20-721 — Collar Stop — Kynar PVDF

A float level switch like the 20-721 is a point-level device: a float rides the liquid and actuates a magnetic reed switch at a set height, giving a simple on/off signal — no power, no firmware, no calibration. "Sensors" usually means continuous measurement (ultrasonic, radar, capacitive). ERECTA SWITCH targets reliable discrete-point control.

Consider media chemistry (pick PP, AC, or KR), liquid specific gravity, operating temperature and pressure, mounting style, number of switch points, and electrical contact rating. Compac will spec it from your application — request a free evaluation sample.

Choose the material to match the media: Polypropylene (PP) for general aqueous, acids, and bases; Acetal (AC/Delrin) for solvents, fuels, and hydrocarbons; Kynar PVDF (KR) for aggressive or harsh chemicals. Most ERECTA SWITCH models are offered in all three materials; some are material-specific, so check the product page for the model you need.

ERECTA SWITCH offers vertical top-mount, bulkhead, and extended-stem configurations, plus side-mounted single-point models. The mount style is part of the model number — select the configuration that matches your tank geometry.

Point detection is repeatable and mechanical. The trip height on the 20-721 is set by the 10-715 Precision Nipple, ordered separately in 1-inch increments (1″–70″), so you place the switch point exactly where the application needs it.

It depends on the series, and the derate matters more than the headline. Series 10 is rated 100 PSI, Series 15 50 PSI and Series 20 20 PSI — each at 20°C, each derating to zero at 90°C, so a hot line has no pressure allowance left. Series 20 sits lowest by design: its float sections are thin-walled, and sustained pressure can crush them. Temperature follows the material — on Series 10, PP: 180°F, AC: 200°F, KR: 280°F.

A single switch detects one point. For high-plus-low detection (or more), use a multi-level extended-stem set that places multiple reed points on one stem, giving you independent high and low signals from a single mounting hole.

The 20-721 uses a magnetic reed switch wired in series with your relay or controller. Contact rating is 70 VA / 50 W resistive (UL File E70063). The switch ships with lead wires — connect directly to your control circuit.

No. The 20-721 is a mechanical float actuating a sealed reed switch — there is nothing to calibrate or power. This is a reliability advantage over electronic sensors that can drift over time.

Inspect that the float moves freely (check for debris or scaling), then test reed continuity with a multimeter. Because ERECTA SWITCH is modular, you replace only the individual component — switch, float, connector, or fitting — instead of the whole assembly.

Standard ERECTA SWITCH models are not rated for hazardous (Class I / Div) areas. For flammable-service applications, contact Compac engineering to discuss your requirements and available options.

The 20-721 is used for pump start/stop control, high-level overflow protection, low-level dry-run protection, and tank or reservoir level alarms in OEM equipment. The modular ERECTA SWITCH system is built into laundry, HVAC, water-treatment, hydraulic, and chemical-handling machinery.

It is the only fully modular, off-the-shelf liquid level switch system: switch, float, connector, fitting, and nipple are independently field-replaceable and stocked. OEMs configure exactly what they need with no minimums and short lead times. Made in Paradise, California; RoHS compliant.