Introduction

Many homeowners experience the same cycle: the septic tank and soakaway are pumped, everything works fine for a short time, and then the system fills up again. This frustrating problem often leads people to believe that their septic tank is too small or faulty.

The truth is, if your soakaway and septic tank keep filling quickly after pump-out, the issue usually lies in soakaway failure, poor soil drainage, or improper system design. Pumping only provides temporary relief. Let’s look at the major causes and what you can do to fix them permanently.

Causes of Septic Tank and Soakaway Refilling After Pumping

1. Soakaway Failure (Clogged Soil)

Over time, soap scum, grease, and suspended solids from wastewater clog the soil pores around the soakaway.

Once this happens, the soakaway can no longer absorb liquid, and it behaves like a sealed tank that fills up quickly.

2. High Water Table or Poor Soil Percolation

In areas with clay soil or high groundwater levels, effluent has nowhere to drain.

Even after pumping, water seeps back in or stagnates, causing the system to refill within days or weeks.

3. Improper Soakaway Construction

Many soak pits are built like storage tanks instead of percolation pits.

Without honeycomb block walls, perforated rings, or gravel bases, they cannot allow liquid to infiltrate into the ground.

4. Sludge Migration Into Soakaway

A septic tank should have baffle walls to separate solids from liquids.

If these are missing or damaged, sludge flows directly into the soakaway, clogging it permanently.

5. Excessive Water Load

When roof gutters, laundry, or kitchen wastewater are connected to the septic system, the volume overwhelms both the tank and soakaway.

As a result, the soakaway fills up faster than it was designed to handle.

6. Collapsed or Blocked Soakaway

With age, soakaway walls can collapse or tree roots may invade, blocking infiltration.

Instead of draining, the soakaway simply stores liquid until it overflows back into the septic system.

Solutions to Stop Septic and Soakaway from Filling Too Quickly

Short-Term Fixes

Pump out the system to relieve pressure (temporary solution).

Redirect roof water and surface runoff away from the soakaway.

Install a grease trap before the septic tank to prevent fats and oils from reaching the soakaway.

Medium-Term Measures

1. Separate Greywater and Blackwater

Send laundry and kitchen wastewater into a separate soak pit.

Keep toilet sewage for the septic tank and soakaway only.

2. Routine Maintenance

Desludge the septic tank every 2–5 years, depending on usage.

Regular checks help prevent solids from reaching and blocking the soakaway.

Medium-Term Measures

1. Separate Greywater and Blackwater

Send laundry and kitchen wastewater into a separate soak pit.

Keep toilet sewage for the septic tank and soakaway only.

2. Routine Maintenance

Desludge the septic tank every 2–5 years, depending on usage.

Regular checks help prevent solids from reaching and blocking the soakaway.

Permanent Long-Term Solutions

1. Rebuild the Soakaway Properly

Use honeycomb block walls or perforated concrete rings.

Add gravel at the base for better drainage.

Site the soakaway away from groundwater or flood-prone areas.

2. Upgrade to a Biodigester System

Biodigesters treat waste biologically, breaking down solids into water and gas.

They require little to no soakaway, work in all soil types, and need minimal desludging.

3. Professional Soil Test Before Construction

A percolation test helps determine the right soakaway size and location.

This ensures the design matches the soil’s drainage capacity.

Conclusion

If your septic tank and soakaway keep filling up shortly after pumping, the real issue is not the septic tank itself, it’s usually a failed soakaway, poor drainage soil, or bad system design. Pumping gives only temporary relief.

For a lasting solution, consider rebuilding the soakaway with proper materials, reducing water load, or investing in a modern biodigester system. These steps may cost more upfront, but they save you years of constant pumping, foul smells, and costly repairs.