New, “no corrosion”, seacocks
Seacocks are a critical component. The failure of a 2 inch seacock one foot below the water line will flood the boat at 300 litres per minute.
The seacocks on Dragon II, which I guess were original and 15 years old, were poor quality and different types of metals were use for the tail pipes making it worse. Read the articles at the bottom of the page for more information.
With advances in design, I went for the reinforced plastic design. You have TrueDesign and Forespar Marlon to choose from. Both produce high quality products using a reinforced engineering plastic (nylon) that will never suffer from corrosion and the valve turns very smoothly.
Quoting from the TrueDesign website:
TruDesign ball valves are designed and made in NewZealand for marine applications above and below the waterline. They comply with ISO 9093-2 and ABYC H-27 and certified by Bureau VERITAS and IMCI.
The body of the ball valve is manufactured in glass-reinforced nylon composite with high impact and tensile strength resulting in a light weight unit, free from corrosion and electrolysis issues. The ball and sealing rings utilise and PTFE polymer to ensure a smooth action and continuous ease of operation over many years. The ball valve is available in both BSP and NPS parallel thread forms and can be locked in the closed position for use on toilet waste outlets.
I chose TrueDesign as the accessories such as tailpipes (to which you attach the hose) came in sizes and configurations that worked for me and Dragon II. Otherwise the two seacock designs seem equally good.
I had a contractor do the work and my major regret is I did not instruct Herman to follow the advice of Nigel Calder and remove some of the balsa core and replace with epoxy before installing the seacocks. Herman assures me that he was diligent with his use and choice of sealant, Sikaflex 291i.
Still…I wish.
Two articles to learn more
https://www.yachtingmonthly.com/news/nightmare-of-seacock-safety-4758
https://www.pbo.co.uk/gear/dezincification-resistant-dzr-skin-fittings-explained-97302
Links to suppliers
TrueDesign website
Forespar Marlon website
A Dragon's Tale 