Ball Valve

Forespar® MF 850 series of Ball Valves are precision moulded in Marelon®.

Great strength, light weight, easy installation and maintenance as well as freedom from corrosion and electrolysis creates the ideal valve for controlling inlet and outlet water flow above and below the waterline.

The operating temperature range of Marelon® is -40° F to +176°   (-40°c to +80°c), making the valves reliable in every climate and season.  

Marelon® Valves and Fittings
Almost all Marelon® valves, thru-hulls and fittings use NPSM parallel thread forms that require thread compound or Teflon® tape to seal. There are two exceptions to using parallel threads in Marelon®. Forespar's Marelon® “93 Series” plumbing system comes standard with buttress threaded thru-hulls that mate to buttress threaded valves. And Forespar Marelon® “HC Series” line of reducing tailpipes all employ true NPT tapered threads.

British vs United States Parallel Thread Standards

The American NPSM parallel thread standard has a thread flank angle of 60°. The British Standard Pipe, or BSP standard for parallel threads has a thread flank angle of 55°. Identification can also be made by inspecting the root and crest of the threads. The truncation of the root and crest of American standard threads are flat. The truncation of the root and crest of British standard threads are round. 

For more information on Forespar's marine plumbing go to our Buying Guides.

Valve Maintenance: All Forespar Valves are non-corrosive, but like any moving part in a marine environment they require regular inspection and lubrication. Do not fail to actuate the handle and lubricate the seals on a regular schedule.



Related Content


What is MareLube TEF 45?

The ultimate in corrosion protection. Protects, lubricates, stops corrosion, prevents seizing and galling. Won't wash away in fresh or salt water or detergents.

Read more


Forespar®Plumbing

Forespar® Plumbing is made of Marelon® a superior marine-grade product.

Read more


Know Your Thread Forms

MARINE thru-hulls, tailpipes, valves and seacocks have parallel threads known as “American Standard Straight Mechanical” pipe threads or “NPSM”. These require thread compound or Teflon tape to seal.

Read more


Marelon® - Marine Grade Plumbing Systems

In the late 1970’s we (Forespar) undertook a search for a material that could replace the traditional bronze plumbing components used in boats.

Read more