How Big of a Septic System Do You Need?

Posted on: January 30th, 2016 by admin 1 Comment

How big of a septic system do you need? It’s a question commonly asked by homeowners who want to either replace or expand their septic system. The easiest answer is that the size of septic system you require will depend on the amount of water your household uses. Here are a few tips to help you figure things out.

Consider any minimum size requirements in your jurisdiction. First and foremost, keep in mind that some jurisdictions do have a minimum size requirement. In most cases, if there is a minimum size requirement it will be 1,000 gallons. Keep in mind that the capacity of your septic tank should always be about 40 percent large than the quantity of sewage flowing into it on a daily basis. Or, in other words, the daily sewage flow shouldn’t be any more than 60 percent of the tank capacity. Therefore, a 1,000-gallon septic tank can typically handle around 600 gallons of sewage per a day.

Consider how many people will be using the system. When estimating your water usage to try and figure out how big your septic system should be, you need to consider how many people will be using the system. So of course, you will need to consider how many people are living in your household. If you have six people living under your roof, you will inevitably use more water and need a bigger system than a household of just two people. However, you will also want to take into consideration any visitors, including the number of visitors you have in a year and the frequency of these visits. So if there are only two people in the house but your sister and her three children come to visit for a week at a time several times a year, you might need a slightly larger tank.

Consider the age of the people living in your household. When choosing an appropriate size for your septic system, it is important to keep in mind that children inevitably use more water than adults. The average adult commonly uses somewhere between 50 and 100 gallons of water per a day, depending on bathing habits, laundry habits, etc. However, a baby will typically use a minimum of 100 gallons of water per a day. Therefore, children will increase the demand on your septic system.

Consider how often you engage in activities that use water. From flushing the toilet to running the dishwasher to doing a quick load of laundry, you will inevitably engage in actives that use water as you go about your daily life. To get an accurate reading of your water use, consider how often you engage in activities that use water:

  • Automatic washer: 30 to 50 gallons per load
  • Dishwasher: 7 to 15 gallons per load
  • Garbage Disposal: 4 to 6 gallons per day
  • Shower or tub: 25 to 60 gallons per use
  • Toilet: 4 to 7 gallons per flush

The measurements above can be used to help you figure out water use, though this is by no means a surefire way to come up with a completely accurate reading.

The bottom line is that the size of your septic system will depend on the amount of water you are using. Getting an accurate measurement of water usage is key, because if your septic system is too small to accommodate your usage, the waste retention time in the tank won’t be long enough and settlement will be insufficient. This, in turn, will reduce the life of your soakaway system, which could lead to costly repairs down the line. Therefore, accurately measuring water usage is key.