Environmental Design Service

50 Jay Dee Lane
Birdsboro, PA 19508





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1.  Do I need a consultant to help in soil testing?

2.  What are septic certifications?

3.  Does Environmental Design Service do septic certifications?

4.  What is a percolation  test?

5.  How are septic systems sized?

6.  Do I have an option on the type of system I have to  install? 

7.  What can I do if my property is not suitable for any type of onlot system?

8.  What do septic tanks do?

9.  How do I take care of my system?


1.   Do I need a consultant to help in soil testing?

The answer is yes and no. In Chester, Montgomery, and Bucks Counties that are served by health departments who only observe the testing, you need to hire a qualified consultant or have the equipment and experience necessary to perform the testing.

In other areas, though a consultant is not a requirement, it can be very beneficial and cost effective for the following reasons:


  • Some systems require a Soil Scientist’s evaluation and if one is not present initially, testing will need to be redone at an additional expense due to excavation cost. 

  • Township Sewage Enforcement Officers are forbidden by law to plan or select the final system design in the jurisdiction they service.  A consultant is working directly for the client and has his/her best interest in mind.

  • A consultant can offer suggestions and options that can save expense by testing for the right system in the right place initially, rather than having to redo it later. 

  • Sometimes difficult sites require technical assistance, which is beyond the scope of some Township SEO’s lack of experience, equipment, etc.

2.  What are septic certifications?

These are inspections conducted to evaluate existing systems, typically done at the time of real estate transactions.  They are not regulated by any governmental agency and the standards differ from state regulations in terms of defining failing or malfunctioning systems.  The Pennsylvania Septage Management Association (PSMA), a trade organization has promulgated standards and practices in regards to these inspections and are generally used and accepted in real estate transactions.


3.  Does Environmental Design Service do septic certifications?

No.  Though we are trained professionals and can evaluate systems, we feel it is better to have an independent certifier who will not benefit from the outcome of the evaluation. 

We recommend certifiers who adhere to PSMA standards but do not install systems or do major repair work.


4.  What is a percolation  test?

A percolation test itself is just one part of a site evaluation process for determining site suitability for an onlot wastewater disposal system.

The process initially begins with a soil probe or probes dug by a backhoe to a depth of up to 7’.  The purpose of the probes is to determine the depth to limiting zones, which are either rock, water, or indications of poor drainage conditions.  This part of the evaluation normally determines whether a site is suitable for an onlot system and what type.  Some systems such as the drip irrigation, spray irrigation, or micromounds only require soil probes with no further testing needed.

The next step of the evaluation is the percolation test, which typically consists of six 6” diameter holes being hand dug or bored 12” to 36” deep in the area of the proposed area.  The procedure consists of an initial presoak of 12” of water in each hole the day before the actual test, a final one hour presoak, and then a series of readings at 10 minute or 30 minute intervals over a three to five hour period.  The final readings of the six holes are averaged and the rate is used to size the absorption area along with the proposed sewage flow.


5.  How are septic systems sized?

Based on the average percolation rate, or morphological rate assigned, and the proposed sewage flow, which is determined by the number of bedrooms for residences or type of use and number of people for other establishments.  Systems are sized by actual or proposed peak flow that is typically double the average daily flow.


 6.  Do I have an option on the type of system I have to  install? 

Yes.  Often times you have the choice of two, three, or more system types depending on your needs and site suitability.  We will provide you with information to enable you to make the best choice for your circumstance.  The sooner we are involved in the process (preferably prior to soil testing), the more options you will likely have.


7.  What can I do if my property is not suitable for any type of onlot system?

After carefully evaluating the site, we may offer solutions that may include stream discharge, dry stream discharge, four year fill, or holding tank.  We can assist in consulting and permitting for any of these options. 


8.  What do septic tanks do?

Septic tanks are passive, low-rate anaerobic digesters, with their own ecosystem and complex biological process.  As wastewater moves through the tank, beneficial bacteria breakdown complex proteins, carbohydrates, fats.  Within the tank, the wastewater separates into three layers.  The sludge layer on the bottom and a scum layer on the top.  The clear liquid  goes to your drainfield for final treatment and disposal into the soil.  If the septic tank becomes completely full of solids, organic matter will flow into the drainfield.  The drainfield will then form a thick organic mat and clog the soil, causing the sewage to backup or run over the surface.  This may require a new drainfield.  In order to keep your system healthy, please adhere to the following guidelines.


9.  How do I take care of my system?

The owner may extend the successful operation and life span of a sewage system with proper usage and regular maintenance.  The following recommendations will help to prolong the effectiveness of your onlot septic system.


1.   Area should be final graded, seeded, and stabilized as soon as possible after installation. 

2.   No harsh chemicals, paint, grease, cooking oils, lard, or other non-biodegradable materials, such as diapers or tampons, should be introduced into the system. 

3.   Garbage disposals are strongly discouraged for onlot systems.  Composting vegetable matter is recommended. 

4.   Water conservation is vital to the long-term operation of a septic system.  Low-flow showerheads, faucets, toilets, and front loading washing machines should be utilized. 

5.   Owner should measure distances of components of system, e.g., tank, distribution box, and corners of absorption area to fixed reference points to facilitate their location in the future. 

6.   Treatment tanks must be pumped out (from 20” lid, not 4” inspection port), when solids reach a depth of 1/3 or more of the liquid capacity of the tank.  All compartments and pump tank (if applicable) shall be pumped out.  The following chart provides the recommended frequency based on tank size and household population.  If a garbage disposal is used, tanks should be pumped out every two years.  Some municipalities have adopted ordinances specifying pumping and/or inspection intervals.  Owner should check with their local municipality to assure compliance.  Some systems have specific operation and maintenance requirements, which supersede this section. 


Septic Tank Pumping Frequency
Function of Tank Size and Household Population
(Assuming No Garbage Disposals)

Tank Size (gal)

2 people

3 people

4 people

5 people

900 gallons

5.2 years





























Source: The Pennsylvania State University Fact Sheet SW 161.



  • Do not drive, park, or store heavy objects over the onlot subsurface disposal area.

  • Do not connect cellar drains, sump pumps, or rain downspouts to the septic tank system.

  • Do not concentrate water usage, spread out high volume use throughout the week.  This would include eliminating washday and it would be better to run dishwashers and clothes washers on separate evenings or low water use periods.

  • Do not plant trees over or near the soil absorption systems.  Roots could clog or damage the drainage pipes.

  • In general, septic tank cleaners or enzymes are not needed for residential systems and by no means should this replace the regular septic tank pumping schedule.  In some cases, these cleaners cause the sludge blanket to be carried into the absorption bed, which causes the absorption area to become clogged.

  Never turn off an aerobic tank, even if you are going away for a short trip.



  • Properly use and maintain the system, which includes pumping the septic or aerobic tank, inspecting the system, cleaning laterals and/or delivery lines, and other maintenance items specific to the system.

  • Divert surface water and roof runoff away from the septic tank and soil absorption area.

  • Maintain records regarding the original site testing, permitting, design, inspection, maintenance, and repairs to the system.

Should your system exhibit any of the following signs of a problem:

  • Effluent surfacing over the absorption area on the down slope side.

  • Slow drains, frequent backups that are not caused by clogged pipes.

  • Foul odors or excessive vegetative growth over the absorption area.

We recommend that you contact a qualified professional to assess the situation such as our company, who stand ready to assist you.

Should repairs involve component replacement or additions to the system, contact the local Sewage Enforcement Officer (SEO) prior to any work being done to determine if permits are needed.


Environmental Design Service  ~  50 Jay Dee Lane  ~  Birdsboro,  PA  19508
  ~  610-582-0605
~ enviro@ptd.net