6 Best Sealing Washers For Rainwater Harvesting Systems That Prevent Waste
Prevent leaks and water waste in your rainwater harvesting system. Our guide details the 6 best sealing washers for a secure, efficient, and durable seal.
There’s nothing more frustrating than walking out to your rain barrel on a dry day only to see a dark, damp patch of ground beneath the spigot. That slow, constant drip isn’t just an annoyance; it’s your carefully collected water vanishing into the soil. You’ve lost gallons that could have gone to your tomatoes or filled the chicken waterer, all because of a component that costs less than a dollar.
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Why a Good Washer is Key to a Leak-Free System
The fitting itself—the spigot or the bulkhead—gets all the attention, but the washer does the real work. It’s the flexible barrier that conforms to the slight imperfections between the tank wall and the fitting, creating a watertight seal. Without a quality washer, even the most expensive brass spigot will leak.
Think of the forces at play. A full 55-gallon drum exerts constant pressure on that seal. As the sun beats down, the plastic barrel expands; at night, it contracts. A cheap, stiff plastic or low-grade rubber washer can’t handle that movement. It will develop a "memory," become brittle, and create a tiny gap for water to escape.
That slow drip might seem insignificant, but it adds up fast. A leak of just one drop per second wastes over 3,000 gallons of water a year. Choosing the right washer isn’t just about stopping a nuisance; it’s about respecting the resource you’ve taken the time to collect. It’s the difference between a reliable system and a constant headache.
FarmTek Heavy-Duty EPDM for Long-Term Durability
When you need a "set it and forget it" seal for an outdoor tank, EPDM is the answer. This isn’t the generic black rubber you find in a random assortment pack. EPDM (Ethylene Propylene Diene Monomer) is a synthetic rubber engineered specifically for outdoor exposure. Its primary advantage is its exceptional resistance to UV radiation and ozone.
Your rain barrel lives outside, baking in the summer sun and enduring harsh weather. Materials not designed for this environment will crack and perish within a season or two. EPDM, however, remains flexible and stable for years, maintaining a tight seal through countless cycles of heating and cooling. It’s the same material used for roofing membranes and pond liners for a reason: it lasts.
Look for thick, substantial EPDM gaskets, like those sold by agricultural suppliers like FarmTek. They are designed for the rigors of farm use. Pair one with a quality bulkhead fitting on an IBC tote or plastic drum, and you’ve built a connection that will likely outlast the barrel itself. This is the workhorse washer for 90% of rainwater harvesting setups.
DERNORD Silicone Gasket for Temperature Extremes
Silicone gaskets have a superpower: an incredibly wide temperature range. While EPDM is tough, silicone remains pliable in conditions that would make other materials stiff or mushy. If your system is in a location with dramatic temperature swings—like an uninsulated shed in a northern climate—silicone is an excellent choice. It won’t get brittle and crack during a deep freeze or deform on a scorching hot surface.
This material is also chemically inert and food-grade, making it a great option if you’re concerned about water purity for sensitive plants or animals. The bright white or reddish-orange color of most silicone gaskets makes them easy to spot and inspect.
However, silicone has its tradeoffs. It’s a much softer material than EPDM or neoprene. This softness is great for sealing against slightly uneven surfaces, but it also means the gasket can "squish out" from the fitting if you over-tighten it. You need a gentle touch during installation. Use silicone when temperature resilience is your top priority, not for high-pressure applications where a tougher material is needed.
McMaster-Carr Bonded Seal for High-Pressure Taps
A standard washer can fail when you introduce a pump to your system. The moment a pump kicks on, it creates suction and pressure that can dislodge or bypass a simple gasket. This is where a bonded seal, sometimes called a Dowty washer, becomes essential. It’s an engineered solution for a high-stress problem.
A bonded seal consists of a strong metal outer ring with a trapezoidal ring of rubber vulcanized to its inner edge. When you tighten the fitting, the metal ring prevents you from over-compressing the rubber. It forces the rubber to seal perfectly without being deformed, creating a robust seal that can handle hundreds, if not thousands, of PSI.
You won’t find these at your local hardware store; you’ll need to order them from an industrial supplier like McMaster-Carr. While it may seem like overkill for a rain barrel, use a bonded seal at any connection point on the pressure side of a pump. It’s the definitive way to ensure your pump’s outlet fitting doesn’t become your system’s weakest link.
Hillman Group Neoprene Washer: A Versatile Choice
Sometimes you just need a reliable washer right now. Neoprene is that versatile, readily available option you can find in any hardware store’s specialty fastener aisle. It’s a fantastic general-purpose material that strikes a good balance between durability, flexibility, and chemical resistance.
Neoprene is tougher than silicone and offers better weather resistance than basic nitrile rubber. It will hold up reasonably well to sunlight, though it doesn’t have the extreme UV-proof qualities of EPDM. It’s the perfect choice for overflow fittings, spigots on barrels that are in a shaded spot, or for linking multiple barrels together with low-pressure hosing.
Think of neoprene as the jack-of-all-trades. It may not be the absolute best for any single extreme condition, but it’s good enough for almost any standard application. Its wide availability makes it an indispensable problem-solver to keep on hand for quick repairs.
Banjo Bulkhead Fitting: An All-in-One Solution
Instead of trying to match the perfect washer to a cheap, flimsy fitting, you can solve the problem by starting with a better component. Companies like Banjo specialize in high-quality, glass-reinforced polypropylene fittings designed for agriculture and chemical handling. The key is that they come with a perfectly matched, heavy-duty EPDM gasket.
Buying a complete, high-quality bulkhead fitting assembly eliminates the guesswork. The flange is thick, the threads are precise, and the included gasket is designed to work perfectly with that specific part. You are buying a pre-engineered sealing system, not just a collection of parts you hope will work together.
This is the best approach when you’re setting up a new tank or have had a cheap fitting fail on you. The cost is higher upfront, but it saves you the time and wasted water that comes from a failed seal. When you see the thickness of the fitting wall and the substantial gasket it comes with, you understand you’re paying for reliability.
LASCO Fiber Washers for Traditional Barrel Spigots
If you’re installing a classic, threaded brass spigot into a rain barrel, an old-school fiber washer is often the best tool for the job. These stiff, paper-like washers might not look impressive, but they have a unique property: they swell slightly when they get wet.
This swelling action allows the washer to expand and fill any minor imperfections around the drilled hole, creating an exceptionally tight seal. It’s a "crush and set" type of seal. You tighten the spigot down, and once water hits the washer, it locks everything into place.
The main consideration is that fiber washers are essentially a one-time-use product. If you need to remove the spigot for winter storage or maintenance, you’ll destroy the seal and need a new washer to reinstall it. But for a simple, permanent spigot installation on a standard barrel, their ability to conform and seal is hard to beat.
Proper Installation for a Drip-Proof Connection
The best washer in the world will fail if installed incorrectly. A leak-free connection depends as much on your technique as it does on the material you choose. The most common mistake is over-tightening, which distorts the washer and creates a new path for water to escape.
Follow these simple steps for a perfect seal every time:
- Prepare the surface. After drilling your hole, use a utility knife or a deburring tool to shave off any rough plastic bits from the edge. The surface where the washer will sit must be smooth and flat.
- Position the washer correctly. The washer almost always goes on the flange side of the fitting, which is typically inside the tank. This allows water pressure to help push the washer into the seal, not away from it.
- Tighten with care. Thread the nut on by hand until it’s snug. Then, use a wrench for a final quarter- to half-turn. The goal is to compress the washer just enough to create a seal, not to squeeze the life out of it. You should see the washer bulge slightly, but not get pushed out from under the fitting.
Remember, the washer is doing the sealing, not the force of the threads. Let the material do its job. A gentle but firm touch ensures a connection that will stay dry for years.
That persistent drip from your rain barrel isn’t a problem you have to live with. It’s a sign that a tiny, critical component isn’t up to the task. By taking a moment to choose the right washer for the job—whether it’s a sun-proof EPDM gasket or a high-pressure bonded seal—you’re investing in the reliability of your entire system and ensuring every drop of collected water goes where you need it most.
