How To Look At A House
McGarry and Madsen's home inspection blog for buyers of
site-built, mobile/manfuactured and modular homes
How often should I pump out the septic tank?
Saturday, September 22, 2018
The standard recommendation for cleaning a septic tank is every four to five years. But it varies depending on the size of the tank and the number people in the home. Because septic tanks and drainfields are sized according to the number of bedrooms in a home, a 4-bedroom home will have a larger system than a 2-bedroom. And two people living in a 4-bedroom home will not have to pump their tank as often as four people living in a 2-bedroom house.
The septic tank and drainfield is a marvel of low-tech engineering. Liquid and solid waste flows into the tank at one end, with a vertical baffle in place at the center of the tank to keep anything from floating directly over to the outlet to the drainfield. The heavier solids separate over time, as anaerobic bacteria work on them, and settle on the bottom, becoming sludge. Meanwhile, the lighter solids migrate to the top as a scum layer. Wastewater is drawn out of the middle of the tank depth, between the two layers—free of solids—and flows into the drainfield.
But, if the tank maintenance is ignored for too many years, eventually the sludge and scum layers thicken until they meet at the center of the tank. Then solids begin to flow into the drainfield, clogging it to where it can no longer percolate the wastewater into the soil. The drainfield failure causes a backup of stinky wastewater into the home. At that point, simply pumping the tank is no longer an option. The drainfield will also have to be replaced, an expensive proposition that also shreds part of your lawn. So regular septic tank pumping is actually a cost-saving measure that we recommend. Some septic contractors offer a reminder service or will set up a schedule for regular pumpouts.
Also, see our blog posts What are the signs of a full septic tank? and What can I add to my septic tank to help it work better?
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To learn more about septic tank systems, see these other blog posts:
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