The liquid you’re measuring drives nearly every material decision on the Float Switch. A bad spec leads to premature failure, process contamination, or both. A good spec runs for years without a callback.

The things that matter most: chemistry, temperature, pressure, specific gravity, vibration, viscosity, what else is in the tank, and tank maintenance.

Chemical Compatibility

The wetted components (float, stem, seals, fittings) have to resist whatever they’re sitting in. Polypropylene and 304 stainless cover most water-based applications, including potable water, condensate, and general industrial water. Saltwater and other chloride-bearing liquids will pit 304 over time, even at low concentrations. The molybdenum content in 316 gives it better chloride resistance, which is why coastal installations, brine tanks, and chlorinated process water typically call for 316 or higher alloys.

Acids are where stainless reaches its limits. Dilute nitric is fine on 316, but sulfuric and hydrochloric will eat standard stainless across most concentrations. PTFE, or specialty plastics handle that service. Concentration and temperature both matter: a chemical that’s compatible at room temperature and 10% strength may be aggressive at 60°C and 50%. Always check the compatibility chart against actual operating conditions, not just the chemical name.

Caustics flip the script. Sodium hydroxide and potassium hydroxide are usually fine on stainless but can degrade some plastics over time. Hypochlorite solutions used in water treatment and disinfection are tough on standard stainless and often push the spec toward PTFE or specially passivated alloys.

Hydrocarbons, oils, and fuels usually work fine with stainless steel, but the seals matter as much as the metal: Buna-N and Viton are common, and the o-rings often fail before the wetted body does. Solvents get application-specific fast, so check the exact chemical and concentration against a compatibility chart.

Deionized and ultrapure water deserve a separate mention. They’re aggressive in their own way because they leach ions from any material they contact. Standard stainless can shed measurable amounts of iron and chromium into high-purity water, which matters in semiconductor, pharma, and lab applications. Electropolished 316L or PTFE wetted parts are typical for those uses.

If the liquid is a proprietary blend, ask the chemical supplier for a compatibility chart before specifying anything. And do not overlook the threaded fitting and any o-ring or gasket at the mounting connection. Those threads are wetted parts too.

Temperature

Plastics that work at room temperature can soften or deform when the liquid runs hot. Polypropylene tops out around 200°F. PVC is lower, typically 140°F. PTFE handles up to 500°F but cost climbs with temperature rating. Stainless handles heat without issue, but it transfers heat readily, which matters when the conduit, housing, or downstream electronics are heat-sensitive.

Cold-side limits matter too. Some plastics get brittle below freezing, and many seal materials lose elasticity as temperatures drop. For applications cycling between hot and cold, thermal expansion mismatches between the float, stem, and any fittings can cause leaks at the mounting connection or shifted set points over time.

If the tank sees steam exposure during cleaning or a process upset, the spec needs to handle the worst-case temperature, not the normal operating temperature.

Specific Gravity

The float has to float. Standard floats are calibrated for water at a specific gravity of 1.0. Lighter liquids will sit lower in the float or fail to lift it at all. Gasoline runs around 0.74, diesel about 0.85, ethanol about 0.79, and most light hydrocarbons fall in that range. Heavier liquids ride the float higher than expected, which throws off your set points. Brine solutions can run 1.1 to 1.2, glycol mixes vary by concentration, and some chemical solutions push higher still.

Foam and aeration are separate problems. A heavily aerated liquid behaves like something between liquid and gas, and a standard float may not respond cleanly to the surface. Larger floats or specialty designs help in those applications, but flag the issue early so we can recommend the right configuration.

Tell us the specific gravity and we can match the float density to the application.

Particulates and Coatings

Liquids carrying solids, fibers, or sludge will foul a standard float over time. Same goes for liquids that leave a film or scale. Smooth float geometry, larger float diameters, or stem designs without sliding contact tend to hold up better in those conditions.

Crystallization is its own category. Salt brines, sugar solutions, and some chemical liquids leave crystalline deposits at the air-liquid interface as they evaporate. Those deposits can lock a float in place. Sticky liquids like latex, paint, and heavy oils coat the float and add weight over time, gradually shifting the trigger point. In tanks with biological growth, regular cleaning is usually a better answer than trying to spec around it, but smooth surfaces and stainless steel slow the buildup.

Tanks with oil layered on water need a float weighted to ride below the oil layer, otherwise it tracks the wrong surface instead of the actual liquid level. The same logic applies to any stratified liquid.

Vapor Space Exposure

The wetted parts above the liquid line still see whatever is in the headspace, and that vapor phase is sometimes more aggressive than the liquid below it. Volatile organic solvents concentrate in the headspace. Acid tanks generate corrosive mists. Ammonia and chlorine systems can attack fittings and electrical connections that never touch the liquid itself. When specifying for those applications, treat the entire stem, any conduit fitting, and the vent path as wetted.

Cleaning Chemistry

In food, beverage, and pharmaceutical applications, the cleaning cycle often drives material selection more than the process fluid does. CIP (clean-in-place) cycles typically run caustic at 160 to 180°F followed by an acid rinse, then sometimes steam sterilization at 250°F or higher. A switch rated for the product line can fail under repeated CIP exposure if the seals or float material were not specified for the cleaning chemistry.

When the application includes CIP or SIP, send us the cleaning protocol along with the process spec. Specifying the right materials at the start costs less than retrofitting after the first cleaning cycle reveals the wrong choice.

When to Send a Spec Sheet

If the liquid is unusual, the temperature is high, or you’re working with a chemical mixture, send the SDS or a description of the application. We can spec the right materials before production starts, which is faster than pulling a degraded switch from the field and starting over.

Innovative Components manufactures float switches in stainless steel, polypropylene, PTFE, and other materials with custom configurations and no minimum orders. Made in the USA with fast turnaround and a real person on the phone. Browse our float switches or call us to talk through your application.