6 Best Drum Bung Seals For Preventing Evaporation Of Liquid Fertilizers

Liquid fertilizers are a significant investment for any farm, yet far too many producers lose money simply by letting their inventory evaporate into thin air. A loose or degraded drum bung seal isn’t just a minor oversight; it is a direct drain on your bottom line and a potential hazard for your storage area. By selecting the right gasket for your specific storage conditions, you protect your crop nutrients and maintain the integrity of your supplies throughout the season.

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Rieke K-Style EPDM Seal: Best Overall Gasket

The Rieke K-style EPDM gasket stands out as the industry gold standard for general-purpose farm use. Because Ethylene Propylene Diene Monomer (EPDM) provides excellent resistance to the mild acids and alkaline solutions commonly found in fertilizers, it remains flexible and effective even through fluctuating seasonal temperatures.

This gasket is the most reliable choice for farmers who store their drums in standard sheds or barns where temperature control isn’t an option. Its ability to create a consistent, airtight seal prevents liquid loss and keeps moisture out, which is vital if the product is hygroscopic or prone to diluting when exposed to air.

If the drum storage setup is standard and the fertilizers being used are not overly aggressive, choose the Rieke K-style EPDM seal. It offers the best balance of longevity and cost-effectiveness, making it the default choice for the majority of hobby farming operations.

Tri-Sure Buna-N Gasket: Top Budget-Friendly Pick

When purchasing liquid fertilizer in bulk, keeping overhead low is essential, and the Tri-Sure Buna-N gasket is the primary tool for that mission. These gaskets are extremely affordable and work perfectly for short-term storage or for fertilizers that are consumed quickly within a single growing season.

Buna-N, or nitrile rubber, is well-regarded for its resistance to oils and petroleum products. While it may show signs of degradation faster than EPDM when exposed to heavy UV light or specific caustic fertilizers, it provides an airtight barrier that is more than sufficient for standard usage cycles.

Opt for the Tri-Sure Buna-N gasket if the fertilizer inventory is rotated rapidly and kept out of direct sunlight. It is the pragmatic choice for keeping costs down without compromising the basic protection needed for standard storage.

McMaster-Carr Viton Seal: Most Chemical-Resistant

Not every liquid fertilizer is mild; some specialized high-concentration mixtures or proprietary blends require more robust containment than standard rubber can offer. A Viton seal is the solution for these demanding applications, providing superior resistance to high-temperature degradation and harsh chemical exposure.

Viton is an elite-level fluoroelastomer that refuses to break down or swell even when in contact with aggressive additives that would soften an EPDM or Buna-N seal. For farm operations dealing with concentrated soil amendments or specialized foliar feeds that have a tendency to “eat” through lower-grade gaskets, this investment is mandatory.

The higher price point of Viton is a tradeoff for the peace of mind it provides when storing reactive chemicals. If you are dealing with high-potency or corrosive substances, skip the cheaper alternatives and move directly to a Viton seal to prevent leaks and potential chemical spills.

U.S. Plastic Corp Santoprene: Best for UV Rays

Many hobby farmers store liquid fertilizers in drums situated near the edges of equipment shelters or uncovered outdoor zones. Standard rubber seals can become brittle, crack, and fail when subjected to constant UV exposure, leading to invisible leaks that compromise product quality over time.

Santoprene is a thermoplastic elastomer that bridges the gap between rubber and plastic, offering exceptional resistance to environmental degradation. It is remarkably durable under the intense UV radiation that kills off cheaper gaskets, ensuring the bung seal stays soft and tight despite year-round weather exposure.

This is the definitive choice for any drum stored outside of a fully enclosed building. If the barrel is positioned where the sun hits it for even part of the day, choose Santoprene to avoid the inevitable brittle-failure associated with standard materials.

Greif Poly Vented Bung: Prevents Pressure Buildup

Occasionally, the issue isn’t just about keeping liquid in; it is about managing the pressure that develops inside the drum due to ambient heat changes. If a drum doesn’t breathe, pressure can build up and stress the seams, or, conversely, a vacuum can form that makes extraction a difficult task.

The Greif Poly Vented Bung is specifically engineered to allow for equalization while still preventing the sloshing or evaporation of the liquid fertilizer inside. By incorporating a small, one-way or semi-permeable valve, this bung protects the container structure during those sweltering summer months.

Consider this option for drums that are subject to extreme temperature swings throughout the day. It is a proactive engineering solution that prevents physical damage to the container and keeps the fertilizer stabilized, regardless of the heat index.

Basco EPDM Seal: Fits Coarse Thread Bung Holes

One of the most frustrating aspects of farm maintenance is discovering that a seal simply doesn’t fit the thread profile of the bung hole. Basco offers specialized EPDM seals designed for coarse-threaded bungs, which are common on heavy-duty plastic drums and poly-totes used for bulk agricultural supplies.

These seals provide a thicker cross-section that accommodates the wider gaps of coarse threads, ensuring a flush, watertight fit. Trying to force a fine-thread gasket into a coarse-threaded bung is a recipe for a slow leak that will inevitably lead to crusting around the bung hole and wasted product.

For those managing re-used industrial barrels or large poly-tanks, the Basco EPDM seal is the reliable, no-fuss fix. Ensure the barrel thread profile is identified before purchase, and if it is coarse, this specific seal will prevent the headache of incompatible hardware.

Choosing Your Seal Material: EPDM vs. Buna-N

Deciding between EPDM and Buna-N often comes down to the chemical composition of the fertilizer. EPDM is generally the superior choice for water-based fertilizers and general agriculture chemicals, as it has high resistance to ozone, weather, and aging.

Buna-N, conversely, shines when there is any possibility of petroleum-based contaminants or if the equipment being used has residual traces of oil. While EPDM can swell or fail if exposed to oils, Buna-N thrives in those specific environments while remaining cost-effective for large-volume storage.

Evaluate the specific storage location and the chemical nature of the product being used. If the fertilizer is purely water-soluble and the storage is exposed to the elements, EPDM is the clear winner; if there is any chance of oil contamination, lean toward Buna-N.

How to Install a Bung Seal for a Perfect Fit

Installing a seal seems simple, but a misaligned gasket is as useless as having no gasket at all. First, clean the surface of the bung hole and the drum threads thoroughly, as dried fertilizer residue can prevent a tight, flush seal.

Ensure the gasket is seated flat against the flange of the bung plug before screwing it into the drum. Tighten the bung with a proper wrench until firm, but avoid over-torquing, which can cause the gasket to pinch or deform and actually create a gap for evaporation to occur.

Periodically check the tension of the bung after the first few days of storage, especially if the temperature has changed significantly. A quick “snug” check can ensure the seal remains tight as the material settles into its position.

Fine vs. Coarse Threads: Know Your Drum Type

The difference between fine and coarse threads is the difference between a secure seal and a ruined batch of fertilizer. Standard steel drums usually utilize fine threads, while high-density polyethylene (HDPE) drums and plastic totes almost exclusively utilize coarse threads.

Attempting to cross-thread a bung is the most common way to ruin a drum’s integrity, leading to a permanent leak. Before buying a new seal, unscrew the existing bung and look at the “pitch” of the threads; if they are wide and deep, it is coarse, and if they are tight and shallow, it is fine.

Matching the seal to the thread type is non-negotiable for safety and liquid retention. If there is ever any doubt, keep a spare bung and gasket of each type in the shop; the small investment saves significant time during critical planting windows.

Inspecting Seals for Leaks and Degradation

A regular inspection routine is the cheapest insurance policy against losing expensive fertilizer. Once a month, run a gloved finger around the base of the bung and the edge of the seal to check for “weeping” or sticky residue that indicates a micro-leak.

Watch for visual signs of degradation, such as cracking, peeling, or a “flattened” appearance where the seal no longer returns to its original shape. If the seal has lost its elasticity, replace it immediately, as it will no longer provide a consistent barrier against the environment.

Remember that seals are consumables, not permanent fixtures. Treat them like oil filters or air filters on a tractor; replace them at least once a season or whenever the drum is cleaned and refilled to ensure the integrity of the next batch.

Effective fertilizer management relies on the small, often overlooked details that define a successful season. By choosing the right bung seal and establishing a basic inspection routine, you ensure that every drop of nutrient reaches the soil rather than evaporating into the atmosphere. Invest in the right materials now to protect your resources and your bottom line.