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Forespar 903018 Marelon 1-1/8" Vented Loop Anti-Siphon Valve

Manufacturer

Forespar

<h3>About Forespar Products Corporation</h3><p><strong>Forespar Products Corporation</strong> has been a cornerstone of the marine industry since its founding in 1966. The company's origin story is as practical as the products it makes: <a href="/7351-forespar">Forespar</a> was started by lifelong boater Robert Foresman simply because he wanted a telescoping whisker pole — and couldn't find one good enough. That hands-on, solve-a-real-problem philosophy has guided every product decision in the decades since, growing Forespar from a single-product idea into a large and diversified supplier of sailing and boating products serving the world market.</p><p>Headquartered in Rancho Santa Margarita, California, Forespar operates a state-of-the-art manufacturing facility that handles the entire product lifecycle in-house. The team uses CAD/CAM design, a full machine shop, plastic injection molding, and carbon composite processing — capabilities that allow Forespar to maintain the tight tolerances and consistent quality that demanding sailors and powerboaters expect. This vertical integration is a key reason the brand has earned such a loyal following across the globe.</p><h3>Marelon&reg;: The Forespar Innovation That Changed Marine Plumbing</h3><p>One of Forespar's most celebrated contributions to boating is <strong>Marelon&reg;</strong>, a proprietary polymer composite formulation engineered specifically for marine plumbing applications. Marelon fittings — including seacocks, thru-hulls, and vented loops — deliver exceptional resistance to corrosion and electrolysis, two of the most persistent threats to below-waterline hardware. Because Marelon components weigh roughly half as much as traditional bronze equivalents, they help reduce overall boat weight without compromising structural integrity. The precision-molded plumbing systems built with Marelon are UL approved and meet A.B.Y.C. standards, giving boaters confidence that their below-deck plumbing is as safe as it is durable.</p><p>Forespar vented loops and thru-hull fittings are trusted by both sailors and powerboat owners who need reliable, maintenance-friendly solutions that hold up in the harshest saltwater environments. The corrosion-free nature of Marelon also means fewer inspections, less maintenance, and longer service life compared to metal alternatives.</p><h3>Sailing Performance Gear: Poles, Vangs, Furling &amp; More</h3><p>Beyond plumbing, Forespar is equally renowned for its performance sailing hardware. The brand's lineup of <strong>spinnaker poles and whisker poles</strong> — available in aluminum, carbon fiber, and composite materials — is designed to help sailors extract maximum downwind performance. The locking telescoping designs allow for quick adjustments on the water, and the carbon fiber options in particular combine a featherlight feel with impressive structural strength. For racers and cruisers alike, Forespar poles represent a genuine upgrade in sail handling capability.</p><p>The <strong>Leisure Furl</strong> in-boom mainsail furling system is another flagship product line bearing the Forespar name — a sophisticated solution for sailors who want easy, reliable sail stowage without sacrificing performance. Rounding out the sailing hardware catalog are boom vangs, sail handling hardware, davit systems, and safety equipment, making Forespar a one-stop source for outfitting a sailboat from deck to transom.</p><h3>Powerboat &amp; Cruising Accessories</h3><p>Forespar's reach extends well beyond racing sailboats. The brand's <strong>davit systems</strong> and the innovative <strong>Nova Lift</strong> make deploying and retrieving dinghies, tenders, and outboard motors significantly easier for cruising families and liveaboards. Forespar's marine lighting products offer dependable illumination for navigation and on-deck use. The Flopper Stopper — a uniquely Forespar solution — helps reduce uncomfortable rolling at anchor, a quality-of-life upgrade that any offshore cruiser will appreciate.</p><p>Whether you're racing offshore, cruising coastal waters, or maintaining a powerboat at the dock, Forespar has built products specifically for your challenges. The brand's commitment to innovation, quality manufacturing, and real-world boating experience has made it one of the most trusted names on the water for more than five decades.</p>

Part Number

903018
06/02/2036 5:56 PM
Sale Price

$38.16

In Stock (10+)

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Usually delivered within 2 days

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No Hassle Returns

No Hassle Returns

Live-in-stock inventory

Live-in-stock inventory

Fitment guaranteed

Fitment guaranteed

Product Details

The Forespar 903018 Marelon Vented Loop is a vital safety component for any marine plumbing system, designed to prevent dangerous back-siphoning that could lead to flooding or sinking. This 1-1/8" vented loop is constructed from glass-reinforced Marelon composite material, offering superior corrosion resistance compared to traditional bronze fittings.

Key Features:

  • 1-1/8" thread size for secure connection to marine plumbing systems
  • Glass-reinforced Marelon composite construction resists corrosion and electrolysis
  • Vented design allows air to enter the line, preventing back-siphon effect
  • Lighter weight than bronze alternatives while maintaining strength
  • Suitable for use above the waterline in head, galley, and engine cooling systems
  • Will not deteriorate or corrode in saltwater environments

Vented loops work by creating an air break in the plumbing line when fluid flow stops, preventing water from being siphoned back into the boat. This is especially critical for marine sanitation systems and any through-hull connections below the waterline. The Marelon material offers exceptional durability and longevity in harsh marine environments without the risk of galvanic corrosion.

Products specifications

Dimensions

1 1/8"

Material

Marelon

Type

Vented Loops

Good experience, however, I was hoping that 'FREE SHIPPING' would be the standard for Autoplicity.

quick and easy, like it should be.........

Would really like these to be delivered by Friday!

Thanks

Great so far

Easy to find product and to check out.

great price and service

Very easy and best price

There.was a bit of miscommunication between sales and shipping departments, but my order was filled and shipped as stated. Very low price, in fact the lowest on the net, and I did alot of research. Other than the shipping issue, I'm very satisfied and will buy more parts from them soon. Thank you!!!

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