Understanding Private Onsite Wastewater Treatment Systems

As we’ve mentioned in past blog posts, the three main pillars of an offer to purchase are terms that are related to 1) Money 2) Timing and 3) Condition of the property.  While most general condition-related concerns are addressed through the general home inspection contingency,  there are a few items which are dealt with on their own terms:

• Radon
• Lead Based Paint
• Well Water
• Well Systems
• Private Onsite Wastewater Treatment Systems (POWTS)

Today we are going to focus on POWTS.  For many people this subject has been a normal part of home ownership as long as they can remember, while for others, it is a completely foreign concept, having spent most of their lives in homes served by municipal sewer systems.  

In the US, according to the US Census Bureau, more than 60 million people (about 26 million homes) are served by septic systems.  This represents about a quarter of the homes in America!  Naturally, when buying or selling a home with a POWTS, a general understanding of this very important home element is necessary to make clear and intelligent decisions.  

For those who grew up in the city, with sewer service, many of the terms related to POWTS are new and even confusing.  To make matters worse, (or better) septic systems are generally “out of sight, out of mind”, so many people don’t really think about them even while they are literally “right under their noses”.  Here is a short list of definitions to help us get started:

• Septic System: An onsite wastewater treatment system that has a septic tank for primary treatment and a trench or bed soil absorption system for secondary treatment of wastewater.
• Septic Tank: This is the primary tank where all water from sinks, tubs, showers, and toilets will flow after leaving the house.  In this tank, waste will separate into three layers: sludge, effluent, and scum.  Natural enzymatic action should work to break the sludge down into liquid form over time.
• Dosing Chamber: This is a secondary tank where the effluent from the septic tank is allowed to flow from where it is pumped to the distribution box and spread across the drain field.  
• Distribution Box: The distribution box moves effluent from the septic tank into a drain field.  The box has several openings for pipes that lead to the drain field and makes sure that the effluent is distributed evenly.
• Drain Field: An area which allows effluent to be distributed into the ground.  The wastewater makes its way through the drain field and is naturally filtered before it makes its way into the groundwater where it naturally cycles back into the water table.  In the soil, microbes perform the cleansing of the effluent from the septic tank. 
• Perc Test: Also known as a percolation test, this is a soil test that is performed before installing a septic system tank, which measures the level of liquid absorption the soil in the area of the proposed tank is capable of.  There is a minimum amount of absorption required before a septic system can be installed, and so failing a perc test could be catastrophic if you’re planning to build a new house on vacant land, for example.  For this reason, buyers of vacant land in areas without municipal sewar service would be well advised to make their offers contingent upon the sit passing a perc test. 
• Mound System:  In situations where the soil is unsuitable as a drain field, a mound system may be a solution.  A mound system consists of a normal septic tank, dosing chamber, distribution box, and a mound constructed above grade.  It is made up of a soil cover that can support vegetation and a fabric covered course gravel aggregate.  Into this aggregate is placed a network of perforated pipes to distribute the effluence into the gravel.  Building this mound can overcome hurdles to effective waste treatment: 
  • Soil is either too permeable or not permeable enough
  • Soil is a shallow layer over a creviced or porous bedrock
  • There is a high water table.

This blog isn’t meant to be a complete primer on the details and types of POWTS, but the EPA has a great website you can check out to learn more about all the various types and configurations in use in the US.  https://www.epa.gov/septic/about-septic-systems

In Wisconsin buyers may choose to make their offer contingent upon receiving a written report which indicates that the POWTS is in conformance with the code that was in effect at the time that the system was installed, and it is not disapproved for current use.  This contingency is part of the Addendum A document and can be added to the offer with a simple checkmark.   The language on the Addendum A is specific about who must provide the report: a county code administrator, licensed master plumber, licensed master plumber-restricted service, licensed plumbing designer, registered engineer, certified POWTS inspector, certified septage operator or a certified soils tester.  Unlike the general home inspection, the seller is responsible for the costs of obtaining the report, though the offer may be configured to reassign this cost to the buyer if so desired.  The POWTS is to be pumped at the time of inspection, and regardless of who is responsible for the inspection costs, the pumping costs are assigned to the seller. 

As with all other contingencies, timing is important.  In this case, the wording on the Addendum A will dictate two things:  A deadline for receiving the report (expressed in days prior to closing), and a maximum age of the report (expressed in days prior to closing).  Additionally, the buyer may or may grant the right to cure in the event that the POWTS fails inspection.  (you can read about right to cure in a related blog post).

The capacity of a home’s septic system is very important to know and understand.  When selling a home, the number of bedrooms is actually limited to the capacity of the septic system, regardless of the number of physical rooms the home may have.  For example, a home may have 4 physical bedrooms, but if the septic system is only rated for 3 bedrooms, the home may only be listed as a 3 bedroom home.  Listing as a 4 bedroom home could constitute a misrepresentation and open the seller to legal consequences.  There are various ways to find the capacity of a home’s septic system.  Perhaps the easiest is to reach out to the local municipality.  Since your septic system is (almost certainly) permitted, the municipality should have the information you need.  Alternatively, you can have a qualified professional conduct a detailed inspection of the system and provide you with an official report stating its capacity.  

Like all home components,  proper maintenance will greatly improve the lifespan of your septic system.  When selling a home with a septic system, it’s always a plus to be able to provide your service and maintenance records to potential buyers.  Because your tank will need periodic pumping, it’s also very helpful to be able to refer buyers to the company you employ for that service, since it will be one less thing for them to worry about.  Remember that many buyers for your home will have no prior experience with septic systems, so anything you can do to put their minds at ease and eliminate the septic system as a concern will be well worth the effort. 

Do you have any questions about septic systems?  We’d love to hear from you!