Septic System as a Key Element of a Modern ADU

With the scarcity of housing in the US, the question of using the full potential of the already existing property has never been that acute. Instead of buying new houses, more and more Americans opt to take advantage of their housing units in any possible way, and here, novelties like accessory dwelling units (ADUs) come in handy. At the same time, the building of your own ADU coincides with numerous difficulties like collecting the necessary permits, calculating the needed amount of space on the lot, and possible options of enlarging the current house.

At the same time, the ADU septic system remains an issue that is often overlooked by homeowners. However, they require careful planning if you want your own ADU. Therefore, every landlord planning their accessory dwelling unit needs to understand the intricacies of implementing a proper septic system.

Here we will discuss what a septic system means, what to look at during the installation, and the implications that an improper septic system may lead to. So, let’s delve into this difficult but exciting topic together!

Understanding Septic Systems

Imagine that you have a fully functioning ADU, with all the needed rooms including the living room, bedroom, and bathroom, with all the needed structure and worthwhile systems. You want to use the bathroom, go there, and turn on the tap. Where do you think the wastewater goes? If you’re lucky enough or had the opportunity to have the unit connected to the city sewer system, it goes right there. Otherwise, the unit needs a standard septic system with necessary septic tanks that will store and process the water, hence saving environmental health.

A regular septic system consists of just two main elements: a septic tank and a drainfield or leach field. The first one represents a buried underground watertight container made of different materials, for example, concrete, fiberglass, or polyethylene. Having left your unit, the wastewater goes right there. Bacteria residing in the tank start processing the organic matter in the water to make it easy to dispose of.

The latter, the leach field, is the next stop for the water. It includes perforated pipes buried on your property. The treated wastewater flows through the pipes and goes into the gravel, sand, or any other soil you have on your lot. Here it acts as a filter and treats water even more, allowing its access to the groundwater system. Overall, this whole system is an ingenious solution to the problem of wastewater that does not require any involvement from the city officials. You don’t spend any money on their services with your own structures, and your residents get an opportunity to lead a waste-free lifestyle.

Options When Choosing Your Septic System

Just like with every tiny element of the ADU construction, there are different options of septic systems to choose from when picking one for your new accessory dwelling unit. Even though the whole installment process isn’t that long, you need to assess beforehand which septic system fits you better.

Leach Field

The so-called traditional septic system has conquered the hearts of a significant number of homeowners because of its eco-friendly method of water management. As we have already described leach fields, this option allows safe liquids to go into the soil through the pipes. This is a rather cheap option, but the obvious drawback is the complexity of the system, which takes up much underground space on your lot. As a consequence, it is impossible to install such septic systems next to the primary dwelling.

Vertical Seepage Pit

This option mitigates the potential drawbacks of the previous option, allowing you to install a large concrete cylinder instead of a complex system of pipes underground. This cylinder is located in a pit of six feet under the soil level, which allows the bacteria to dispose of all waste. At the same time, it may be impossible to install it on your lot because of the strict regulations concerning this option. Your unit should be located next to the seashore, which will eventually allow the streams of saltwater to mix with the groundwater to start the purification process. However, if you fit the criteria, you can apply for this wonderful option and have it installed.

Horizontal Seepage Pit

Almost the same description goes for horizontal options that you can obtain and connect your unit with. It is still a concrete cylinder but placed horizontally under your lot. It is worth noting that the required setbacks here are strict and such an addition needs soil of good quality on your lot to successfully drain used water. What is more, such pits are more expensive than their traditional counterparts in the form of leach fields.

To conclude, the final choice of a system for your additional and, perhaps, primary residence, depends on the budget, site evaluation results, and needed septic capacity. The entire process is quite a complex task, so in order to avoid any possible headaches, it is utterly important to make the choice wisely.

Septic System Requirements

Apart from determining the cost and getting the necessary approval from the local authorities, it is important to understand the key requirements of a modern septic system so it can function effectively.

When choosing the septic system, pay attention to the following elements:

• As you may have noticed, the cost of septic systems varies drastically, depending on the amount of water they can process. Even if you have got an already existing septic system with a proper septic tank, you may need to enlarge it to increase the capacity because of an increased number of dwellers who will use the system.
• Capacity is important, but the suitability of your lot also plays an important role in this matter. A variety of factors like soil type, drainage, or even groundwater level influence the system you will need. A professional that you definitely will hire at one point or another can assess the soil and recommend a certain system that will be beneficial for your site.
• Just like with your ADU project, here you also require a set of permits from the local officials. It may be even more complicated as the rules vary from rural areas to large cities. Anyway, no matter where you live, it is vital to contact your health department and obtain the building permit. Moreover, there you will figure out the size limits, setbacks from property lines, and water sources. This will allow your septic system to comply with the law and safety standards as well.

All in all, you better keep in mind these considerations as they all contribute to the successful implementation of your septic system.

Necessary Documents for Septic System Installation

As we have discussed before, apart from the installment and maintenance costs, you also need to get permits. The process may take longer than normal if you don’t follow the critical steps.

The general roadmap for getting papers includes:

1. Contacting the local health department and figuring out the requirements for a system
2. Scheduling a site evaluation with a professional who can make it clear whether your lot is suitable for a septic system
3. Designing the system fitting feasible requirements
4. Submitting the design
5. Getting the successful approval with permit issuance right after

Overall, every new system will go through these steps, even though the details may differ.

Frequently Asked Questions — FAQ

Do all ADUs require a new system for used water?

Your new accessory dwelling unit may be connected to the already existing septic system if you have one for your primary residence. For sure, it is not a mandatory requirement for any new ADU project and you may even connect your new ADU to any alternative system including the municipal sewer system or just public sewer in California. So, choose carefully before making an agreement with your septic contractor.

How do we measure the needed septic capacity for an existing house and an ADU?

You can determine the size of the tank rather easily, as the calculations here are not rocket science at all. Think of the existing system and the amount of water your family consumes, count the bathrooms you will have in your house and an ADU, and imagine the structure your tank will have. As a result, you may have a vague understanding of all the water that will be processed. However, do not forget about professional help and proper testing of the project before the construction.

What considerations should I keep in mind before installing the septic system?

Before you produce a clear plan for the construction of the septic system, you need to assess your property in California carefully. It includes the amount of underground space on your lot, the accessibility of the driveways, the size of an ADU in the project, construction costs, distance from the main house, and building time. All in all, a septic system is a great alternative system for your new ADU that costs a little but provides significant benefits to the owner.