How to Install a Septic Tank Riser:
Step-by-Step Guide

Why Install a Riser:
The Case for Doing It Now

Septic tanks buried more than a few inches below grade require excavation every time they're pumped — adding $100–$200 per service visit and, more critically, creating enough friction that pump-outs get skipped. Skipped pump-outs let sludge overflow into the drain field, the leading cause of premature field failure. A field replacement costs $8,000–$30,000. A riser kit costs under $200.

Once installed, the pump-out crew reaches the tank in under five minutes with no digging. Baffle inspection takes seconds instead of a half-day of labor. The result is a system maintained on the schedule it was designed for — and one far less likely to produce an expensive surprise. Most polyethylene risers also accept a lockable lid, a safety requirement on any property with children or lawn equipment traffic.

Before You Start:
Tools and Materials

The Installation:
7 Steps

1. 1
   Locate and fully expose the tank lid

   If you don't have a record or diagram showing the lid's location, follow the outlet pipe from inside the house and probe outward — our guide to finding your septic tank covers this in detail before you start digging. Once you know where the lid is, excavate down to it, clearing enough soil to expose the full lid perimeter and at least 6 inches of the concrete collar around it. You need a clean, dry working surface for the sealant to bond properly.

   💡Most tanks have two lids — one over the inlet end (house side) and one over the outlet end (drain field side). Risers can be installed on one or both. Installing on the outlet end is most critical for pump-outs, since that's where the pump-out technician checks baffles.
2. 2
   Measure the burial depth and cut the riser to height

   With the lid fully exposed, measure from the top of the tank collar — where the riser base will seat — up to finished grade. This is your target riser height. Polyethylene riser sections come in standard heights (typically 6", 12", and 24"). Combine sections as needed to come close to grade, then mark and cut the top section to the precise remaining height using a utility knife scored around the circumference, or a handsaw for thicker-walled PVC.

   💡Stop 1–2 inches below finished grade — not flush. This protects the lid from direct mower contact and allows a clean soil or grass finish over the top without burying it again.
3. 3
   Clean the mating surfaces thoroughly

   Use rags to remove all soil, moisture, and debris from both the tank collar and the riser base. Sealant will not bond to dirty, damp, or dusty surfaces — this step directly determines how waterproof the finished joint is. If there is any existing adhesive residue from a prior riser installation, scrape it clean. Both surfaces need to be dry to the touch before sealant goes down.

4. 4
   Apply sealant and seat the riser base

   Run a continuous, unbroken bead of butyl rope sealant around the full perimeter of the tank collar. If your riser kit includes a pre-cut butyl tape ring instead, press it firmly into place along the full seating surface with no gaps. Lower the riser straight down onto the collar, aligning the base ring. Press firmly and check level — the riser must sit plumb, not tilted. Work around the base with the rubber mallet, tapping evenly to seat it fully. Wipe any sealant that squeezes out from the joint immediately with a rag.

   💡A tilted riser puts uneven stress on the sealant joint and can allow ground water infiltration into the tank. Take an extra minute with the level here — it's not correctable without reseating.
5. 5
   Stack additional sections if needed

   If burial depth requires more than one riser section, apply sealant to each intermediate joint the same way — full continuous bead, press, check level, mallet. Most polyethylene riser systems use a snap-and-gasket joint between sections; follow the manufacturer's seating instructions for each connection point. Do not skip sealant on intermediate joints: ground water pressure at depth will exploit any unsealed gap.

6. 6
   Attach the lid and install the safety lock

   Set the new lid on top of the riser and confirm it seats flat with no wobble around the edge. Install the safety lock hardware per the manufacturer's instructions — most designs require drilling one or more pilot holes into the riser collar and securing a stainless locking tab or hasp. Once installed, pull firmly on the lid to verify it cannot be lifted without the release tool. A lid that lifts freely is a hazard, not an access point.

7. 7
   Backfill and finish grade

   Backfill around the riser in layers, compacting each layer lightly before adding the next. Avoid dropping large soil chunks directly against the riser wall — compact gradually to prevent lateral stress on the sealant joint while it cures. Finish the grade so the top of the riser sits 1–2 inches below the surrounding lawn surface. Before the excavation evidence disappears, record the location: a landscape stake, a GPS coordinate, or a sketch in your home maintenance file. Future pump-outs start from that mark.

   💡Let the sealant cure for 24 hours before the first pump-out — most butyl products reach full bond strength overnight. Check the joint for any sign of shifting or lifting after backfill settles during the first heavy rain.

After Installation:
What to Expect

A properly installed polyethylene riser requires almost no maintenance. The material doesn't corrode, degrade in soil, or shift under normal ground movement. Check the lid and sealant joint visually every 2–3 years — look for any gap at the base, lid cracking, or uneven settling. Keep the rim clear of soil and grass overgrowth so the lid stays accessible.

A light mow over the lid is fine — most polyethylene lids are rated for lawn traffic. Do not drive heavy equipment over it. If the access point falls in a driveway or vehicle path, specify a traffic-rated lid when purchasing the kit; standard residential lids are not designed for vehicle load.

From this point, scheduling a pump-out every 3–5 years is all the system needs. The riser removed the main friction point — now the routine is simple enough to actually follow.

Frequently Asked Questions