a leak in the tank. In either case, you risk contaminating ground and surface water resources, which could affect you or your neighbor’s wells or nearby streams and other water bodies. And finally, you may eventually have a plumbing backup in your home.

Can you tell if the tank needs pumping without digging it up?
Unless you have risers installed, you will need to dig up the ground above the septic tank to inspect it. Risers give easy access to the septic system without disturbing the soil above the tank. By keeping maintenance records, you can have it pumped on a routine schedule, based on the previous years’ rate of solids accumulation.

Who do I call to inspect and/or pump my septic system?
Contact your local health department or health district for a list of certified pumpers in your area—most have lists on their Web sites.

Can I inspect the tank myself?
Yes, you can inspect your septic tank using the “stick test.” You can find an online tutorial video produced by Island County Health Department at the “Inspection, Pumping and Repair” section of the Web site.

How often should I have the tank pumped?
How often you need to pump depends on the size of the tank, the number of people in the household, and the amount and type of solids. A septic tank should be inspected annually to check for needed repairs and pumped as needed, usually every 3 to 5 years. Some alternative systems that are more complex may need pumping more frequently. If you are unsure if your tank needs pumping, have it inspected and get a recommendation for how many years you can go between pumping. Write this schedule down on a maintenance chart or where you keep your maintenance records and stick to it!

How much will it cost to have it pumped?
Pumping can cost from $250 and up. We recommend contacting at least three pumpers and asking them a series of questions before choosing the best pumper for your needs. Visit the “Hire a Certified Professional” page to find a list of helpful questions to ask.

Do’s & Don’ts
Do ask questions!