What is Chemical Screen Blockage?

Understanding Chemical Screen Blockage in Water WellsBy Aquabiotics Industrial – Experts in Bore Maintenance and Rehabilitation

What is Chemical Screen Blockage?

Chemical screen blockage is a common but often misunderstood cause of reduced water production in bores and wells. Unlike physical blockages (like sand and silt) or biological blockages (caused by bacteria), chemical blockage results from the precipitation and build-up of mineral scales on and around the well screen.

Over time, these minerals—primarily calcium and magnesium carbonates or sulfates—form hard crusts on the inside of the screen and cement the gravel pack and aquifer material on the outside. This reduces water flow into the well, impacts pump efficiency, and ultimately shortens the lifespan of the well.

Why Does it Happen?

Mineral scale forms when water chemistry and flow conditions combine in the right (or rather, wrong) way:

• Water velocity increases and pressure drops at the entrance of the well screen.

• These conditions cause dissolved minerals in the groundwater to precipitate (fall out of solution) and deposit on the metal surfaces of the well.

• These are the same white crusty minerals you might see around taps and showerheads—just much harder to deal with underground.

The Role of Water Velocity

One of the key design considerations for a well is entrance velocity—how fast water moves through the screen slots.

• A well-designed screen should keep entrance velocity below 0.1 feet per second.

• If water enters too quickly, it accelerates mineral precipitation.

• As blockages start forming, water is forced through fewer openings, increasing the velocity further and creating a feedback loop of worsening incrustation.

Cementing the Gravel Pack

Chemical blockage doesn’t just affect the screen itself. Over time, minerals bind the surrounding aquifer materials and gravel pack into a solid mass. This creates a hardened "shell" around the screen, making redevelopment more difficult and less effective if left too long.

Chemical vs Biological: Know the Difference

It’s important to distinguish between chemical incrustation and biological blockage:

• Chemical scale is made of minerals.

• Biological blockage (e.g., from iron-reducing bacteria) involves organic materials and biofilms.

• They often occur together, but each requires a different treatment approach. Misidentifying the cause can waste time, money, and further damage the well.

Preventing and Treating Chemical Blockage

Preventative design and regular maintenance are key.

• Design for low entrance velocity to reduce initial scale formation.

• Monitor water quality regularly, especially for hardness and pH.

• Schedule redevelopment periodically to remove early-stage buildup before it hardens.

• Use specialised acid treatments to dissolve carbonate and sulfate scales (best done by professionals with experience in bore maintenance).

Final Thought

Chemical blockage can quietly strangle a bore’s performance. Left untreated, it turns a once-productive well into an underperforming or even unusable asset. Early identification and regular rehabilitation can save thousands in drilling costs and extend the life of your infrastructure.

Need help diagnosing or treating chemical blockage in your bore?Contact Aquabiotics Industrial – Australia's experts in bore cleaning and well rehabilitation.🌐 www.aquabiotics.com.auLet’s get your bore flowing again.