Closed-loop heating water
with corrosion inhibitor | 60–110°C | Cast iron or stainless steel pump casing; stainless steel shaft; ceramic or silicon-carbide mechanical seal faces | EPDM is commonly suitable for water-based heating systems. Confirm compatibility with the specific inhibitor package. | Untreated carbon steel and unsuitable elastomers may corrode or swell. | Closed systems generally contain less oxygen than open systems, reducing corrosion risk. Verify the inhibitor concentration, pH, system pressure, and maximum temperature before final selection. |
| Open-loop domestic hot-water circulation | 5–65°C, depending on the system design | Stainless steel casing and wetted components; bronze may be suitable in some potable-water applications when permitted by local regulations | Use drinking-water-approved seals and elastomers. EPDM is often selected for hot-water service when certification and temperature limits are satisfied. | Standard cast iron can release corrosion products and is generally unsuitable for potable-water wetted parts. | The pump must comply with applicable potable-water material and hygiene requirements. Check local regulations, certification, disinfection temperature, and water chemistry. |
| Chilled water with glycol | −10–25°C | Cast iron or stainless steel casing; stainless steel shaft; materials confirmed for the selected glycol concentration | EPDM is commonly compatible with propylene glycol and many ethylene-glycol mixtures, but the exact formulation must be checked. FKM may be considered for selected fluid and temperature ranges. | Natural rubber and some low-cost elastomers may deteriorate. Glycol additives can change compatibility compared with water alone. | Higher glycol concentrations increase viscosity and can reduce pump flow and efficiency. Select the pump using the actual mixture concentration, viscosity, and minimum temperature. |
| Seawater or chloride-rich water | 5–40°C | Duplex stainless steel, super-duplex stainless steel, titanium, or other materials specifically qualified for chloride exposure | Use elastomers and seal faces rated for saltwater. Silicon carbide seal faces are often considered for abrasive or chemically demanding water service. | Cast iron, carbon steel, standard bronze, and some stainless-steel grades can suffer corrosion, pitting, or crevice attack. | Material selection depends strongly on chloride concentration, oxygen level, velocity, temperature, and galvanic couples. Avoid mixing dissimilar metals without evaluating galvanic corrosion. |
Mildly acidic water
approximately pH 5–6 | 10–50°C | 316 stainless steel may be suitable for some conditions; polymer-lined or engineered-polymer wetted parts may be considered after chemical review | EPDM, FKM, or PTFE may be suitable depending on the acid type and concentration. Chemical compatibility must be checked against the complete seal assembly. | Cast iron and lower-alloy steels may corrode rapidly, especially with dissolved oxygen or chlorides. | pH alone is not enough to select materials. Identify the acid species, concentration, conductivity, oxidizing conditions, and presence of solids. |
Alkaline cleaning solution
such as diluted caustic solution | 20–90°C | 316 stainless steel, nickel-based alloys, or chemically resistant engineered polymers, subject to concentration and temperature | PTFE is broadly resistant to many caustic chemicals. EPDM can work with selected alkaline solutions; confirm concentration and temperature limits. | Aluminum, zinc, and some elastomers may be attacked. Stainless steel can also be unsuitable in highly concentrated or high-temperature caustic service. | Confirm the chemical concentration during both normal operation and cleaning cycles. Consider thermal expansion, crystallization, and the possibility of dry running. |
Lightly abrasive water
with suspended sand or mineral particles | 5–60°C | Hardened stainless steel or abrasion-resistant alloy components; silicon-carbide seal faces; replaceable wear components where available | Choose seal materials designed for solids-containing fluids. A flushed or separated seal arrangement may be required for higher solids loads. | Standard carbon-ceramic seal faces and soft metals can wear quickly. Fine particles may damage close-clearance components. | Use filtration, settling, or a suitable strainer when possible. Particle size, concentration, hardness, and pump velocity are critical to service life. |
| Water containing iron or manganese deposits | 5–70°C | Stainless steel wetted parts where deposit formation is severe; otherwise, properly protected iron-based components may be acceptable in closed systems | Use seals that tolerate the temperature and cleaning chemicals. Design the system to permit inspection and cleaning. | Narrow passages and close-clearance parts can become restricted by deposits, reducing flow and increasing power demand. | Material changes alone may not solve fouling. Water treatment, periodic cleaning, adequate velocity, and an accessible strainer can be equally important. |
| Thermal oil or synthetic heat-transfer fluid | 80–300°C, depending on the fluid | Materials specifically rated for the selected heat-transfer fluid and temperature; stainless steel may be suitable in many systems | EPDM is generally unsuitable for many hydrocarbon-based thermal oils. FKM, PTFE, or other high-temperature materials may be considered after compatibility testing. | Water-service seals and elastomers may swell, harden, or lose sealing performance. Standard circulator designs may not be suitable. | Check viscosity at operating temperature, vapor pressure, oxidation stability, seal temperature, and required cooling arrangements. Use a pump specifically designed for thermal-oil duty. |
| Water with dissolved oxygen and frequent make-up | 5–90°C | 316 stainless steel or corrosion-protected materials; cast iron may be acceptable only when water chemistry and system design support it | Use elastomers compatible with the water treatment chemicals. Select seal faces that tolerate possible corrosion products and intermittent operation. | Repeated oxygen ingress accelerates corrosion in unprotected ferrous components, particularly where deposits or stagnant zones exist. | Investigate the source of make-up water, dissolved oxygen, conductivity, pH, chlorides, and treatment chemicals. Improving system control may extend pump life more effectively than changing materials alone. |
| Mixed-fluid system with uncertain chemistry | Project-specific | 316 stainless steel or a higher-alloy or polymer-lined construction selected after a documented compatibility review | PTFE can provide broad chemical resistance, but its mechanical and temperature limits still require verification. Select elastomers based on the actual fluid blend. | Do not rely on a general label such as “chemical water” or “process liquid.” Unidentified additives can cause rapid seal or casing failure. | Obtain the safety data sheet and full composition, then review concentration, temperature, pressure, viscosity, solids, conductivity, and cleaning conditions with the pump manufacturer or materials specialist. |
