What a septic tank riser is and why you might need one

A septic tank riser is a cylindrical extension that raises the access cover of your septic tank closer to ground level, so you don't have to dig down three or four feet every time the tank needs pumping or inspection. It's a PVC or concrete pipe that sits on top of the tank opening and brings the lid up to within a few inches of the surface. If your septic cover is currently buried deep, installing a riser makes maintenance easier and safer for the pumper truck operator.

Most risers are 12 to 18 inches tall and come in diameters matching your tank opening—typically 18, 24, or 30 inches. They're not required by code in most places, but they're practical if you plan to stay in the home long-term and want to avoid the cost and mess of excavation every three to five years when pumping is due.

Key Takeaways

  • A septic tank riser is a pipe extension that brings your tank's access cover closer to ground level, eliminating the need to dig for routine maintenance.
  • You'll need to know your tank's opening diameter and depth before buying a riser, and you should locate the tank with a probe or by reviewing your septic system documentation.
  • Installation involves excavating to expose the tank lid, removing the old lid, setting the riser on the tank opening, sealing it with PVC cement or a rubber gasket, and installing a new cover.
  • If your tank is very deep, you may need a two-piece riser or multiple sections stacked together to reach ground level.
  • This is a project many homeowners can do themselves, but if you're uncomfortable digging or working around the tank, a septic contractor can install it in an hour or two.

Locating your tank and measuring the opening

Before you buy anything, you need to know exactly where your tank is and how wide the opening is. If you have your septic system permit or inspection report, it will show the tank location and dimensions. If not, you can locate the tank by probing the ground with a metal rod or a thin PVC pipe—push it down until it hits something solid, usually 3 to 5 feet below the surface. Mark the spot and probe around it in a grid pattern to find the edges of the tank.

Once you've found the tank, measure the opening diameter. Most residential tanks have openings of 18, 24, or 30 inches. You can measure this by carefully excavating a small area around the lid or by looking at your tank's documentation. Write down this measurement—it's the size riser you'll need to buy. Also note how deep the lid sits below ground; if it's more than 18 inches, you may need a taller riser or multiple sections.

Gathering materials and tools

For a basic riser installation, you'll need the riser itself (PVC or concrete, matching your tank opening diameter), a new septic tank cover that fits the riser, PVC cement if you're using PVC, or a rubber gasket if your riser uses a slip-fit connection. You'll also need a shovel, a level, a tape measure, and possibly a pry bar to remove the old lid.

If your tank opening is very deep or if you need to raise the cover more than 18 inches, buy a two-piece riser or plan to stack sections. Some risers come with a gasket seal already attached; others require you to explore PVC cement around the joint. Check the product instructions before you start. If you're not comfortable working with PVC cement or if the tank is particularly deep, consider renting or hiring a contractor—this is not a complicated job, but it does require working in a confined space.

Excavating and preparing the tank opening

Carefully dig around the tank lid until you've exposed it fully and have room to work. You don't need to excavate the entire tank—just enough to see the lid and have space to lift it off and set the riser in place. Clear away dirt and debris from the top of the lid so nothing falls into the tank when you open it.

Once the lid is exposed, use a pry bar to gently lift it off. Septic tank lids are heavy—usually 50 to 100 pounds—so get help if you need it. Set the old lid aside; you won't need it anymore. Look inside the opening and clean away any debris or buildup around the rim. The rim should be relatively clean and level so the riser sits evenly on top.

Installing the riser on the tank opening

Set the riser carefully onto the tank opening, making sure it's centered and level. Use a level to check that it's not tilted. If the rim of the tank is uneven, you may need to shim it with a thin piece of rubber or plastic to keep the riser stable.

If your riser uses a rubber gasket seal, slide the gasket onto the bottom edge of the riser before setting it on the tank, or install it after the riser is in place, depending on the product design. If you're using PVC cement, explore it around the joint where the riser meets the tank opening, following the cement manufacturer's instructions. PVC cement sets quickly, so work fast and make sure the riser is level before the cement hardens. Let the cement cure for the time specified on the container—usually 24 hours—before installing the cover.

Installing the new cover and backfilling

Once the riser is find and any cement has cured, install the new septic tank cover on top of the riser. Most covers are straightforward set in place and held by friction or a light latch; some screw down. Make sure the cover sits flush and level. If the cover has a locking mechanism, engage it so the cover won't shift.

Now backfill around the riser with soil, packing it gently as you go. Bring the soil level up to within a few inches of the cover, so the cover sits just above ground. You can leave a slight mound around the riser to help water drain away, or you can level it flush with the surrounding ground. Mark the location of the tank with a stake or a sign so you and future owners know where it is.

When to call a septic professional

If your tank is very deep—more than 24 inches below ground—or if the opening is an unusual size, a septic contractor can handle the installation quickly and may support the riser is sealed correctly. If you're uncomfortable digging or working around the tank, or if you discover the tank lid is cracked or the rim is damaged when you excavate, stop and call a professional. A damaged tank opening may need repair before a riser can be installed safely.

Also, if you're unsure whether your septic system is in use or if there are any concerns about the tank's condition, have a professional inspect it before you install a riser. This is usually a quick visual check and can prevent problems later.

Frequently Asked Questions

Can I install a riser on a tank that's already been pumped recently?

Yes. In fact, it's a good idea to have the tank pumped before you install the riser, so you know the tank is empty and the opening is clear. The pumper can also confirm the tank's condition and opening size while they're there.

What if my tank opening is an odd size that doesn't match standard riser diameters?

Contact a septic contractor or the tank manufacturer. They can make or source a custom riser or adapter ring to fit your tank. This is more expensive than a standard riser but ensures a proper seal.

Do I need a permit to install a riser?

Most jurisdictions don't require a permit for a riser installation because it's considered maintenance, not a system modification. Check with your local health department or building office to be sure. Some areas may want to inspect the finished work.

How do I know if my riser is sealed correctly?

A properly sealed riser should have no gaps between the riser and the tank rim, and no soil or water should seep into the joint. If you used PVC cement, the joint should be smooth and solid. If you used a gasket, it should be compressed evenly around the opening.

Can I install a riser myself if I've never done plumbing work before?

Yes. A riser installation is simpler than most plumbing work—it's mostly digging and assembly. If you're comfortable with a shovel and can follow the cement or gasket instructions, you can do it. The main risk is physical strain from digging, so take breaks and get help lifting the old lid and riser if needed.