Cost of treating sewage: Septic vs Public Sewer vs Tight Tank

I had our septic pumped today and something about the smell in the air inspired me to write this post. 🌹

Parameter: 2-person household.

Disclosures:

  1. I have no way of knowing what my water consumption is since homes on septic do not have meters. MA DEP and EPA generally cite ~55 gallons per person per day as the average residential indoor water use- I’m assuming 110 gallons per day consumption in this 2-person household scenario. 3,300 gallons per month.

  2. Littleton does not publish its sewer rates (only water). To avoid confounding, I’m using Concord’s fee schedule as it’s got a clear distinction between water and sewer fees.

  3. Total septic system failure is costly, but so is a sewer hook up. My numbers do not account for installation costs.

Here’s a comparison of the monthly costs of treating sewage in a septic vs sewer vs tight tank.

Septic tank

We’ve got a 1,500 gallon tank and were advised to pump it every 2 years.

Paid: $425 (2023 - 2025)

Monthly charge: $425 ÷ 24 = $17.70

Public Sewer

Sewer charges are often cited by cost per cubic foot. 1 cubic foot = 7.48 gallons.

Sewer rate: $0.1431/cubic foot

3,300 gallons per month is equivalent to 441.18 cu ft.

Monthly charge: $0.1431 × 441.18 cu ft = $63.13

Tight tank (aKA Septic Holding Tank)

Tight tanks are rare in MA. If you’ve ever come across this term when purchasing or leasing a home, please do yourself a favor by looking it up.

“Holding tanks and septic tanks work differently. Both systems receive your home’s sewage, but holding tanks offer no treatment and have no outlet. They store raw wastewater until a pumper removes it.”

My septic company, R.J. Lacombe, charges $0.23 per gallon for residential pumping.

Monthly charge: $0.23 × 3,300 gallons = $759

Conclusion

The data speaks for itself.

Why are tight tanks even in existence, you ask? Well, public sewage infrastructure isn’t available to all households in America, for one. Two, some soils may not percolate and support a septic system. Three, tight tanks are a last resort for homes in environments that can’t afford to have risk of bacteria spread: near a water body, drinking water supply etc.

If you do come across a home with a tight tank, know that an average size of a residential tight tank is 4,000 gallons. Run your numbers, and be all the way sure.

InvestingJoan BissdorfSeptic, Sewer, Tight TankComment