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What Is a Septic Tank Riser?

Klaus Strasser
Klaus Strasser

A septic tank riser is an extension that sits on top of a septic tank making it more accessible. Some septic systems are designed with risers from the beginning; this is particularly true in places where the tanks are installed in very cold ground or in environments that are particularly harsh or corrosive. They can also be added by consumers later, and are sometimes even sold as do-it-yourself kits. Most of the time, risers are made specifically for certain sizes and models of tanks, and depending on the situation, they may even need to be custom-made. In order to be effective, they need to fit the existing septic lids exactly; this is a situation where models made for different tanks aren’t usually interchangeable. Risers can be made from a variety of different materials, though the most common tend to be polyvinyl chloride (PVC), concrete, and polyethylene. Some materials are better suited for certain situations than others, and can come with different cost considerations, too.

Septic Tank Basics

A septic tank riser generally refers to a specific type of extension that is added to a septic tank.
A septic tank riser generally refers to a specific type of extension that is added to a septic tank.

There are a couple of different options for sewage treatment, but in places where it isn’t practical or possible to connect to a larger municipal sewer system, a septic tank can provide an alternative. Septic tanks are basically large underground storage systems that house everything flushed down the toilet in the house or building to which it is connected. Bacteria inside the tank consume some of the waste as it sits, but some of it, particularly the solids, tend to accumulate over time and typically have to be manually pumped out to keep the system working efficiently.

Pumps usually connect to the top of the tank through sealed septic lids. They suction the solid contents out into a truck or other sealed receptacle so the waste is never actually exposed to the air or outside environment; it stays completely contained. Depending on the size of the tank and how heavily it’s used, pumping may have to happen fairly regularly. Having a riser often makes access a lot easier, and usually also faster as well.

Primary Benefits

The main purpose and benefit of a riser is to raise the height of the septic tank lid. In most cases lids are locked onto the top of a septic tank, and are held down by stainless steel screws. Some risers may also include structural ribs. This can be helpful in areas where winter is harsh, as the ribs prevent the build up of frost; frost can destroy or corrode the riser over time. Building codes and regulations in many places require risers for tanks above a certain size, which is also a consideration.

How They’re Manufactured

Risers are usually specially manufactured since, to be effective, they have to fit the precise dimensions of the tank over which they are fitting. They generally range from six inches (15.25 cm) to 12 inches (30.48 cm) in height, and have a diameter of between 12 (30.48 cm) and 24 inches (60.96 cm). Many are also made so that they can be stacked one on top of another. This is ideal if a septic tank is buried deep underground.

Choosing Between Different Materials

Some of the common materials for risers include PVC, concrete, and polyethylene. Concrete risers are among the most durable and inexpensive to manufacture, but they can also be very heavy, which in many cases makes them rather difficult to install. This often means that heavy lifting equipment is needed for installation. These risers may also be more prone to damage and leakage, and they aren’t usually very aesthetically pleasing.

A polyethylene septic tank riser has the advantage of being resistant to corrosion. Gaskets seal this type of riser, making the unit more secure. Polyethylene typically also prevents foreign materials from getting into the tank, and can reduce the chance that any dangerous gases, such as methane, will leak from it.

A PVC septic tank riser is usually the lightest of all options, at least when it comes to weight. This type can be much easier to install and requires less effort from workers. PVC risers are sealed much like the polyethylene models. This also prevents any leakage or entry of materials into the septic tank.

Cost Considerations

Septic tank risers can vary in cost. Some of the calculation centers on the material, but things like riser size and tank specificity also enter in. Models that have to be custom made are usually much more expensive no matter what they’re composed of. It’s also important to note that, while risers can improve access and may lengthen the useable life of the tank itself, installing one is not a substitute for regular maintenance and preventative care.

Discussion Comments


the only problem is acquiring risers. No one in the industry carries them in stock and shipping is prohibitive. Its a baited game where the DIY consumer always loses. Of course, in this economy, there will be NO one to sell them to anyway, so they lose too.


excellent explanations for people who are not mechanical!

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    • A septic tank riser generally refers to a specific type of extension that is added to a septic tank.
      By: gozzoli
      A septic tank riser generally refers to a specific type of extension that is added to a septic tank.