Underground Septic Tanks

Off-mains sewer: your septic tank is the workhorse the whole wastewater system relies on. RapidPlas supplies lightweight underground septic tanks under 150kg in poly, a tough, non-corroding alternative to concrete, certified to AS/NZS 1546.1 for safe, reliable on-site wastewater treatment. Browse the complete range.

Why Choose RapidPlas Underground Septic Tanks?

The RapidPlas underground septic tank is a 3,000L Australian-made design, moulded in tough poly that won't corrode or crack the way concrete can over time. An internal partition splits the tank into two chambers, settling and clarifying wastewater in stages before it moves through to your absorption trench. Sized for households of up to five people, they’re supplied ready to install.

  • Poly build, a non-corroding alternative to concrete.
  • Certified to AS/NZS 1546.1, the standard councils require.
  • Internal partition treats wastewater in stages before it reaches your trench.
  • Lightweight compared to concrete, easier to transport and place on site.
  • Backed by a 10-year manufacturer’s guarantee.

Choosing the Right Tank

Start with your household size, soil type and Council approval, then check each product for its capacity, specifications and warranty. Off-mains properties usually need water storage too, so browse our range of rainwater tanks. Contact our team or your local dealer to pick the right fit.

FAQs

Find quick answers to common questions. For further assistance, please contact our customer service team.

Yes, and often better for handling. Poly won't corrode or crack over time the way concrete can, and it weighs a fraction as much, which makes delivery and installation easier. Both poly tanks in the range are certified to AS/NZS 1546.1, so they meet the same performance standard councils require.

It comes down to how many people live on the property. Our 3,000L RapidPlas tank suits households of one to five people.

In most cases, yes. Installing an on-site wastewater system usually requires Council approval before work starts, and rules vary by area. A certified underground tank helps meet the standard, but you should confirm the approval process with your local Council first.

You'll need an excavated hole and a licensed plumber or drainer to install it. Because the tank is much lighter than concrete, it's easier to transport and position on site, but check with our team on what lifting gear is needed for your setup.