Fiberglass vs Precast Concrete: Which Is the Better Choice for MIC-Sensitive Wet Wells?

Bren McNeely
Jun 12
2 min read

Updated: Jul 1

When it comes to building long-lasting wet wells and lift stations, many municipalities default to fiberglass for one reason: resistance to MIC (Microbial-Induced Corrosion). But corrosion isn’t the only factor that matters in underground infrastructure.

If you’re comparing fiberglass vs precast concrete, it’s important to take a closer look at what each material truly offers. Pay special attention to strength, longevity, and long-term performance in the field.

Fiberglass vs precast concrete lift station side by side

MIC Protection: It’s Not Just a Fiberglass Advantage

Yes, fiberglass resists MIC. Modern precast concrete does too, when it's manufactured with the right protective elements.

MIC-protected concrete structures possess these two components:

Anti-microbial admixtures to prevent the bacteria that cause MIC
Factory-applied, acid-resistant coatings for added protection against hydrogen sulfide gas

These upgrades allow precast concrete to perform just as well as fiberglass in corrosive environments, while also solving the structural and installation issues that fiberglass creates. PS: Gainey's concrete products include these components.

Fiberglass Limitations: What’s Not in the Spec Sheet

When evaluating fiberglass vs precast concrete, it's important to look beyond corrosion:

Difficult to install at deep depths: One-piece fiberglass wells are harder to handle and set
Structurally vulnerable during backfill, especially in large diameters
Not traffic-rated unless reinforced, which adds complexity and cost
Lightweight material leads to flotation risk without heavy anchoring
UV and impact degradation over time can shorten its effective lifespan

While fiberglass may check the MIC box, it often falls short in the categories that matter just as much, especially on public projects with long service expectations.

Why Precast Concrete Is the Better Long-Term Choice

Let’s break it down:

Category	Fiberglass	Precast Concrete
MIC Resistance	✅ Yes	✅ Yes (admixtures + coatings)
Structural Strength	❌ Limited	✅ Built for depth & traffic loads
Floatation Risk	❌ High (lightweight)	✅ Low (heavy, self-anchoring)
Traffic Rating	❌ Not standard	✅ Standard precast option
Backfill Durability	❌ Easily damaged	✅ Stable and load bearing
Lifespan	⚠️ 30–50 years	✅ 50–100+ years
Environmental Impact	❌ Petroleum-based	✅ Natural, recyclable materials

Precast concrete doesn’t just match fiberglass on corrosion resistance; it exceeds it in every other key area.

Contact us about Fiberglass vs Precast Concrete

If you're still specifying fiberglass to combat MIC, it's worth reevaluating. Precast concrete, when manufactured with microbial-resistant technology, gives you: