Different Types of Pump Seals: Materials, Chemical Resistance & What They’re Used For

Pump seals are small parts, but they do a big job. In a pump, the shaft has to spin while the liquid stays inside the pump housing. The seal is what helps stop water, chemicals, or other fluids from leaking out around that rotating shaft.

In rural water systems, pump seals are commonly found in jet pumps, booster pumps, circulation pumps, transfer pumps, treatment equipment, and some shallow well pump setups. When the wrong seal material is used, the pump may leak early, overheat, wear out, or fail completely. Mechanical seals are commonly selected based on fluid type, pressure, temperature, cleanliness, and whether the liquid is abrasive or chemically aggressive.

For homeowners, camps, farms, and rural properties around Thunder Bay and Northwestern Ontario, understanding pump seal materials can help explain why one pump lasts for years while another starts leaking after a short period of use.

What Is a Pump Seal?

A pump seal is designed to stop fluid from escaping where the motor shaft or pump shaft passes through the pump body. Most modern pumps use a mechanical seal, which has two very flat sealing faces pressed together. One face usually spins with the shaft, while the other stays stationary inside the pump.

A mechanical seal is not just one material. It is made up of several parts:

• Seal faces — carbon, ceramic, silicon carbide, tungsten carbide, or stainless combinations

• Elastomers — Buna-N, EPDM, Viton/FKM, PTFE, or specialty rubber materials

• Metal parts — stainless steel, 316 stainless, Hastelloy, or other alloys

• Springs or bellows — used to maintain pressure between the faces

This is where confusion happens. When someone says “stainless seal,” they may be talking about the metal hardware, spring, case, or stationary face — not necessarily the best face material for every water or chemical application. Stainless steel can be useful, but it is not automatically the most chemical-resistant or wear-resistant choice.

Common Types of Pump Seals

1. Packing Seals

Older pumps may use packing instead of a modern mechanical seal. Packing is a rope-like material compressed around the shaft. It is adjusted by tightening a gland.

Packing can work well in some industrial and agricultural applications, but it usually allows a small amount of controlled leakage for lubrication. It is not as common in smaller residential jet pump systems as mechanical seals.

Best for: older pumps, some agricultural pumps, larger serviceable pump systems

Downside: requires adjustment and may drip by design

2. Standard Mechanical Seals

This is the most common type found in many small pumps. A standard mechanical seal uses two seal faces, an elastomer, and a spring system to hold tension.

For clean water, the common setup is often carbon against ceramic with a Buna-N rubber elastomer. Carbon and ceramic combinations are often used for clean water and neutral pH applications.

Best for: clean well water, jet pumps, transfer pumps, light-duty water applications

Downside: not ideal for sand, grit, aggressive chemicals, or dry running

3. Cartridge Mechanical Seals

A cartridge seal comes pre-assembled as one unit. The seal faces, spring, sleeve, and hardware are built together, which reduces installation errors.

Cartridge seals are more common in larger commercial, municipal, industrial, or higher-end pump systems. They usually cost more up front, but they can save time and reduce mistakes during installation. Cartridge seals are designed as self-contained assemblies that reduce setup and measurement errors compared with component seals.

Best for: larger pumps, commercial systems, higher-value equipment

Downside: more expensive than basic component seals

4. Balanced and Unbalanced Seals

A balanced seal is designed to reduce the hydraulic force pushing the seal faces together. This helps reduce heat and wear, especially in higher-pressure applications.

An unbalanced seal is simpler and often cheaper, but it is better suited to lower-pressure applications. Balanced seals are commonly recommended for higher pressure or higher temperature situations, while unbalanced seals are more common in lower-pressure service.

Best for balanced seals: higher pressure, hotter water, more demanding pumpsBest for unbalanced seals: basic low-pressure water service

5. Pusher and Non-Pusher Seals

A pusher seal uses a spring and O-ring that move slightly as the seal wears. These are common and versatile.

A non-pusher seal often uses a bellows design instead. Bellows seals can be useful where heat, dirt, or certain chemicals are a concern. Pusher seals use spring force and secondary elastomers to maintain closing force, while non-pusher designs use metal or elastomeric bellows.

Best for pusher seals: general-purpose pump service

Best for non-pusher seals: dirty, hot, or more demanding applications

Pump Seal Face Materials

The seal faces are the two flat surfaces that run against each other. This is one of the most important parts of choosing the right seal.

Carbon / Ceramic Seals

This is one of the most common seal combinations for clean water pumps.

Carbon is often used because it has good self-lubricating properties. Ceramic is hard, smooth, and affordable. Together, carbon and ceramic are a dependable choice for normal clean water service.

Good for:

• Clean well water

• Jet pumps

• Booster pumps

• Light-duty transfer pumps

• Neutral pH water

Not ideal for:

• Sand or grit

• Heavy iron sludge

• Harsh chemicals

• Dry running

• Sudden temperature shock

• 
  

Carbon/ceramic is a great general-purpose choice, but it is not the strongest option for dirty or abrasive water.

Silicon Carbide Seals

Silicon carbide is a major upgrade from basic ceramic. It is very hard, very wear-resistant, and has strong chemical resistance. Silicon carbide is often used when the pumped liquid is more abrasive, more chemical-heavy, or more demanding than clean water.

You may see:

• Carbon vs. silicon carbide

• Silicon carbide vs. silicon carbide

Carbon against silicon carbide is a strong upgraded combination for many water and light chemical applications. Silicon carbide against silicon carbide is often used where abrasion, wastewater, slurry, or chemical-rich fluids are involved.

Good for:

• Abrasive water

• Dirty water

• Water with grit or solids

• Some chemical feed systems

• Wastewater or sump-related pump applications

• More demanding water treatment equipment

Not ideal for:

• Dry running without proper design

• Cheap low-duty pumps where the cost is not justified

• Applications where manufacturer compatibility is unknown

For rural water systems with sand, sediment, or iron buildup, silicon carbide can be a better choice than a basic carbon/ceramic seal.

Tungsten Carbide Seals

Tungsten carbide is another high-performance seal face material. It is very tough and has excellent impact resistance. It is often selected for physically demanding applications where the seal faces may experience vibration, pressure, or abrasive conditions.

Tungsten carbide is considered a strong, resilient seal face material with excellent particulate and impact resistance, although it is usually a higher-cost option.

Good for:

• High-pressure pump applications

• Abrasive service

• Impact-prone service

• Industrial pumps

• Heavy-duty transfer applications

Not ideal for:

• Low-cost residential pumps where it is overkill

• Certain chemical applications unless binder compatibility is checked

• Applications where silicon carbide would be a better chemical choice

One important note: tungsten carbide can come with different binders, such as nickel-bound or cobalt-bound versions. Chemical resistance can change depending on the binder, so the exact seal material matters.

Stainless Steel Seal Parts

Stainless steel is commonly used in the metal hardware of a seal, including springs, cups, retainers, and cases. Some seals may also use stainless as part of the face combination.

304 stainless is common and affordable. 316 stainless is usually preferred where there is more chemical exposure, salt, chlorides, or a more aggressive environment. Stainless steel seal faces are generally softer than ceramic, silicon carbide, or tungsten carbide and are not usually the best choice for water with solids or grit.

Good for:

• General corrosion resistance

• Clean water hardware

• Some chemical-resistant seal assemblies

• Food-grade or higher-corrosion applications when 316 is used

Not ideal for:

• Sandy water

• Abrasive service

• High-wear seal face applications

• Strong chemical service without checking compatibility

Stainless is important, but “stainless” does not automatically mean “best seal.” The seal faces and elastomers still need to match the liquid being pumped.

Elastomer Materials: Buna, EPDM, Viton, PTFE and More

The elastomer is the rubber-like part of the seal. It may be an O-ring, boot, cup, wedge, or bellows. Even if the seal faces are high quality, the wrong elastomer can swell, crack, shrink, or fail.

Buna-N / Nitrile / NBR

Buna-N, also called nitrile or NBR, is one of the most common rubber materials in standard pump seals.

Good for:

• Clean water

• Some oils

• General-purpose use

• Lower-cost pump seals

Not ideal for:

• Strong chlorine

• Ozone exposure

• High heat

• Some chemical feed applications

• Aggressive water treatment chemicals

For basic clean water, Buna is common. For chemical feed systems or hotter applications, it may not be enough.

EPDM

EPDM is often used where hot water, steam, glycol, or caustic solutions are involved. It is also commonly used in many water treatment and plumbing-related applications. EPDM is not normally used for petroleum oils or fuels.

EPDM is often chosen for hot water, steam, caustic, and glycol-based systems.

Good for:

• Hot water

• Some chlorine/water treatment applications

• Glycol

• Caustic solutions

• General water treatment equipment

Not ideal for:

• Oil

• Gasoline

• Diesel

• Petroleum-based liquids

For many rural water treatment systems, EPDM can be a strong option when the chemistry matches.

Viton / FKM

Viton is a brand name often used when people mean FKM fluoroelastomer. FKM is known for strong chemical resistance and higher temperature capability compared with basic Buna.

FKM is commonly used for more aggressive chemical and higher-temperature environments, but compatibility still needs to be verified for the exact chemical.

Good for:

• Many chemicals

• Higher temperatures

• Oils and fuels

• Some chemical feed applications

Not ideal for:

• Some hot water or steam applications

• Certain caustics

• Some ketones, amines, and specialty chemicals

• Situations where EPDM would actually be a better match

Viton/FKM is a great material, but it is not universal. The exact chemical matters.

PTFE / Teflon-Type Materials

PTFE is used where very strong chemical resistance is needed. It is not rubbery like Buna, EPDM, or Viton, so it may be used in special O-rings, wedges, or encapsulated designs.

Good for:

• Strong chemical resistance

• Acidic or aggressive chemical applications

• Specialty pump seals

  
  

Not ideal for:

• Cheap standard pump repairs

• Applications needing a soft flexible rubber seal

• Equipment not designed for PTFE-style sealing

  
  

PTFE is usually seen in more specialized seals, not basic residential jet pump seals.

Quick Material Comparison Table

Seal material	Main strength	Best use	Watch out for
Carbon / Ceramic	Affordable, common, good for clean water	Standard jet pumps and clean water pumps	Sand, grit, dry running, harsh chemicals
Carbon / Silicon Carbide	Better wear and chemical resistance	Upgraded water and treatment applications	Higher cost
Silicon Carbide / Silicon Carbide	Excellent abrasion and chemical resistance	Dirty water, slurry, wastewater, chemical-rich service	Needs proper lubrication/design
Tungsten Carbide	Tough, impact-resistant, heavy-duty	High pressure, abrasive, industrial service	Expensive; chemical binder matters
Stainless Steel	Good corrosion-resistant hardware	Springs, retainers, light-duty faces	Not the best face for grit or solids
Buna-N / NBR	Common, affordable elastomer	Clean water and general service	Poorer chemical and heat resistance
EPDM	Good for hot water, glycol, caustic, some water treatment uses	Water treatment, hot water, caustic service	Not for oils or fuels
Viton / FKM	Stronger chemical and heat resistance	Chemicals, oils, higher heat	Not universal; check compatibility
PTFE	Excellent chemical resistance	Specialty chemical service	Less flexible, special designs needed

Why Seal Material Matters in Rural Water Systems

Rural water is not always “just water.” A private water system may contain iron, manganese, sand, sediment, sulphur smell, low pH, chlorine from treatment equipment, salt brine, tannins, or other minerals.

That matters because each condition can attack the pump seal in a different way.

Sand and sediment can scratch seal faces.Iron buildup can cause deposits around the seal area.Dry running can overheat and destroy seal faces.Chemical injection can damage the wrong elastomer.Low pH water can be corrosive to metal parts.High chlorine can attack certain rubber materials.Heat can harden or crack the wrong elastomer.

This is why seal selection should be based on the full system, not just the pump model.

Signs a Pump Seal May Be Failing

A failing pump seal may show up as:

• Water leaking between the pump and motor

• Rust stains or mineral buildup under the pump

• Pump losing prime

• Motor bearing noise from water getting past the seal

• Short cycling or pressure problems

• Reduced pump performance

• Visible dripping from the pump body

• Pump overheating or smelling hot

A leaking seal is often a symptom of a bigger issue. The pump may have run dry, the water may be sandy, the motor bearing may be failing, the impeller may be damaged, or the pump may be operating outside its normal range.

The Best Seal Depends on the Water

There is no single “best” pump seal for every job.

For clean rural well water, a standard carbon/ceramic seal with the proper elastomer may be fine. For water with sand, iron, grit, or chemical treatment, a silicon carbide seal face and upgraded elastomer may be a better choice. For heavy-duty or high-pressure systems, tungsten carbide or cartridge-style seals may be considered. For chemical applications, the exact fluid, concentration, temperature, and pump design must be checked before choosing the seal.

The most important rule is simple:

Match the seal to the water, the pump, and the conditions.

Final Thoughts

Pump seals may be small, but they play a major role in keeping a pump reliable. The wrong seal can lead to leaks, downtime, motor damage, and repeat failures. The right seal material can help a pump handle clean water, abrasive water, hot water, chemical treatment, or heavier-duty service more reliably.

For rural homes, camps, cottages, and private water systems around Thunder Bay and Northwestern Ontario, pump problems should always be looked at as part of the whole system. A seal leak may be caused by the seal itself, but it may also point to dry running, poor water quality, sediment, pressure issues, worn bearings, or pump damage.

At Superior Water & Wells, we help rural property owners understand and repair private water system problems, including pump issues, pressure problems, water treatment concerns, and well water system performance.

Superior Water & Wells

Rural Water Done Right

249 - 979 - 3665

info@superiorwaterwells.ca