Your Drainfield Has a Secret Layer — And It Might Be the Problem

You’ve pumped your tank. You’re careful about what goes down the drain. So why are you still dealing with backups or pooling water?

The answer may be something you’ve never seen — but your system knows it’s there: biomat.

What Is Biomat?

Biomat is a dense, jelly-like layer made up of bacteria, organic waste, and residual material. It forms beneath drainfield pipes, where wastewater leaves the tank and enters the soil.

At first, biomat is helpful. It acts as a natural filter, breaking down waste and protecting groundwater.

Over time — especially in older or stressed systems — biomat can thicken. When it becomes too dense, water can no longer pass through it efficiently. That’s when problems begin.

Common Causes of Biomat Overgrowth

• Aging systems: After 15–25 years, soil compaction and biological buildup are common

• Chemical cleaners: Bleach and antibacterial products weaken beneficial bacteria

• Excess water: Long showers, frequent laundry, or heavy rainfall overload the system

• Weak biology: Poor bacterial activity allows more organic material to reach the drainfield

Signs Your Biomat May Be Restricting Flow

• Water pooling over the drainfield

• Slow drains or gurgling toilets

• Persistent odors, even after pumping

• Backups during or after storms

If you’ve already pumped your tank and issues continue, the tank is usually not the problem — the drainfield is.

What Pumping Won’t Fix

Pumping removes accumulated solids from inside the tank.

But biomat forms in the soil outside the tank — so pumping alone does not address it.

This is why many homeowners see symptoms return shortly after a pump-out: the underlying hydraulic restriction remains.

How Biologic™ SR2 Septic Helps

Biologic™ SR2 Septic does not add foreign enzymes or laboratory-grown bacteria. Instead, it supports the native bacteria already present in your system by supplying plant-based micronutrients.

This biological support can help:

• Improve waste breakdown before it reaches the drainfield

• Reduce organic buildup contributing to biomat thickening

• Lower sludge and odor levels in the tank

• Supports system health and drainfield flow

Biologic™ SR2 Septic is trusted in industrial and municipal wastewater systems worldwide — and is now available for residential septic systems.

What If It’s Too Late?

If your system has structural damage — such as crushed pipes or severe root intrusion — no biological treatment can correct that.

But before committing to a $10,000+ drainfield replacement, many homeowners choose to support and restore system biology. In many cases, improved biological performance helps relieve symptoms and extend system life.

Final Thoughts

Biomat isn’t the enemy — excessive biomat is.

If your system is 15+ years old, sluggish, or backing up even after pumping, don’t ignore it. The sooner you address biological imbalance and hydraulic stress, the better your chances of recovery.

Don’t just pump. Restore.

For a plain-language explanation of how septic systems work as a whole — including why drainfields fail and what responsible care looks like — see the SeptiCorp Manifesto.