Understanding Holding Tank Installation: What Happens After We Leave

Installing a holding tank is a critical step in managing your home’s wastewater. But, it’s

important to understand that the job isn’t truly “finished” the day the tank is set.

One of the most common misunderstandings we see is around what the site will look

like after installation, and what needs to happen next.

Rough Grade vs. Final Grade

At the completion of a holding tank installation, the area is brought back to rough

grade, not final grade.

This means:

•  The excavation is backfilled properly

•  The tank is set and secured

•  The ground is leveled as best as possible for initial completion

However, the soil around and above the tank has been recently disturbed. Because of

this, it will naturally settle over time.

Why Settling Happens

Even when backfilled correctly, soil will continue to settle due to:

•  Rainfall

•  Ground moisture changes

•  Seasonal freeze and thaw cycles

•  Natural consolidation of disturbed soil

This settling is completely normal, but it will result in low spots and uneven ground

above the tank.

The Homeowner’s Responsibility

After installation, it is the property owner’s responsibility to bring the area to final

grade.

This typically involves:

•  Adding additional fill as the ground settles

•  Smoothing and leveling the area

•  Establishing proper drainage away from the tank and risers

•  Completing final landscaping (topsoil, seed, sod, etc.)

  
  

This step is not cosmetic—it is essential to the long-term performance of your system.

The Importance of Proper Grading

Final grading plays a major role in protecting your holding tank.

If the area is not properly graded:

•  Water can pool above the tank

•  Excess moisture can work its way around risers and lids

•  Freeze/thaw cycles can become more aggressive in saturated soil

To prevent this, the ground should always be shaped so that water sheds away from

the tank and risers, not toward them.

Groundwater, Frost, and Spring Conditions

It is common to see some groundwater enter a holding tank, especially during the

first spring after installation.

This can happen because:

•  Frost lifts and shifts the soil during winter

•  That movement can slightly separate or disturb the risers

•  When snow melts and the ground becomes saturated, water can temporarily work its way into the tank at those points

There is no practical way for the installer to fully prevent this, as it is directly related

to natural frost movement and site conditions, not improper installation.

As temperatures warm and frost leaves the ground:

•  The soil begins to settle back into place

•  Risers typically resettle

•  Sealant joints can tighten back up and re-seal at the seams

Because of this temporary condition, it is not unusual for homeowners to require an

additional pumping in the spring.

Proper final grading and landscaping—especially directing water away from the

risers—will significantly reduce the likelihood of this happening in future seasons.

Setting Realistic Expectations

A holding tank installation should be viewed in two phases:

Phase 1: Installation (Contractor Scope)

•  Tank placement

•  Connections

•  Backfilling

•  Rough grading

Phase 2: Final Grading & Landscaping (Property Owner Responsibility)

•  Adding fill as needed

•  Establishing final grade

•  Managing drainage

•  Completing landscaping

Understanding this upfront helps avoid confusion and ensures your system performs as

intended.

Final Thoughts

A properly installed holding tank is only part of the equation. What happens after installation, especially proper grading, drainage, and seasonal ground movement, has a direct impact on how well your holding tank system performs over time.

Taking the time to bring the area to final grade and ensure proper water runoff will help prevent common holding tank issues, reduce maintenance needs, and protect your investment. For homeowners in Central Wisconsin, where freeze and thaw cycles and spring groundwater are common, proper grading and drainage are especially important to keep your system working as it should.

When everything is finished correctly, you’ll extend the life of your holding tank system and avoid unnecessary problems down the road. If you’re planning a holding tank installation in Gleason, Merrill, Tomahawk, Rhinelander, or Antigo, working with us here at Young's Plumbing can make all the difference in protecting your property and keeping your system running smoothly.