Seacock problems

[Guest]

Why do we use seacocks – especially on cockpit drains? These are never turned off! What PRECISELY is wrong with plastic skin fittings, good quality hose and two s.s. jubilee clips? OK hose replacement is a problem but not a major one.

To immerse the traditional bronze gate valve in warm seawater (my boat in Med) and expect it to work indefinitely seems hopelessly optimistic. Typical problems: 1. They don’t shut-off – even new ones allow a trickle through. 2. They seize-up - especially when trying to stop the trickle! 3. The shaft can leek. 4. Inlet and outlet threads can leek 5. Worst of all is the potential risk of electrolytic corrosion (why oh why is there not a small set screw for a good electrical connection instead of struggling with copper pipe clamps?) Just a trickle will sink a boat if left for weeks so what is the point of a valve that doesn’t fully shut off?

Ball valves look more effective as a shut-off device but does that polished ball corrode and are they made of bronze like gate valves?

The regular replacement of seacocks always seems to involve hacksawing through the skin fitting and replacing the lot. This requires a midget Houdini to hang upside down for several hours and I’m getting too old!

 

[spark]

"Why do we use seacocks ...?"

If the hose ruptures or the clips fail the sea-cock is there to stop the Med from getting where you don't want it to be.

Gate valves are not recommended for sea-cock duty (because they don't always shut off properly and are prone to thread failure)

Ball valves are much better (bronze or Marelon) but still need to be turned regularly to keep them in working order.

 

[Oldhand]

Had a boat with Marelon ball valve seacocks for 10 plus years and had no problems at all, thus would recommend you replace your gate-valves with same.

 

[extravert]

Here is a good article on what is wrong with plastic skin fittings that are anywhere near the water line. Good picture half way down.

<A target="_blank" HREF=http://www.yachtsurvey.com/sinking.htm>http://www.yachtsurvey.com/sinking.htm</A>

 

[dickh]

Why do we use seacocks? If your drains are under water you need a seacock fitted to turn it off if you have a hose problem (or need to replace the hose...)
Plastic fittings - DO NOT USE BELOW THE WATERLINE!!! They are nowhere as strong as metal, suffer badly from UV, can break when overtightened over time, can melt in a fire. Plastic should only be used well above the waterline.
Gate valves again, should not be used - as you have found out - they LEAK eventually(I assume you have gate valves). Only use proper Blake type seacocks, bronze ball vales or the Marelon plastic type(reinforced plastic - approved in the US)
Ball valves are fine as long as you get BRONZE ones - there are a lot of brass ones around - only problem is they all seem to have painted steel handles which rust!.
Blake seacocks are very good, tapered cone type, never leak if properly ground in, but are expensive(about £85 for 1¾" bore).
Seacocks should last for several years and not need replacing regularly - it looks like you have 'cheap' gate valves - replace them and you won't have any further problems.
Goood Luck.


dickh
I'd rather be sailing... /forums/images/icons/smile.gif