VITON or EPDM? How to pick the seal that survives your chemical
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VITON (FKM) seals resist acids and petroleum solvents. EPDM seals resist bleach, chlorine, caustics and ketones like acetone. They are close to opposites, and picking the wrong one is the single most common reason a professional sprayer leaks, perishes or fails early. Here is how to get it right the first time.
The rule of thumb
| Seal | Use it for | Keep it away from |
|---|---|---|
| VITON (FKM) | Acids, descalers, petroleum solvents, brake cleaner, concrete sealers | Acetone and other ketones, long-term bleach contact |
| EPDM | Bleach and chlorine, caustics, alkaline degreasers, acetone | Acids, petroleum solvents |
| NBR (nitrile) | Oils, water-based and non-corrosive chemicals | Aggressive acids, solvents and bleach |
Why the wrong seal fails
The tank rarely fails. The O-rings and gaskets do. An incompatible chemical makes the seal swell, harden or crack, and then the sprayer loses pressure, drips from the pump, or leaks chemical onto the operator. With aggressive chemicals that can happen in weeks. The seal material is a fraction of the unit's cost, which is why we always start with the chemical, not the sprayer.
The acetone trap
Acetone is a solvent, so most people reach for a solvent-rated VITON unit. That is the classic mistake. Acetone and other ketones such as MEK destroy VITON quickly. They need EPDM, and even EPDM is best available rather than perfect for strong acetone. For solvent and acetone mixes, ask us about the Klager MASTER SOLVE+, which is built for exactly that job.
What about bleach?
General compatibility charts prefer EPDM for sodium hypochlorite, and that is our default guidance. Some manufacturers, including Klager and Gloria, rate specific bleach-resistant models that pair VITON seals with a bleach-rated spring set. Both approaches work because the whole build is specified for hypochlorite, not just the O-ring. The short version: buy a unit sold as bleach-resistant, and confirm the concentration against the SDS.
How strong an acid can you spray?
The Klager acid-resistant range is rated for most dilute acids, including 25 per cent hydrochloric, 30 per cent sulphuric, 30 per cent phosphoric, 20 per cent acetic, and 10 per cent nitric, citric and hydrofluoric acid. If your acid is stronger or hot, talk to us before you buy.
Re-seal, do not replace
If your sprayer is already leaking, the fix is usually a genuine seal kit, not a new unit. We stock VITON and EPDM seal kits for Klager, Gloria and the other brands we carry, so the same tank keeps working for years.
Frequently asked questions
Which seal do I need for hydrochloric acid?
VITON. Klager acid-resistant units are rated to 25 per cent hydrochloric acid. Check your concentration on the SDS.
Can one sprayer handle both acids and bleach?
Usually no. Acids want VITON and bleach wants an EPDM or bleach-rated build. Sites that run both usually keep two units, clearly labelled.
What seal does a strong degreaser need?
Most strong degreasers are caustic, so EPDM. Solvent-based degreasers want VITON. The SDS tells you which family you are in.
How do I know which seal my sprayer has?
It is on the datasheet and usually on the label. If you are not sure, send us the model and we will confirm it.
Not sure where your chemical lands? Use the Chemical Compatibility Guide, or request a quote and tell us the chemical. We will match the seal for you.