Holding Tanks for Tiny Home Sewage Disposal

A Tiny Home only needs a tiny lot of land, but it still has a full-sized toilet. Things still have to drain, like the kitchen sink, bathroom lavatory, shower, and clothes washing machine; and that toilet still has to be flushed. That flushed water and matter has to go somewhere. The typical nature and location of tiny homes generally means there won’t be a community or municipal sewage system for it to go to. The tiny lot of land will probably be too small to accommodate a traditional-style septic tank and drainfield. Enter the Holding Tank.

A Holding Tank is as simple as it sounds – a tank, like a concrete or fiberglass box, underneath the tiny house or buried in the ground. There are only two parts: [1] the sewage drain from the house; [2] the tank it connects to. The tank holds the sewage until it is full enough to merit a visit by a pumping service, which drops in a vacuum hose and sucks out the stuff. Pumping trips can be by subscription or à la carte. Usage will determine the number of pumping visits, whether the tiny home is for fulltime living or an occasional weekend getaway. Some situations may dictate that the holding tank be located uphill from the house. This will require the addition of a pumping station which includes an electro-mechanical macerator. But, the holding tank is still the final destination. 

Above: a diagram of a full-fledged, onsite sewage system. From left to right: drain field (leach field), multi-chambered septic tank, the house (source of sewage.) Omit the drain field and substitute a single chamber tank to create a stand-alone flushing destination, the HOLDING TANK.

Let’s explore the pros and cons of installing a holding tank for sewage control in a tiny home, along with the cost of pumping and maintenance considerations.

Pros of Holding Tanks:

  1. Low-Cost Installation:
    • Unlike septic systems, holding tanks don’t require extensive excavation or complex perforated pipe installations. This makes them more affordable to install initially.
    • Ideal for areas where septic systems are not permissible due to restrictive building codes.
  2. Temporary Solution:
    • Holding tanks can serve as a temporary solution for homeowners who wish to occupy a new dwelling before a permanent septic system is installed.
  3. Space-Saving:
    • Holding tanks take up less space than septic drainfields, making them suitable for tiny homes with limited land area.

Cons of Holding Tanks:

  1. Frequent Pumping:
    • Holding tanks need more frequent pumping compared to septic tanks. Since they don’t process sewage, they fill up faster and require regular maintenance.
    • If you plan to use the holding tank regularly, you might need to clean it every 6 to 8 weeks.
  2. No Sewage Purification:
    • Unlike septic tanks, holding tanks don’t leach wastewater into the ground. They merely store sewage until it’s pumped out by a vacuum truck.
    • There is no outlet pipe in a holding tank, so wastewater remains until removal.
  3. Professional Installation Required:
    • Setting up a functional and fail-safe holding tank involves evaluating site conditions, identifying sewage lines, and undertaking intricate piping tasks.
    • Professional installation is crucial to avoid issues like leaks and contamination.
  4. Regulatory Compliance:
    • Before installing a holding tank, obtain necessary permits from local health authorities. Present site plans, holding tank designs, and maintenance plans for approval.

Cost Considerations:

  • Installation Cost:
    • The price to install a septic holding tank typically ranges from $1,500 to $5,000 for a 1,250-gallon tank, suitable for a three- or four-bedroom home.
    • The cost includes the tank itself, which can vary from $600 to $2,100 or more, depending on the type.
  • Pumping Cost:
    • The cost to pump a holding tank depends on its capacity and your location.
    • For example, a 500-gallon tank costs about 40 cents per gallon, while a larger 2,000-gallon tank costs around 28 cents per gallon.
    • Expect to pay between $150 and up for pumping, depending on your area.

Remember that proper maintenance and adherence to guidelines will help prolong the life of your holding tank. Regular pumping and responsible waste disposal are essential for maintaining a functional sewage system in your tiny home.

Most septic tank service companies provide pumping services for holding tanks for tiny homes. It’s kind of a thing now. 😊 Service trips can be scheduled regularly or a la carte. 

Happy flushing!

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