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Home Inspector

Septic System - hydraulic load test
July 2009

Last month I received a letter from Karen who works in Quakertown. Her question was in regard to on-site sewage systems which are much more prevalent in our rural areas.

"I have heard the terminology of 'hydraulic load test' used often in real estate transactions pertaining to septic systems. What is a hydraulic load test, and when is it recommended? Is a hydraulic load test fair and accurate? "

As Tri-County does not perform on-site sewage system analysis, I forwarded this question to Rob Bowie, who founded Bux-Mont Inspections in July of 1996. Rob is currently a Pennsylvania Sewage Enforcement Officer #02933. He is also a PSMA Inspector #0167 and is on the Education Committee and Standards Revision member. He has a B.S. in Environmental Engineering and a minor in Soil Science. He has been working full time in the profession since June of 1992, and can be reached at 215-669-4213 or via email at: bmseptic(at)comcast.net. Bux-Mont and Tri-County Inspection Company have enjoyed a professional relationship for over ten years. Below is Rob's response.
Jack H. Milne, Jr. President, Tri-County Inspection Co.

The Pennsylvania Septage Management Association has established a protocol for performing real estate septic inspections approximately 20 years ago with assistance from Penn State University. The PSMA is the equivalent for septic inspectors as ASHI is for home inspectors. However thus far, no local, county, or state government endorses the PAMA for inspections. A septic inspection is most accurately performed when the house is fully occupied. Liquid levels within a septic system are observed based on current household usage. Reserve capacity is determined, rendering a septic inspection result.

However, when a house is vacant, no fulltime water usage is generated from the house to the septic system. Therefore, the septic system is now dormant and very difficult to inspect. The hydraulic load test is a diagnostic inspection technique used for vacant households. The hydraulic load test uses an assumed full daily flow rate generated from the house for an induction to the system based on current state regulations for designing new systems. For example, a three (3) bedroom house is assigned a flow rate of 400 gallons per day. A four (4) bedroom house is assigned 500 gallons per day. This full volume of water is induced into the septic system at one sitting for two consecutive days. A flow chart would be as follows:

Three bedroom house=400 gallons per day flow rate
-Day one: induce 400 gallons into the septic system, observe elevations of water within system -Day two: induce 400 gallons into the septic system, observe elevations of water within system
If, during the load test, the water reaches a certain elevation within the system before full volume induction, the test is terminated and an "unsatisfactory" result is given. Hence, the septic system is expected to process this full daily flow at one single induction.

Is this fair or an accurate inspection technique?
Currently, we are introducing our new "SPLIT LOAD TEST" to the PSMA for consideration. The split load test attempts to mimic real life usage produced from a house. Typically, houses generate two peak flows of water, one in the morning before work and school, and the second after work and school. Our goal is to have the hydraulic load test mimic real life usage more realistically than presently practiced, specifically with pre-1975 septic systems on restrictive lots. This idea is a work in progress, and will be presented to the PSMA this October in Allentown when the education committee meets for protocol revisions and additions. If you have any additional questions or comments, please do not hesitate to call or email us.

If you book your inspection through Tri-County Inspection Company and require an on-site sewage evaluation, we can make these arrangements with Rob of Bux-Mont for your convenience. I feel that it is critical to have the client on-site while Rob is conducting his evaluation so that all questions can be answered.