QUESTION

When should I have my septic tank pumped?

ANSWER

In a previous column, I covered the information a service provider can give to homebuyers and homeowners, including a resource – The Homeowners Guide, which is available through the University of Minnesota Onsite Sewage Treatment Program and the Minnesota Extension Service – to help evaluate water-use patterns and determine septic tank pumping frequency.

A number of online columns by various “experts” of differing backgrounds have been brought to my attention of late, pointing out that “When should I have my septic tank pumped?’’ is one of the most common questions homeowners ask.

In one of these columns, a building inspector – not a septic industry professional –  answered the question by saying pumping every one to two years was a waste of money, five-year intervals seemed to be a reasonable number, and if a homeowner has gone 12 years without a pumping, a “septic contractor” should be called as soon as possible to evaluate the system. The writer further stated that bacteria levels in the tank can be maintained by dumping a product down the toilet on a regular basis.

MONITOR SCUM AND SLUDGE

When a homeowner asks me these questions, this is how I answer them: A properly operating septic tank should have three distinct layers. There should be a floating scum layer on top that is made up of soap scum, oils and grease that float on the surface; a clear liquid zone where the effluent is taken to pass on to the next system component; and a black sludge layer composed of undigested solids.

When the sum of the depth of the scum and sludge layers exceeds 25 percent of the operating depth of a tank, the tank needs to be pumped. So, for example, if the operating depth of a tank is 60 inches from the invert of the outlet to the bottom of the tank, a combination of sludge and scum layers measuring 15 inches or more indicates the need for pumping.

My discussion then turns to their water-use habits and patterns. I will point out that every family’s water usage is different. The number of residents in a home has an impact on how quickly scum and sludge layers accumulate. More people usually equates to more frequent pumping. Having water-using devices such as washing machines, dishwashers, water softeners and garbage disposals points toward having the tank pumped more often.

SEEK PROFESSIONAL HELP

If homeowners don’t do full loads in the dishwasher or laundry, or if they use the toilet as a waste paper and cigarette butt receptacle, they will probably not only need to increase tank maintenance but also require increased drainfield capacity to handle the additional water.

Regarding the comment about adding bacteria to keep the levels high in the tank, I would say the typical family adds bacteria through natural processes. While bacterial additives don’t appear to harm septic systems, they may not be necessary either. My advice to homeowners who want to try a bacteria additive is to work with a septic service professional to choose the product and monitor its effectiveness.

Over the years I have heard that homeowners are advised to add other things to the tank to build beneficial bacteria, such as dead chickens, rotten beef and – my all-time favorite – horse manure. Hopefully we are all quick to dispel these notions!

Where I live, the county sends a form every three years for my service provider to fill out that says they have either pumped the tank or inspected the contents and determined that – based on the scum and sludge levels – it does not need to be pumped. At the sixth year, pumpout is mandatory. From my experience, at least in Minnesota, three years is an average number for a full-time residence with average water use. The inspection option is present because a number of the residences and systems are only used seasonally or intermittently which means accumulation may be slower.

EFFLUENT SCREENS

One development over the last decade or so is the requirement of effluent screens. These are very effective at making sure that larger solids, wet wipes and other foreign objects that may be flushed do not end up in other system components or the drainfield. If the homeowner does not have an effluent screen, hopefully we are all suggesting that this is a good idea and it should be added.

Along with this recommendation, it should be pointed out that if things are flushed or solids are moving, they will accumulate on the screen (this is its purpose, after all). This will cause a backup when the screen becomes fully plugged. Smaller screens will plug faster than larger ones. If they don’t want a high-water alarm installed in their tank, maintenance service intervals should be shortened so the screen and tank can be inspected.

When talking to a new customer or new homeowner, it’s a good time to suggest that regular visits on your part would ensure their tank continues to operate properly and give them peace of mind. Perhaps start with a visit after six months just to see what is happening, and then lengthening time frames after they learn about how fast the scum and sludge layers develop and how to deal with plugging issues relating to the effluent screen.

I welcome comments about how you answer the question, “When does my septic tank need pumping?’’