How adding a bedroom impacts your septic system

1200Health Departments often require you to install an entirely new septic system when adding a bedroom.  The following are some questions and answers that explain why and how an Aero Tech Aerobic Treatment Unit can come to the rescue!

Q:  “I want to add a bedroom to my house, do I need to increase the size of my septic system?” 

Most septic systems were installed to handle the home’s estimated flow with no extra allowance.    A home’s estimated wastewater flow is a function of the number of bedrooms in the house. Here in Indiana, our septic code specifies that each bedroom can be expected to contribute 150 gallons per day of wastewater to your septic system.  When adding a bedroom, even though the home’s occupancy and actual flow might not change, the estimated flow does.  When the number of bedrooms increases, it will likely attract a future buyer with a larger family (and higher wastewater flow).

This is why the health department will most likely require that you increase the size of your septic system when you increase your total number of bedrooms.

Q:  “I want to add a bedroom.  Why can’t I just increase the size of the field system by adding a few trenches to accommodate the new, fourth bedroom?”

Space constraints, perimeter drains and other obstacles often make adding to your septic system an impossibility.  The way mound systems are constructed really don’t lend themselves to expansions.  If your existing system is 15-25 years old, it is possible it “still works” but no longer meets code.   This means the health department probably won’t let you up-size the existing septic system anyway.

Your existing septic tank size may further complicate things.  Since most systems were installed with the minimum sized septic tank (1,000 gal. tank for a three bedroom house in most circumstances), increasing the number of bedrooms in a house would require a larger tank (or require adding a second tank in series with the first tank to bring up its capacity to handle the additional bedroom).

Q:  But my system is only a few years old.  Aren’t there any other options that would allow me to upgrade my septic system so I can add a bedroom to my house? 

I’m so glad you asked.

If you are adding a bedroom, you are often required to install an entirely new septic system to provide for the larger house.   Your other option may be to incorporate an Aero-Tech aerobic treatment unit with your existing system.   Adding this aerobic treatment unit to your existing system allows you to take the allowable 33-50% reduction in the size of your field system.  This means that your existing field system becomes large enough to accommodate the new bedroom addition.

Here are the reductions allowed in Indiana.

Note:   33% reduction in clay soils (loading rates of <.5)

50% reduction in sandy soils (loading rates => .5)

Q:  But what about the size of my septic tank, won’t it be too small? 

Aero-Tech ATUs  only require 24 hour retention in the tank upstream of the aerobic treatment unit.  That means that your 1000 gallon septic tank will be large enough for your home addition.    You will not have to put in a 1250 tank to accommodate your new four bedroom house.   In fact, a 1000 gallon tank will be large enough for up to a six bedroom home!   Why is 24 retention satisfactory when using an Aero-Tech ATU?  That’s because it’s how Aero-Tech ATUs  were tested and received their NSF 40 certification.

Tip: Please always use an effluent filter on your septic tank outlet.

Q:  Please explain where the ATU will be installed.  How big is it? 

Your new aerobic treatment unit will be installed directly downstream of your septic tank (between your septic tank and distribution box or between your septic tank and dosing tank).  The AT-500 and 600 units are cylinder shaped tanks and are 5.5 feet in diameter and about 7.5 feet tall (floor to top of riser).

Q:  Sounds good.  What is my next step? 

Be sure to talk to your local health department to see if downsizing your existing system with an Aero-Tech unit is an option.   Each septic system is different and it is possible that your system will not qualify.  When you get a go-ahead from the health department,  contact an Aero-Tech Certified Installer for pricing and installation details.

Feel free to CONTACT ME  if you have further questions.