Septic Tech: 3 Ways Tank Technology has Matured

The design and construction of septic tanks has improved to meet the demand for durability and watertightness.
Septic Tech: 3 Ways Tank Technology has Matured
A concrete tank is shown with a top seam and cast-in access risers.

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Change is one of the few constants we can expect. The onsite industry’s simplest device, the tank, is not exempt. The septic tank is the heart and lungs of an onsite wastewater treatment system. Once taken for granted, the tank has seen much change on the regulatory, manufacturing and applications fronts. 


Change No. 1: Tank materials

Tank materials are essential to proper function of the tank, and leakage is a major concern with tanks in onsite wastewater systems. As regulators recognized the importance of the tank in the performance of the overall system, it was also recognized that the tank must be watertight to prevent surface or groundwater from entering and causing hydraulic overload of the drainfield system and/or flushing solids out and causing the drainfield to be plugged. 

Conversely, if effluent leaks out, then untreated water can pose a health threat to surface or groundwater. Some states have enacted rules, which include watertightness testing.

While concrete is still the most common material for wastewater tanks, use of plastic and fiberglass tanks has become more common. Plastics and fiberglass are inert to wastewater constituents, a benefit for product longevity, and they are lighter, making them ideal for difficult-access sites. 

Due to new manufacturing technology, plastic tanks now offer increased strength as compared to plastic tanks of the past. Plastic tanks that are manufactured by the rotational molding process are typically a one-piece tank and thus minimize leak potential.

Additionally, plastic tank designs have been introduced with a new technology of continuous gaskets, which are common in the pipe industry, and the inclusion of a fixed, permanent connector system to lock the seam in place. 

In the case of concrete tanks, evolution includes tanks with top-seam joints to minimize the chance of leakage and the inclusion of additives or sealants to deter corrosion caused by hydrogen sulfide gases.


Change No. 2: Manufacturing process advancements

In most areas of the United States and Canada, codes still only state that a watertight tank shall be provided, but this is beginning to change, as some recent code alterations require testing to ensure tank watertightness. Best manufacturing processes and technological developments have been developed to meet the new requirements. 

These include the National Precast Concrete Organization’s Septic Tank Manufacturing Best Practices Manual, which explains, “With the increasing regulatory demands for structurally sound and watertight tanks, it is critical for precast concrete manufacturers to continually raise the bar on quality.” 

Advances in plastic manufacturing processes, including injection molding or rotational molding, have increased tank strength and durability due to the ability to include corrugations and ribbing to strengthen the tank. Interior structural bulkheads can now also be included to increase tank strength. 

Using the injection molding process enables manufacturing of larger tanks (1,500 gallons) that offer many benefits. The walls of the tank have a consistent wall thickness and the process allows for a stronger and lighter tank. And the tanks can be manufactured in halves, allowing nesting for increased shipping density.


Change No. 3: New uses for tanks

In septic system applications, the need for compact systems for small lots and for systems in environmentally sensitive areas is serving as a catalyst for tank innovation, including increased safeguards to ensure watertightness. Applications such as rainwater harvesting for non-potable and potable use are coming to the forefront of the tank design arena. 

Economics and the higher costs of a depleted resource like water are helping to increase the popularity of diverse tank designs and related applications. Also, a variety of needs for pump tanks, stormwater runoff storage tanks, and agricultural and chemical storage are catalysts for new tank designs.


The bottom line

Tanks serve many uses. While their function as storage vessels has not changed, every other thing surrounding the topic of tanks has changed, including the types of usage, the materials used, and the rules and regulations surrounding tank applications.


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