PVC Well Casing vs. Screen vs. Filter Pipe: Choose Wisely

Core Selection Principle: Pipe Function Must Match Subsurface Conditions

The selection of PVC well pipe is not determined by material properties alone—it is dictated by compatibility between the pipe's intended function and the specific subsurface conditions encountered. The critical judgment is: does this pipe type address the geological formation, water chemistry, and operational demands of this specific well? Selection errors stem from choosing pipe based on general categories rather than scenario requirements.

What Each Pipe Type Actually Does (Functional Definition)

Solid PVC Well Casing: Structural Integrity and Aquifer Isolation

Solid PVC casing serves as the wellbore's structural backbone. Its function is to:

• Prevent wellbore collapse in unstable formations
• Isolate aquifers from surface contamination
• Provide a conduit for drilling and pump installation

When it is the right choice: Competent rock formations, stable subsurface conditions, or wells where water inflow will be controlled by a separate screen assembly installed within or below the casing.

When it is not sufficient: Formations requiring controlled water entry directly through the pipe wall (granular aquifers, sand-bearing zones).

PVC Screen Pipe: Controlled Water Entry with Sediment Exclusion

Screen pipes feature engineered slots or perforations designed to allow selective water inflow while excluding formation particles. The slot size is matched to formation grain size.

Core function: Enable water entry while preventing sand and larger sediment from entering the wellbore, protecting pump equipment and maintaining well efficiency.

Not the same as: Filter pipes, which provide finer filtration; or solid casing, which blocks all inflow.

PVC Filter Pipe: Precision Filtration for Challenging Formations

Filter pipes employ finer mesh, specialized construction, or gravel pack interfaces to achieve higher filtration precision than standard screens.

When specialized filtration is necessary: Very fine sands, silts, aquifers with poor natural filtration, or applications requiring high water clarity for pump protection or end-use quality.

Four Subsurface Factors That Dictate Pipe Selection

Factor 1: Geological Formation Characteristics

The judgment: Particle size and formation stability determine whether you need structural support only (casing), controlled inflow (screen), or precision filtration (filter pipe).

• Solid rock or competent formations → Solid casing provides structural support; water entry managed separately
• Sand, fine gravel, granular aquifers → Slotted screen pipe; slot width matched to grain size distribution
• Very fine sand, silt, unstable formations → Specialized filter pipe to prevent fine particle migration

Why this matters: Improper screen slot sizing causes either sand pumping (slots too wide) or aquifer destabilization from excessive drawdown (slots too narrow).

Factor 2: Water Chemistry and Material Longevity

The judgment: Acidity, salinity, and dissolved mineral content determine long-term pipe integrity and whether chemical degradation will limit well lifespan.

• Acidic or alkaline water affects PVC's chemical resistance limits
• High salinity influences corrosion potential and material interaction
• Dissolved minerals (calcium, iron, manganese) cause scaling that can clog screen slots or reduce flow capacity

Proactive consideration required: Even PVC, while generally resistant, has chemical limits. Understanding water chemistry allows prediction of material performance over the well's operational life.

Factor 3: Pumping Rates and Operational Pressure Demands

The judgment: High pumping rates impose structural loads and flow capacity requirements that affect both pipe strength and screen open area.

• Low-volume domestic wells → Lower structural demands; standard pipe specifications often sufficient
• High-volume irrigation or industrial wells → Pipes must withstand higher pressures; screens require adequate open area to prevent excessive drawdown that destabilizes formations

Critical distinction: Operational pressure is not just about pipe strength—it directly affects formation stability through the screen. Excessive drawdown from insufficient screen area can cause aquifer collapse or sand migration.

Factor 4: Required Water Quality Post-Filtration

The judgment: End-use purity requirements dictate the necessary filtration precision.

• Potable water from fine-grained aquifers → May require filter pipe to achieve clarity standards
• Industrial or irrigation use with sediment tolerance → Standard screen pipe typically sufficient
• Pump protection in silt-prone formations → Enhanced filtration prevents premature pump wear