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Except for part of South Woodstock near the fairgrounds, everybody in our town Flushing meadows.  Photo by Bet Zimmermancurrently depends on a septic system to handle their household wastewater. The greatest threat to water quality in Woodstock is not industrial or commercial pollutants, but "non-point" pollutant sources, such as failing septic systems and contaminated stormwater runoff.  The CT DEP estimates that every year about 15,000 septic systems may fail.


What is a Septic System?

A septic system is used to treat liquid wastes to prevent contamination of drinking water wells, groundwater, and nearby lakes and streams. 

A septic system typically consists of:

  • a septic tank, which is a watertight, buried tank made of concrete, fiberglass or plastic;
  • a distribution box; and
  • a leaching field (also called a bed, soil drainfield, disposal field, or absorption field), typically consisting of perforated pipe laid in gravel-filled trenches

all of which are connected by pipes, called conveyance lines. 

How does a septic system work?

  1. Wastewater flows from the house into the septic tank.
  2. The septic tank holds the water long enough for the solids to either be digested, or settle out as sludge.
  3. Scum and grease float on the top of the liquid, and submerged baffles prevent the floating scum from being discharged
  4. Liquid wastes overflow into the distribution box, which evenly separates the effluent into the network of distribution lines in the leaching field.
  5. In the leaching system, which may consist of a leaching field, trenches, dry wells, beds or galleries, the trickling water is further purified by filtration and decomposition by soil microbes, before it percolates into the groundwater.
  6. Properly designed, installed and maintained septic tank/leaching field systems provide excellent treatment, purifying wastewater into drinking water within a short distance.  A conventional septic system should last about 30 years. 

What can cause a septic system to fail?

If a septic system is not suitably located, properly designed, carefully installed, and adequately maintained, it can fail. It can also fail if solids clog it.  Failing systems can threaten your family and neighbors' health, reduce the value of your property, and cost a lot of money to repair. They can also contaminate groundwater, lakes, or streams with bacteria, nitrates, viruses, chemicals and chlorides.

Signs of failure include:

  • Wastewater draining slowly from the bathroom or kitchen fixtures.
  • Sewage backing up into the home, or puddling on the surface of the ground.  If the liquid effluent cannot soak into the soil surrounding the leach field, it has to go somewhere.  A "spongy" feeling in some areas of the leaching field, near the distribution box, or near the septic tank may be caused by water and waste being pushed to or near ground level. Ponding water (also called "breakthrough), is a fairly positive indication of failure of one or more parts of the system.  Note: backup can also be due to blockage somewhere between the house and the septic tank, which is relatively easy to fix.
  • Sewage smell outside the house.  If the smell is more noticeable after a lot of water has been put into the system, (e.g., after multiple showers or several loads of laundry), this may indicate that the leaching field is failing. The smell, however, can also originate at the plumbing vent.  In either case, further investigation is warranted. More info on odors.
  • Lush growth of grass above the leaching field.

Commons causes of septic system failure include:

  • Leaking fixtures or overuse of water.
  • Neglecting to regularly inspect and clean the septic tank.  If sludge or scum is allowed to escape into the distribution box, and from there into the leaching field, the soil will quickly become clogged.  If this happens, the liquid will no longer be able to soak (percolate) into the soil. Broken baffles in the septic tank can cause this condition. Failure to have the tank pumped can also lead to a situation where the sludge and scum overwhelm the baffles.
  • Lack of understanding on proper use of the system.  A septic system is not designed to handle solids.  If solids overflow from the tank into the leaching system, they will clog the holes.
  • Poor soil conditions and/or faulty design or installation.  A leaching system placed in unsuitable soil, a system that is too small for the house it serves, or an improperly constructed system, can lead to early failure.
  • High Water Table. During wet, or abnormally wet seasons, groundwater may rise into the leaching field and force sewage upward to the ground surface. This may mean the system needs to be re-installed at a higher level. It may also be possible to intercept the high groundwater with a series of drains around the system called "curtain drains."

How can you avoid problems?

Have your septic system inspected and pumped regularly.  Most problems can be prevented through simple maintenance by a licensed inspector/contractor.  Over time, solids will settle out in the bottom of the tank.  If they are not pumped out, they can plug up the leaching field, requiring costly repairs, impairing the ability of the soil to effectively treat septic tank effluent, and causing pollution.  A regular cleaning is not that expensive (about $130 to $200).  While the tank is open, the service technician can also run some water from a hose into the distribution box to determine whether the leaching field is still functioning.  Ask if the company offers this service.  Keep accurate records in a permanent house file on the location of the system, permits, and cleaning, inspection and repairs.  If you sell your home, pass this information on to the next owner.

 Also see the following list of Do's and Don'ts.



Woodstock Conservation Commission Direct all wastewater from your home into the septic tank. This includes all sink, bath, shower, toilet, washing machine and dishwasher wastewaters.  Any of these waters can contain disease-causing microorganisms or pollutants.
Woodstock Conservation Commission If the tank is 3-4 ft. below ground level, simplify inspection and cleaning by installing a 20-24 inch manhole about 12 inches below ground level.  Most recently installed tanks are just 6-12 inches below ground and this would make a manhole unnecessary.
Woodstock Conservation Commission Repair leaky faucets and toilets. One leaky faucet can waste as much as 700 gallons of water a year.
Woodstock Conservation Commission Use low-flow fixtures.
Woodstock Conservation Commission Educate your family on proper use of the system.
Woodstock Conservation Commission Spread out your laundry over several days to give the septic system more time to digest the water.
Woodstock Conservation Commission Run dishwashers and clothes washers only when full, and use the cycle with the lowest number of rinses.
Woodstock Conservation Commission Use baking soda to clean toilets, and boiling water and/or a mechanical drain snake to clear blocked drains.
Woodstock Conservation Commission Use non-phosphate laundry detergents.
Woodstock Conservation Commission Allow only grass to grow on top of the tank and leaching field.
Woodstock Conservation Commission Ensure that there is a vegetated buffer (grass, trees and shrubs) between your leaching field and a lake or stream.  They will suck up excess nutrients, help retain water, and prevent erosion.
Woodstock Conservation Commission Keep roof drains, surface water from driveways, basement sump pump drains, and other drainage systems away from the leaching field. 
Woodstock Conservation Commission Check with the local regulatory agency before installing a water softener that discharges to the septic system.
Woodstock Conservation Commission If your system has a flow diversion valve, learn its location, and turn it once a year.  This can add years to the life of your system.
Woodstock Conservation Commission DON'T flush even small amounts of paint, solvent, thinners, disinfectants, pesticides, or oils down the drain or toilet. These chemicals can destroy the bacteria that break down solids in the septic tank, and pollute groundwater.
Woodstock Conservation Commission DON'T use large amounts of laundry soap, detergents, bleaches, toilet bowl cleaners and caustic drain cleaners.  Recommended quantities should not adversely affect the system.
Woodstock Conservation Commission DON'T use chemical compounds, enzymes or septic tank "cleaners."  These can break down sludge, which can then flow into your leaching field, decreasing the life of the field.
Woodstock Conservation Commission DON'T discharge salt brine solution from water softeners.  CT Dept. of Health regulations prohibit this. Salt brine can build up in the groundwater and pollute wells and springs supplying drinking water.
Woodstock Conservation Commission DON'T allow excess amounts of fat or grease to enter the system.  It can congeal and cause obstructions.
Woodstock Conservation Commission DON'T use garbage disposals.
Woodstock Conservation Commission DON'T flush paper towels, tampons or sanitary napkins, condoms, plastic, or cat litter.
Woodstock Conservation Commission DON'T soak diapers in toilet bowl. A child may come along and try to flush the toilet.
Woodstock Conservation Commission DON'T put a lot of water into the system all at once.  Use water sensibly, and teach children to do the same.
Woodstock Conservation Commission DON'T use matches or an open flame to inspect a septic tank.  Gases produced by decomposing sewage can explode and cause serious injury.
Woodstock Conservation Commission DON'T allow trucks or heavy equipment to drive or park over the tank or leaching field.  Heavy equipment can crush the pipes and compact the soil so it can no longer filter and absorb sewage nutrients.
Woodstock Conservation Commission DON'T plant trees or shrubs on or near the leaching field.  Trees such as willows, poplar and sumac can clog up your tile bed and cause backup and surface seepage.

How often should you have your septic system cleaned?

Generally, sludge and scum should be cleaned out of septic systems every two to five years, depending on the size of the tank, and the amount and type of solids entering the tank.  A typical septic tank is designed to hold a minimum of 750-1000 gallons. (CT requires a minimum septic tank capacity of 1,000 gallons, and for a 4-5 bedroom house, 1250-1500 gallons.) As a rule of thumb, the cleanout interval is determined on the basis of 100 gallons of tank capacity per person, per year. For example, a 1,000-gallon tank used by a family of two should be cleaned after five years [1,000/(100x2)].  Using a garbage disposal increases solids loading by about 50%, which will mean you'll have to pump the tank twice as often. This is why use of garbage disposals with septic system is not recommended. Do verify that the cleaner is licensed by the State. In CT, you may also want to check to see whether the contractor is a member of the CT Sewage Disposal Association.

What do you do if your system fails?

If failure does occur, it is best to contact the local sanitarian or health officer, since pumping and cleaning alone may not solve the problem. If the system is clogged, you may have to have the system pumped down, not use it for 6 mos., or replace it (which may cost $2,000-8,000.) Woodstock residents should contact the Northeast District Department of Health,136 Main Street, Killingly, at (860) 774-7350 for instructions.  Keep records of your septic system design - the Town Sanitarian/Dept. of Health may have information, or a cleaner/installer who worked on the system may also have records. 


More Information and References:

This information has been excerpted and adapted from the following sources.  All information on this website is intended for your general knowledge.  You should consult with the appropriate regulatory agencies for specific requirements.  See the Woodstock Conservation Commission two-page handout summarizing  recommendations on this webpage.

Conservation Commission
It isn't pollution that's harming the environment. It's the impurities in our air and water that are doing it.

- Dan Quayle