Marelon Pipe to Hose Adapters
What Are Marelon Pipe to Hose Adapters?
Marelon pipe to hose adapters — sometimes called tailpipes — are specialized marine plumbing fittings designed to create a secure, leak-free connection between threaded pipe fittings and flexible hose lines aboard a boat. Also known as tailpipes, they are an ideal choice for joining hose lines to ball valves and seacocks. Whether you're routing engine cooling water, bilge drainage, or any other fluid system on your vessel, these adapters are a critical link in keeping everything connected and watertight.
Why Marelon? The Material That Changed Marine Plumbing
Marelon is not ordinary plastic. Rather than actual plastic, Marelon is a polymer composite (glass-reinforced DuPont Zytel to be exact) — much tougher stuff, which is why these fittings have long since been accepted by the ABYC and certified by the ISO as meeting or exceeding the required mechanical properties for use on boats.
In the late 1970s, engineers undertook a search for a material that could replace the traditional bronze plumbing components used in boats, as the frequency of severe and often catastrophic corrosion and the problem of conductivity in bronze had long been a source of frustration for yacht designers and boat builders. The result was Marelon — a proprietary composite that offers a compelling list of advantages over metal:
- Zero corrosion & no electrolysis: Marelon fittings are totally resistant to deterioration caused by stray current or galvanic corrosion.
- Exceptional strength: Among plastic fittings, Marelon is more than twice as strong as nylon, its next closest rival.
- Lightweight: Marelon is less than half the weight of comparable bronze fittings, UV stabilized, and will not support combustion — making it a logical choice for today's modern composite hull forms.
- Industry certified: Marelon products are known for their corrosion resistance and compliance with ABYC and ISO standards.
- Easy installation: Marelon fittings can be installed using the same techniques and materials as bronze fittings.
Key Considerations When Shopping Marelon Pipe to Hose Adapters
Before selecting an adapter, it's important to understand thread types. Forespar threaded plumbing fittings, like most true marine plumbing fittings, use NPSM threads (National Standard Free-Fitting Straight Mechanical Pipe Thread). NPT (National Pipe Threads) are tapered, while NPSM threads are parallel — the two types are not designed to work together. Always confirm your existing valve or seacock thread type before purchasing. Adapters with NPSM parallel thread form require thread compound or Teflon® tape to seal properly.
Also pay close attention to sizing: hose size refers to the barbed end of the adapter, while pipe size refers to the threaded end. Having the right combination ensures a snug, reliable fit that resists loosening under vibration and pressure.
The Leading Brand: Forespar
Forespar's Marelon glass-reinforced composite polymer plumbing systems have been the #1 trusted alternative to the older, heavier, more expensive, and corrosion-prone bronze for over 35 years. Over 300 boat builders worldwide have some type of Marelon product already in use in their designs. Forespar Marelon pipe to hose adapters are available in a range of sizes and thread configurations — including both male and female ends — to suit virtually any marine plumbing layout above or below the waterline.