Jim Anderson, Ph.D., is an emeritus professor at the University of Minnesota Department of Soil, Water and Climate and recipient of the pumping industry’s Ralph Macchio Lifetime Achievement Award. Email Jim questions about septic system maintenance and operation at editor@pumper.com.
A reader wrote in with an observation about a practice he had seen lately and a question about system sizing based on the number of bedrooms. The reader said some installers tell homeowners the way around needing a bigger system is to have extra rooms without closets because they would not be counted as bedrooms. They argue that with fewer official bedrooms, they could install a smaller and less expensive septic system. The reader asked if I’ve seen a lot of these arguments and if ditching the closets really makes a difference.
The answer is yes, I have seen this before, usually in the context of inspecting systems for real estate transfers. And yes, it can make quite a difference in system size and, by extension, the cost of building a system.
I will use my family as an example to illustrate counting bedrooms and then look at some of the long-term implications of this type of approach. When our kids were still home, we had a four- to five-bedroom house. There was a master bedroom, a bedroom for each of the two children and two spare rooms. One spare room had a closet, and one did not. We called those rooms Jim’s office and Chris’ sewing room. When it came time to sell our house, the real estate agent walked through and said we could market the house as having five bedrooms, which means you will get more money because families with kids want them each to have a bedroom.
When I said we only had four bedrooms because the other one did not have a closet, the real estate agent said it would be very easy to add a closet to that room at little expense to the buyer. When the listing came out, there we were with a five-bedroom house. Great for us as sellers. It’s important to mention that the house we sold was on a municipal sewer system, so system sizing was not an issue.
SIZING IT RIGHT
It’s a different story when selling a home utilizing a septic system. As part of an inspection for a real estate transaction, information should be obtained on the current system size as it is permitted by the local unit of government. This information should then be compared to the real estate listing. Usually, the permit size will not match the real estate listing. The reasons for this are not always because of the purposeful intent to deceive, but due to additions made to the current residents by finishing the basement or loft areas resulting in an increase in the number of bedrooms.
People who buy a house based on five bedrooms versus three bedrooms usually have a reason to have that number of bedrooms. It usually means that kids or others are going to fill up those rooms. This usually results in increased sewage flows than for the current residents. Buyers need to recognize that since a septic system has a finite capacity and the design for the current system was based on three bedrooms versus five, the system is undersized for the expected flow. To put this in perspective, the difference in flow estimates based on 150 gallons per bedroom per day would be 300 gallons per day.
While those are design flow numbers, if the incoming family comes anywhere near those numbers it will lead to system failure not too far into the future. This creates the opportunity for lawsuits and recriminations. The time to catch this is at the point of real estate transaction so the buyer and seller can come to some agreement. Since the system is undersized, it needs to be either updated before the sale occurs or the price is reduced to cover the cost of enlarging the system.
ENLARGING THE SYSTEM
The increase from three to five bedrooms will require more septic tank capacity (usually 1.5 times), and that will involve replacing the current tank or adding an additional tank in series. The drainfield or other soil treatment component (mound, at-grade) will need to be enlarged by two-thirds. If the lot presents adequate space and suitable soil, this is not much of a problem. However, if the lot size is small or the soils on other parts of the lot are not suitable for drainfield trenches, the cost and difficulty will increase substantially.
The installer who advises not to take into account the number of real bedrooms is doing a disservice to both their current client and prospective buyers in the future. One or the other or both are going to end up paying for the difference, when putting in a properly sized system to begin with is the most efficient and cost-effective. Hopefully, after a few (one is too many) of these situations, local regulators get wise to the practice and work through a new standard to eliminate the practice.
