Hi, this is Bill Freeman with Freeman’s construction. I’m here on a job in El Cajon and we are installing the septic system. This system is a little bit different than the conventional system because the leach field sits at a higher elevation than the building pad. Many of these ADU lot require a creative septic system to be installed. This particular system, as you can see, had two tanks right here.

Using a Surge Tank

The first tank that you see is the normal septic tank with two compartment tanks. As usual, everything goes into that tank. The effluent that normally runs out into the leach lines now goes into this pump tank instead. We will install a line in that trench that you see going up the hill. That line will connect into another tank called a surge tank. The surge tank will be above the elevation of the leach lines we’ll install. From that point, the effluent gravity-feeds out of that tank up there by the leach lines, and flows into the leach lines, and then performs exactly the same as if it were flowing directly out of the septic tank. This optional system allows us to install septic on a piece of property that typically would not allow for an additional dwelling unit.

Before the Rain Comes

Our septic guys will finish installing the lines today, and then back fill everything before the rain comes. Rain will carry silt into the trenches, and silt seals off the dirt, which prevents the effluent from percolating down into the ground.


I’ve moved up here to the top. I want to show the infiltrators that we install in these trenches. Rather than perforated pipe and rock, which has been used for decades, these infiltrators are a dome shaped liner that sits on the bottom of the trench. We began using these several years ago. They make for a much cleaner and higher volume of leaching for fluid release into the ground.


To recap, we will have these lines here and over there, we’ll install the surge tank on that end, and then the effluent will go into that. There will be a tight line, which is a non-perforated line, that comes down and ties into this end right here, and in between, there will be another line that connects the two together as it drops down the hill.

Thanks for watching and have a great day.

Related Episodes

Thinking about building or remodeling your home?