Knowing how to size a septic tank or how to compute the needed size is necessary in building the proper system for a home.
Deciding on the appropriate septic tank size isn’t the place to try to save a little money with a smaller tank. Too small of a tank will almost certainly have to be replaced because an inadequately sized unit may actually lead to a large variety of problems, will constantly be a problem until it’s replaced, and can cost a lot for repairs and maintenance.
There are different factors that good septic tank companies use in knowing how much capacity is needed. These factors are often used to compute or calculate the proper or required size in a given household. The factors that are used in determining how to size a septic tank are:
1. Number or persons inhabiting the house or the number of people who will actually be using the restrooms and drains – This factor determines the size of a tank based on the projected usage or the amount of waste that each member of the household will actually contribute to the capacity. Each member is given an average amount of contributed waste; each projected waste contribution is then added to determine the capacity needed by the household. The capacity will then be used to determine the size of the septic tank.
2. Number of bedrooms in the house – This is also synonymous to the number of people in determining how to size a septic tank. This factor is made under the assumption that each member of the household will need or use separate bed rooms. Thus, calculating the number of bed rooms is like calculating based on the number of people in the family or the house.
3. The water usage – This factor in determining how to size is computed based on the estimated number of water gallons that an average person uses in a single day. Recent studies reveal that an average person uses about 171.8 gallons per day; this estimate is then used to determine size. Since too much water moving through the tank will prevent proper settling of waste material, water level is critical for the system, and since the tank is primarily a settling container rather than a storage tank, average water use per day is also a critical factor.
4. Pumping frequency – Pumping frequency is used to determine how to size a septic tank since there is an actual schedule set. This factor is a constant in the equation and based on the recommended pumping schedule. Essentially, since it’s recommended that tanks are pumped every 3 to 5 years, then all tanks need to have enough capacity to hold the waste for a certain number of people for at least 5 years. Theoretically, if the tank has enough volume to handle the water flow and the tank is going to be pumped more often than recommended, a homeowner could get by with a smaller tank, but it’s not recommended.
With all these factors, it’s much better to assume the worst case scenario rather than the best. For example, certain family members may use more toilet paper than necessary; sometimes family members share a room in the house; individual water use could easily be higher than average; and, being really responsible about pumping the tank is much easier said than done. By assuming the worst case scenario, you’ll be on the safe side and be more likely to avoid an expensive septic tank removal and replacement.
Other factors to determine how to size a septic tank may also be considered such local regulations and the use of water saving devices.