Alternative septic system
An alternative septic system, called an alternative onsite sewage system in Virginia law, is a treatment works that is not a conventional onsite sewage system and does not result in a point source discharge. A typical one adds a treatment unit and a pump chamber ahead of its absorption field.
Not conventional, and not discharging
Virginia defines the alternative system by what it is not, and the definition has two halves.
a treatment works that is not a conventional onsite sewage system and does not result in a point source discharge
Va. Code 32.1-163, definition of alternative onsite sewage system
The first half points at the conventional septic system, which the same section defines as one or more septic tanks with gravity, pumped or siphoned conveyance to a gravity distributed subsurface drainfield. A system that treats sewage onsite in some other way falls outside that definition.
The second half separates it from a category with a similar name. Virginia law also defines an alternative discharging sewage system: one that results in a point source discharge of treated sewage, permitted for an individual single family dwelling with flows of 1,000 gallons per day or less. An alternative onsite system, by definition, makes no such discharge. The words overlap; the categories do not.
| Category | What the Code describes | Where treated sewage goes |
|---|---|---|
| Conventional onsite sewage system | One or more septic tanks with gravity, pumped or siphoned conveyance | A gravity distributed subsurface drainfield |
| Alternative onsite sewage system | A treatment works that is not a conventional onsite sewage system | Not to a point source discharge |
| Alternative discharging sewage system | A system permitted for an individual single family dwelling with flows of 1,000 gallons per day or less | A point source discharge |
Parts you can see from the yard, and an operator who keeps coming back
The difference often shows in the yard before anyone reads a permit.
VDH describes a typical conventional system as a sewer line, a septic tank, a conveyance line, a distribution box, header lines and absorption trenches, most of it out of sight. A typical alternative system adds a treatment unit and a pump chamber, and VDH says these systems usually, but not always, have components visible at the surface. Visible parts are a reason to ask which kind of system is there, not proof of the answer.
The larger difference lasts as long as the system does. Under 12VAC5-613, whose operation and maintenance part applies to every alternative onsite system, including those with applications filed before December 7, 2011, the owner must have the system operated and maintained by an operator and keep the operator's log and the O&M manual on the property. What that involves year to year is taken up in what an alternative septic system is and what owning one takes.
When a listing calls the septic engineered or alternative
Property descriptions use loose words for these systems. The statute's two-part test is what sorts them.
Engineered and alternative both turn up in listing copy, and neither adjective is a category by itself. The question underneath is whether the system is conventional as the Code defines it and, if not, whether it discharges. The system's operation permit, and the O&M manual and operator's log the owner keeps on the property, are the natural place to start.
Where a conventional system will not fit a site, alternative systems become part of the conversation, which is the subject of building on land that failed a perc test. What a well and septic mean when the property sells again is taken up in whether a well and septic hurt resale. How any septic system works from the tank to the field is in septic systems explained.
Does your listing describe the septic as alternative or engineered?
Send the address and the permit or manual you have, and Lowell will match the paperwork on hand to what a buyer will ask to see. No cost, no obligation.
Got it. Thank you.
We'll be in touch shortly with an honest read.
Questions about this term
Is an alternative discharging system the same thing as an alternative onsite system?
No. Virginia law treats them as separate categories. An alternative onsite sewage system is a treatment works that is not conventional and does not result in a point source discharge. An alternative discharging sewage system does result in a point source discharge of treated sewage, and it is permitted for an individual single family dwelling with flows of 1,000 gallons per day or less.
Does an alternative system from before December 7, 2011 escape the maintenance rules?
No. 12VAC5-613 says its operation and maintenance requirements apply to all alternative onsite sewage systems, including those with applications filed before December 7, 2011. Whatever the permit date, the system's operation permit and its O&M manual are the documents that describe what that particular system requires.
Where this page's facts come from
Every rule, office and figure above traces to one of these. Rules change; check the office before you act on one.
- Va. Code 32.1-163: definitions of conventional, alternative onsite and alternative discharging systems Code of Virginia
- 12VAC5-613-30: scope of the alternative onsite sewage system regulations Virginia Administrative Code
- 12VAC5-613-140: owner requirements, the operator's log and the O&M manual Virginia Administrative Code
- AOSS Operation and Maintenance FAQs Virginia Department of Health
- Onsite Sewage System Owner Responsibilities Virginia Department of Health