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S&S Swan General - Fuel tank (actually water) breather pipe on 41
10 January 2022 - 08:27
Join Date: 01 January 2011
Posts: 36

Fuel tank (actually water) breather pipe on 41

Dear S&S Swan lovers, happy New Year!

Could anyone help me identify please what looks like an in-line valve (maybe?) on Scotch Bonnet's fuel tank breather pipe?

And should it be there and does it require any maintenance or attention?

Many thanks,

Andrew 41/039

10 January 2022 - 09:02
Join Date: 02 January 2008
Posts: 1547

Dear Andrew

This has been discussed earlier, pls see

Kind regards


10 January 2022 - 20:07
Join Date: 01 January 2011
Posts: 36

Dear Lars

thank you for pointing me in that direction, I had missed the previous discussion.

I suspect by now the valve is inoperable but its active function is not currently being missed so I think I shall leave undisturbed for now, but it is good to be aware of its intended use in case of mysterious fuel problems.



11 January 2022 - 04:47
Join Date: 02 January 2008
Posts: 1547


Maybe this is part of the water system? A fuel connection opening into the boat is not allowed.


14 January 2022 - 04:59
Join Date: 01 January 2011
Posts: 36

Dear Lars, thank you for pointing out my mistake so kindly, I was seeing what I expected to see and not what I was looking at, if that makes sense.  I looked today and it is indeed the water tank breather, don't the water tanks breathe through the overflow pipes in the galley sink? And next question, could I trouble you to tell me where the outlet of the fuel breather pipe is? It is the other black pipe in the photo I posted which disappears behind the nav station panelling.

Cheers, Andrew

14 January 2022 - 08:47
Join Date: 05 August 2010
Posts: 162

Dear Andrew,

the tanks breathe through the overflow pipes into the sink. The breather valve is not generally needed, unless there is a section in the pipe that does not follow the continuous upward direction. In that case, there is a "local low" point in the pipe and you will have a water pocket collect in the overflow line, so it cannot breathe (or not easily). The valve is only opened to drain the water pocket after filling the tank, then closed again. I should think it is a manual valve.
From the perspective on your picture, I am not sure if it is needed anyway.

On our 48, the fuel tank vent leads aft into the stern locker. There are two small holes near the stern (on the underside of the overhang) that may have been used for the tank vents, but when we bought the boat, the vents were already branched into the cockpit drains below the cockpit sole, and I have left it that way. I believe you can find the vent exit when you look for openings in the hull (above the waterline, and most likely facing down and/or set close to the waterline) with a tube leading to near deck level on the inside.

Hope that helps,


14 January 2022 - 08:51
Join Date: 02 January 2008
Posts: 1547

Dear Andrew

Martin already answered very well



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