Water Well Screens
Water well screens are also known as wedge wire screens, well screens, wire wrapped well screens, v shaped water well screens.
Water Well Screens — Continuous Slot, Wedge Wire Wrapped
Water well screens are manufactured by wrapping a V-shaped (wedge-shaped) profile wire around an internal array of longitudinal support rods. At every intersecting point the wire is fusion-welded to the rod, so the screen becomes a rigid structural pipe rather than a mesh layer on a pipe. Because the wire wraps continuously over the full length of the screen, the openings form one uninterrupted slot — the continuous slot — which lets water enter the well freely and in ample quantity while keeping the majority of sand and gravel out of the borehole.
In this guide you will find how the screen works, full size and slot specifications, how to choose a slot size for a given formation, material and end-connection options, and the quality tests each screen passes before it leaves our factory in Xinxiang, China.
Quick specifications — Diameter 25–1200 mm | Slot 0.10–3.0 mm (custom) | Section length up to 6 m | Open area up to 60% | 304 / 316L stainless steel, carbon steel | Threaded, flanged or welded connections
What Are Water Well Screens?
A water well screen is the intake section at the bottom of a well. Casing carries water up the hole; the screen is the part that is set opposite the water-bearing formation, and it has to do two jobs at once: hold back the formation material (sand, gravel, fines) and let water pass with as little resistance as possible. Every design decision on a well screen — slot width, wire profile, open area, rod count, material grade — is a trade-off between those two jobs.
The type described on this page is the continuous slot wire-wrapped screen. It is known by several names that all refer to the same construction:
- Water well screen, well screen, water well strainer
- Wedge wire screen, V-wire screen, Vee-wire screen
- Johnson screen, Johnson well screen, Johnson-type screen tube
- Wire-wrapped screen, continuous slot screen, all-welded well screen
Water well screens and “Johnson screen”
“Johnson screen” is a brand name that became the generic term for this construction, in the same way a brand name becomes the everyday word for a product category. What defines the category is not the name but three engineering features: a V-shaped profile wire, a continuous slot formed by wrapping that wire spirally over longitudinal rods, and welding at every wire-to-rod intersection so the assembly is self-supporting.
Any manufacturer producing that construction makes a Johnson-type screen. Oasis has manufactured wedge wire well screens since 2003, exports them to more than 30 countries, and supplies them as both standard catalogue sizes and fully customised screen assemblies with casing, centralisers and shoe. If your tender documents say “Johnson screen”, “continuous slot screen” or “V-wire well screen”, this is the product they mean.
How it compares with other intake types
| Intake type | Typical open area | Sand control | Main limitation |
|---|---|---|---|
| Continuous slot wire-wrapped | 20–40% typical, up to 60% | Precise: uniform slot held to ±0.05 mm | Higher unit cost than slotted pipe |
| Slotted pipe (saw-cut) | 5–12% | Slot width varies along the joint | Low open area, high entrance velocity |
| Bridge slotted screen | 10–20% | Good for gravel packs | Slots not continuous; weaker in fine sand |
| Perforated pipe | 5–15% | Poor — holes admit sand | Only suitable with a gravel pack |
| PVC slotted screen | 5–15% | Limited | Low collapse strength, shallow wells only |
Open area figures are typical ranges; confirm against the actual slot width and diameter for your design.
Five advantages that matter in operation
- Continuous slot resists plugging. The V-shaped section produces a slot that opens outward through the wire thickness, so particles that enter the mouth fall through instead of wedging against the wire. Flow stays unobstructed and cleaning is easier.
- Higher open area means lower entrance velocity. With more open area, the same yield passes through the slot at lower velocity, so fines are less likely to be dragged into the screen under drawdown. That improves sand control, raises specific capacity and extends well life.
- All-welded construction. Wire and support rods are welded at every contact point, not glued, wrapped or clipped. The screen is a load-bearing structure that can be handled, run and, where needed, pulled.
- Better collapse resistance. Longitudinal support rods plus the welded wire cage carry external formation and hydrostatic pressure, which matters in deep wells and in unconsolidated formations.
- Fully customisable. Diameter, slot, rod count, wire profile, material and end connection are specified to your well design. Non-standard sizes are routine, not an exception.
How They Work: the V-Wire and the Continuous Slot
Four components make up the screen, and each one has a job:
Profile wire (V-wire) — the filtration surface. A triangular-section wire with a narrow face on the outside and a wide base on the inside; this is what creates the slot.
Longitudinal support rods — the load path. Spaced around the circumference, they carry axial load and resist collapse, and the wire is welded to them.
End rings and fittings — transfer load to casing and provide the connection: threaded coupling, flange, welding ring or bevel.
Internal liner (optional) — a perforated tube added inside the screen when the design needs extra compressive strength; its purpose is structural, not filtration.
Why the wire is V-shaped
The slot is measured across the narrow outer face of the wire. Moving inward through the wire, the gap widens.
Diagram 1 — V-shaped wire cross-section. The slot is accurate at the outer face and opens up behind it.
That geometry has three practical consequences:
- No wedging. A grain that reaches the mouth either passes through or stays outside; it cannot jam half-in as it does in a parallel-sided saw cut.
- Only two lines of contact. The wire touches the sand at its narrow outer edge, so there is very little surface for encrustation and bacterial growth to grip.
- Self-cleaning. During development and backwash, flow reverses easily because the opening grows toward the inside.
How the continuous slot is made
Support rods are laid parallel along the axis and spaced by a jig. The profile wire is then wound helically around them under tension, and at each intersection it is resistance-welded to the rod. Two things follow from winding rather than cutting slots:
- The slot is one continuous opening from one end of the screen to the other, with no land or bridge interrupting it. The full circumference and full length are available as intake area.
- The pitch sets the slot. Slot width is controlled by wire pitch to a tolerance of about ±0.05 mm, so every opening along a 6 m section matches the design value. This is the property that makes tight sand control repeatable from well to well.
Diagram 2 — From rod cage to continuous slot screen.
During construction the screen sits opposite the target formation, usually with a gravel pack around it, and the well is developed until the water runs clear. During production the pumps draw water through the slot at a controlled entrance velocity. The screen's resistance is what keeps that velocity below the level that would mobilise the formation. A well screen that is correctly sized — right slot, right open area — will produce sand-free water at design yield. One that is undersized in open area will not, no matter how good the wire is.
Specifications
The tables below cover what we hold to as standard. Anything outside them can be manufactured to drawing — state the diameter, slot, material and end connection, and we will quote against your well design.
Standard screen sizes
| Nominal size | Outer diameter | Inner diameter | Slot range | Sections per well |
|---|---|---|---|---|
| 2″ | 60.3 mm | 51 mm | 0.10–1.0 mm | 1 m / 3 m |
| 3″ | 88.9 mm | 78 mm | 0.10–1.5 mm | 1 m / 3 m |
| 4″ | 114 mm | 101.6 mm | 0.10–2.0 mm | 3 m / 6 m |
| 5″ | 141 mm | 128 mm | 0.15–2.0 mm | 3 m / 6 m |
| 6″ | 168 mm | 152.4 mm | 0.15–2.5 mm | 3 m / 6 m |
| 8″ | 219 mm | 203.2 mm | 0.20–3.0 mm | 3 m / 6 m |
| 10″ | 273 mm | 254 mm | 0.20–3.0 mm | 3 m / 6 m |
| 12″ | 325 mm | 304.8 mm | 0.30–3.0 mm | 3 m / 6 m |
| 14″ | 377 mm | 355.6 mm | 0.30–3.0 mm | 3 m / 6 m |
| 16″ | 426 mm | 406 mm | 0.50–3.0 mm | 3 m / 6 m |
| 20″ | 508 mm | 483 mm | 0.50–3.0 mm | 3 m / 6 m |
| 24″ | 630 mm | 600 mm | 0.50–3.0 mm | 3 m / 6 m |
| 30″–48″ | 762–1200 mm | to drawing | 0.50–3.0 mm | to drawing |
Custom diameters from 25 mm to 1200 mm. Inner diameter depends on wire height and rod size; the values above are typical for the standard build.
Profile wire options
| Wire code | Head width | Height | Side angle | Typical use |
|---|---|---|---|---|
| 47 | 1.19 mm | 2.24 mm | 13° | Small diameter wells, monitoring |
| 60M | 1.52 mm | 2.54 mm | 13° | 4″–6″ water wells |
| 69M | 1.80 mm | 4.30 mm | 8° | General purpose, good open area |
| 85D | 2.20 mm | 5.10 mm | 8° | 8″–12″ production wells |
| 90M | 2.29 mm | 3.56 mm | 13° | Fine sand formations |
| 100D | 2.54 mm | 5.90 mm | 5° | High open area, coarse sand |
| 118 | 2.90 mm | 4.70 mm | 13° | Large diameter municipal wells |
| 120M | 3.05 mm | 6.60 mm | 3° | Heavy duty, deep wells |
| 122 | 3.10 mm | 6.00 mm | 9° | Deep wells, high collapse demand |
| 150D | 3.80 mm | 9.00 mm | 9° | Gravel pack, large slot |
| 160 | 4.14 mm | 6.35 mm | 9° | Very coarse formations, dewatering |
Side angle is the taper of the wire flank — a smaller angle gives a faster-opening slot. Wire height sets mechanical strength: taller wire, stronger cage, lower open area at the same slot.
Open area by slot and diameter
| Slot | 4″ (114 mm) | 8″ (219 mm) | 12″ (325 mm) | 24″ (630 mm) |
|---|---|---|---|---|
| 0.25 mm | 8–10% | 8–10% | 8–10% | 8–10% |
| 0.50 mm | 15–18% | 15–18% | 15–18% | 15–18% |
| 1.00 mm | 24–28% | 25–29% | 25–29% | 25–29% |
| 1.50 mm | 30–34% | 32–36% | 32–36% | 32–36% |
| 2.00 mm | — | 37–41% | 38–42% | 38–42% |
| 3.00 mm | — | — | 44–48% | 44–48% |
Indicative only — open area depends on wire head width and rod diameter, so confirm the figure for your specific build before using it in an entrance-velocity calculation.
Tolerances and general data
| Slot tolerance | ±0.05 mm on slot widths up to 1.0 mm; ±0.10 mm above 1.0 mm |
| Diameter tolerance | ±1.5 mm |
| Length tolerance | ±5 mm per section |
| Straightness | ≤1.5 mm per metre |
| Standard lengths | 1 m, 3 m, 6 m (cut to order) |
| Slot size range | 0.10 mm – 3.0 mm |
| Surface finish | Pickled and passivated, polished, or mill finish |
| Design depth | Up to 300 m standard; deeper on engineered design |
Slot Size Selection by Formation
Slot size is the single decision that most affects whether a well produces clear water and lasts. Two rules govern it:
- Without a gravel pack, the slot must be fine enough to retain the formation itself. The standard approach is to sieve a representative formation sample and set the slot to pass 40–50% of the sample by weight — the d40 to d50 range.
- With a gravel pack, the pack does the retaining and the screen only has to hold the pack. Here the slot is set from the pack gradation, typically 2 to 3 times finer than the pack's d50, and the slot can be considerably larger — which is how gravel-packed wells get both high open area and good sand control.
The table below is a starting point for design discussions. It is not a substitute for a sieve analysis of your actual formation — send us a sample and we will recommend a slot with the calculation shown.
| Formation | Typical slot | Gravel pack | Notes |
|---|---|---|---|
|
Fine sand / silt d50 < 0.15 mm |
0.10–0.20 mm | Strongly recommended | Very small slots are slow to develop; a pack stabilises the formation and allows a more practical slot |
|
Fine sand d50 0.15–0.25 mm |
0.15–0.25 mm | Recommended | The classic Johnson application; check entrance velocity against open area |
|
Medium sand d50 0.25–0.50 mm |
0.25–0.50 mm | Optional | Widest slot range that still gives reliable sand control without a pack |
|
Coarse sand d50 0.50–1.0 mm |
0.50–1.0 mm | Rarely needed | Good open area; a formation stabiliser or pack may still be specified |
|
Fine gravel d50 1.0–2.0 mm |
1.0–2.0 mm | No | High open area; confirm collapse strength for the setting depth |
|
Gravel / boulders d50 > 2.0 mm |
2.0–3.0 mm | No | Fractured rock and coarse alluvium; the screen mainly protects against rubble, not sand |
| Consolidated sandstone / limestone | 0.50–1.5 mm | No | Slot set to retain any loose interbeds rather than the rock itself |
| Gravel pack design | 2–3× finer than pack d50 | Design element | Pack gradation selected first, then the screen slot sized to retain it |
Slot ranges are practical starting points for typical hydrogeological conditions. Final selection should follow a sieve analysis of the formation and, for gravel packs, of the pack material.
Three checks before you fix the slot
- Sample depth matters. A composite sample that mixes a clay band with clean sand will give you the wrong d50. Ask for a sample from the screen interval only.
- Check entrance velocity. Divide design yield by the total open area. If the result is above roughly 0.03 m/s, fines will be mobilised — enlarge the screen, add length, or widen the slot with a pack.
- Do not over-tighten. Going finer than the formation requires buys nothing and costs open area, well development time and pump efficiency. It is a very common design error.
Materials & End Connections
Wire and rod material
| Material | Best for | Watch out for |
|---|---|---|
| SS 304 | Potable water, irrigation, clean groundwater, moderate chloride | Not for brackish or high-chloride water; general corrosion risk |
| SS 316 / 316L | Slightly aggressive groundwater, coastal sites, municipal supply, sensitive water chemistry | Higher cost; still not immune to chlorides above about 500 mg/L |
| Duplex 2205 | Brackish water, higher chloride, geothermal, seawater-adjacent | Longer lead time; specify it early in the project |
| Carbon steel (galvanised or coated) | Shallow wells, temporary dewatering, cost-driven projects | Corrosion limits life; not recommended for potable supply long term |
For drinking water projects, state the required certification in your enquiry — material traceability documentation (mill certificates) can be supplied with the order.
End connections
- Threaded ends — API or metric threads with couplings. The usual choice for small to medium diameter wells and for stacked sections; fast to make up and reliable.
- Flanged ends — bolted flanges for large diameters, high axial loads and applications where the screen may be removed. Gives a positive, gasketed joint.
- Welded ring / bevel ends — a prepared ring or bevel for field welding to casing. Common on large diameter municipal and industrial wells.
- Spline / flush joint — flush outside profile so the assembly passes a gravel pack without snagging.
- Bottom cap, shoe and centralisers — supplied with the screen where the design requires a closed bottom, a driving shoe, or centralisation in the borehole.
Related components on our site: pipe-based well screens, gravel pack screens, bridge slotted well screens, sand control screens and centralisers.
Applications
The construction is the same across applications; what changes is the slot, the material and the connection detail. The four below account for most of what we ship.
Drinking water wells
Municipal and rural supply wells. Specification is driven by water quality and by the need for sand-free water without a maintenance burden. SS 304 or 316L with a pickled and passivated finish, slots set from sieve analysis, and full material traceability. Where the aquifer is fine sand, a gravel pack is standard.
Ground source heat pump (GSHP) wells
Thermal response and standing-column wells for closed and open loop systems. The screen must resist the thermal cycling and the chemistry of the return water, and it must not shed fines into the loop, so slot selection and pack design are as important as in a supply well. 316L is usual.
Agricultural irrigation wells
High-volume, seasonal duty. Wide slots and a coarse pack give the open area needed for large yields, and the screen has to tolerate repeated start-stop pumping and, in many regions, aggressive groundwater. SS 304 with a heavy-duty wire profile is the cost-effective choice; duplex where chloride is high.
Mine dewatering and depressurisation
Deep wells drilled to lower the water table around a pit or shaft, often in fractured rock or mixed formations. Depth drives the requirement: higher collapse strength, heavier wire, more rods, flanged or welded connections rather than threads. Dewatering wells are frequently pulled and reinstalled, so the welded cage is a real advantage.
Outside water wells, the same wedge wire construction is used for oil and gas sand control, mineral processing screens, and filtration of liquid and powder in the chemical, fertiliser, salt, grain and pharmaceutical industries — see wedge wire screen and industry filters.
Case Studies
Two projects that show how the specification is set in practice.
Drinking Water Project in Sudan
A potable water programme delivered through a local distributor. We signed a well screen agency agreement with the distributor and supplied continuous slot screens for the well fields, so that specification and after-sales support were handled locally rather than at a distance. Read the Sudan case →
Deep Water Well Drilling Project in Morocco
A deep well programme in which the screen was only one part of the order: stainless steel casing, water well screen, drill bit and API casing were supplied together. Packing the well completion from a single source kept the diameter stack and the connection details consistent. Read the Morocco case →
More field reports are on the case studies page.
Quality & Testing
Every screen is inspected before packing. The inspection points that matter most to a well owner are these:
| Test | What it proves | How it is done |
|---|---|---|
| Slot gauge check | Slot width is within tolerance along the full length | Go/no-go gauges and measurement at intervals; 100% of sections |
| Collapse test | The cage resists external pressure at the design setting depth | Hydraulic external pressure on sample sections to a defined test pressure |
| Tensile / pull test | The welded joint carries the hanging weight of the screen string | Axial load applied to a section; weld and connection inspected afterwards |
| Weld inspection | Every wire-to-rod intersection is fused, no missed points | Visual inspection of all intersections plus tap test; destructive check on coupons |
| Dimensional check | Diameter, length, straightness and connection match the drawing | Measured against drawing; thread gauges on threaded ends |
| Surface and material check | Correct grade, clean surface, no free iron contamination | Mill certificates; pickling and passivation of welds; visual inspection |
Orders can be witnessed by a third-party inspector, and an inspection report with photographs is issued before shipment on request. Our quality system is certified to ISO 9001, with ISO 14001 and ISO 45001 also held; see quality guarantee and certificates.
Frequently Asked Questions
What slot size do I need for my well?
Without a gravel pack, the slot should retain the formation: as a rule, the slot passes 40–50% of a representative formation sample by weight. With a gravel pack, size the slot to retain the pack (about 2–3 times finer than the pack d50). Send us a sieve analysis and we will recommend a slot and show the calculation.
What is the difference between a Johnson screen and a wedge wire screen?
None in construction. “Johnson screen” is a brand name that became the generic term for a screen made from V-shaped profile wire wound continuously around longitudinal support rods and welded at every intersection. “Wedge wire screen”, “V-wire screen”, “continuous slot screen” and “wire-wrapped screen” all describe the same product.
304 or 316L stainless steel?
304 is adequate for clean, low-chloride groundwater and is the economical choice for irrigation. Choose 316L for slightly aggressive water, coastal sites, and municipal supply where long service life matters more than unit cost. For brackish water or chloride above about 500 mg/L, consider duplex 2205.
Can you manufacture non-standard diameters or slots?
Yes. Standard range is 25 mm to 1200 mm diameter with slots from 0.10 mm to 3.0 mm, but non-standard sizes, mixed slot arrangements, special connections and custom lengths are routine. Send a drawing or the well design parameters and we will confirm feasibility.
What is your minimum order quantity and lead time?
There is no fixed MOQ — it depends on whether the size is in stock and how custom the specification is. Samples can be ordered to check quality. Production is typically 15–30 days after order confirmation, depending on quantity and customisation.
How are the screens packed for export?
Screens are wrapped in plastic film or bubble bags with wooden strips, then packed in wooden cases or crates lined with waterproof material to protect the wire surface in sea freight. Custom packing and marking are available.
Do you provide installation and well design support?
Yes. We advise on slot selection from formation samples, screen sizing and open area for entrance velocity, gravel pack gradation, and connection detail. Technical guidance continues after delivery.
Request a Quote
Send the five details below and you will get a specification and price, usually within one working day. Missing some of them is fine — send what you have and we will advise on the rest.
- Outer diameter, or the borehole and casing size
- Slot size required, and the formation description if known
- Total length and preferred section length (3 m or 6 m)
- Material grade — 304, 316L, duplex or carbon steel
- End connection — thread, flange, welded ring, or drawing
Direct contact
E-mail: sales@oasiswellscreens.com
Tel: +86-373-2947626
Address: Xuanhe West Road, Fengquan District, Xinxiang City, Henan, China
Technical help — if you would rather have us advise before you commit to a specification, send a formation sample or a sieve analysis along with the well depth and target yield. We will come back with a recommended slot, open area and screen size.
| SIZE | OD | SLOT SIZE | LENGTH(M) | COLLAPSE STRENGTH(PSI) | TENSILE WEIGHT(TON) | RODS |
| 4 | 117 | 0.04 | 3 | 395 | 6 | 3.8MM/22 |
| 4 | 114.3 | 0.04 | 3 | 395 | 6 | 3.8MM/22 |
| 6 | 168.3 | 0.04 | 3 | 252 | 8 | 3.8MM/32 |
| 8 | 219.1 | 0.01 | 3 | 399 | 10.5 | 3.8MM/48 |
| 8 | 219.1 | 0.02 | 3 | 370 | 10.5 | 3.8MM/48 |
| 8 | 219.1 | 0.04 | 3 | 323 | 10.5 | 3.8MM/48 |
| 10 | 273.1 | 0.01 | 3 | 206 | 11 | 3.8MM/50 |
| 10 | 273.1 | 0.02 | 3 | 191 | 11 | 3.8MM/50 |
| 10 | 273.1 | 0.04 | 3 | 167 | 11 | 3.8MM/50 |
Slot Size (mm): or as per customers’ requirement
Material: carbon steel, stainless steel (304, 316L etc.)
Unit length up to 6m.
Diameter from 25mm to 1200mm
Open area up to 60%
End Connection: beveled or thread coupling
The above data is for reference only, actual information is subject to the drawings
