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ERECTA SWITCH Product Family

Series 5 Flow Switches & Indicators

Compact piston-type magnetic reed switches for precise OEM flow detection. Five factory set points from 0.10 to 1.00 GPM — plus ultra-low-flow models sensing down to 0.008 GPM. Built-in clean-out port for in-line service.

5
Factory Set Points
3
Material Options
.008
GPM Ultra-Low
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5-20 Angle Body Flow Switch — the core of the Series 5 flow detection system
PP Acetal PVDF Kynar
Product Categories How It Works Set Points Specifications Materials FAQ
Product Categories

Choose Your Configuration

Three subcategories cover every flow detection need — from standard switches and visual indicators to ultra-low-flow models and field-replaceable accessories.

5-20 Angle Body Flow Switch

Flow Switches / Sets

The core product line. Angle body (5-20), straight body (5-21), high-flow (5-21H), low-flow (5-20-LF), and wire receptacle (5-30) configurations. Five factory set points. Built-in clean-out port for in-line service.

5-20 · 5-20-LF · 5-21 · 5-21H · 5-30
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5-19 Indicator Flow Switch Set

Flow Indicators / Switches / Sets

Visual confirmation of flow — the 5-18 provides sight-only indication, while the 5-19 combines visual indication with electrical switching output in a single device. See flow at a glance.

5-19 · 5-18
In Stock
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Flow Switch Accessories — fittings and replacement poppets

Flow Switch Accessories

Accessory fittings for the 9/16 UNF bosses (adapting to various pipe thread sizes), replacement low-flow poppets (5-16), and low-flow trim sets (5-20-LFT) to convert standard switches to ultra-low-flow operation.

Fittings · Poppets · Trim Sets
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Series 5 piston-type magnetic reed flow switch — cutaway view
Operating Principle

Piston-Type Magnetic Reed Switch

A simple, reliable mechanism with no moving seals and no external adjustments. Fluid flow pushes a spring-loaded poppet against a calibrated titanium spring. When flow exceeds the factory-set threshold, the poppet's embedded magnet actuates a hermetically sealed reed switch.

  • ✓ No moving seals — nothing to wear out or leak in the flow path
  • ✓ Titanium spring — corrosion-proof calibration element sets the flow threshold
  • ✓ Sealed reed switch — hermetically isolated from the process media
  • ✓ Built-in clean-out port — service the poppet and spring without removing from line
  • ✓ 5 factory set points — 0.10, 0.25, 0.50, 0.75, and 1.00 GPM
  • ✓ Vertical springless operation — remove spring and mount vertically for ultra-low flow detection
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Flow Set Points

Factory-Calibrated Precision

Every Series 5 flow switch ships with a precision factory-set flow threshold. The set point is specified in the part number suffix (e.g., 5-20-PP-0.50 = 0.50 GPM).

Set Point Flow Rate (GPM) Configuration Applications
0.008 GPM Ultra-low flow 5-20-LF set, vertical mount, spring removed Drip detection, medical dosing, chemical metering
0.042 GPM Ultra-low flow 5-20-LF set, spring installed Low-flow cooling loops, condensate monitoring
0.10 GPM Standard low flow Standard switch with titanium spring Instrument cooling, small equipment protection
0.25 GPM Standard Standard switch with titanium spring HVAC flow confirmation, process monitoring
0.50 GPM Standard (most popular) Standard switch with titanium spring General purpose flow detection, equipment protection
0.75 GPM Standard Standard switch with titanium spring Pump protection, recirculation monitoring
1.00 GPM Standard high flow Standard switch with titanium spring Process flow confirmation, industrial cooling

Standard set points with titanium spring:

0.10 GPM 0.25 GPM 0.50 GPM 0.75 GPM 1.00 GPM

Ultra-low flow (5-20-LF kit):

0.042 GPM (with spring) 0.008 GPM (springless vertical)
Technical Specifications

Series 5 Ratings

Core electrical and mechanical specifications for all Series 5 flow switches and indicators.

Parameter Rating Notes
Electrical Rating (standard) 0.5A @ 100VDC / 0.8A @ 120-240VAC Pilot Duty Reed switch, resistive load
Electrical Rating (5-Amp sets) 5A @ 120/240VAC With solid state relay
Contact Configuration SPST — Normally Open (NO) Closes when flow exceeds set point
Flow Range 0.008 GPM to 1.00 GPM Model and configuration dependent
Operating Temperature -20°F to +180°F (-29°C to +82°C) Material-dependent upper limit
Maximum Pressure 150 PSI At ambient temperature
Port Connections 9/16 UNF female bosses (built-in) Use with accessory fittings for pipe thread adaptation
Body Style Angle (5-20) / Straight (5-21) Same switching mechanism in both
Spring Material Titanium Corrosion-proof; removable for ultra-low flow
Certifications RoHS Compliant Made in USA — Paradise, California
Material Selection

Three Materials. Every Chemical Environment.

Every Series 5 product is manufactured in three thermoplastics. The material suffix in the part number (-PP, -AC, -KR) identifies the version.

Polypropylene

PP — suffix -PP

The versatile workhorse. Excellent resistance to water, soaps, detergents, and dilute acids at moderate temperatures. The most popular choice for water-based flow applications.

Compatible With
Water Soaps Detergents Light Acids Caustics

Acetal

AC — suffix -AC

Engineered for hydrocarbon environments. Superior performance with oils, fuels, and hydraulic fluids where polypropylene falls short. Higher mechanical strength.

Compatible With
Oil Gasoline Diesel Hydraulic Fluid Solvents

PVDF Kynar

KR — suffix -KR

Maximum chemical resistance for the most aggressive media. Withstands concentrated acids, caustics, and oxidizers where other plastics fail. Premium choice for chemical processing.

Compatible With
Harsh Acids Strong Caustics Oxidizers Chlorine HF
Frequently Asked Questions

Series 5 FAQ

Series 5 flow switches use a piston-type magnetic reed switch mechanism. Fluid flow pushes a spring-loaded poppet (piston) against a calibrated titanium spring. When flow exceeds the factory-set threshold, the poppet's magnet actuates a sealed reed switch, providing a clean electrical signal. No moving seals, no external adjustments.
Standard Series 5 flow switches are available with five factory-set flow points: 0.10 GPM, 0.25 GPM, 0.50 GPM, 0.75 GPM, and 1.00 GPM (with titanium spring installed). For ultra-low flow detection, the 5-20-LF Low Flow Switch Set actuates at 0.042 GPM with spring, or 0.008 GPM with spring removed and vertical mounting.
The 5-20 is an angle body design — inlet and outlet ports are at 90° to each other. The 5-21 is a straight body (inline) design — inlet and outlet are aligned. Both use the same switching mechanism and are available in the same materials and set points. Choose based on your plumbing layout.
The 5-18 is a visual-only flow indicator — it provides visible confirmation that flow is present without an electrical switching output. It uses the same piston mechanism but replaces the reed switch with a visual indicator. The 5-19 combines both functions: visual indication plus electrical switching in one device.
Yes. All 5-20 and 5-21 flow switches feature a built-in clean-out port that allows removal and replacement of the spring and poppet without disassembling your plumbing. This is a significant maintenance advantage over competitive flow switches that require full line disconnection for service.
All Series 5 flow switches are manufactured in three chemically-resistant thermoplastics: Polypropylene (PP) for water, soaps, and light chemicals; Acetal (AC) for oils, fuels, and hydraulic fluids; and PVDF Kynar (KR) for harsh acids, caustics, and aggressive chemical environments. The material code is part of every part number suffix.

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