Fitting non return valve to fuel tank breather

Hi, I am considering fitting a non return valve to the fuel tank breather. Some friends of mine this year racing from Newport to the Lizarad got flattened a number of times and it strikes me a sensible precaution to fit non return valve to stop any possible water getting into the fuel tanks. Any thoughts?  

John B

John, one thought: if you really want to install a non-return valve into a breather, you probably need to install it as close to the hull exit end as possible ... or the assumed knock-down that would cause water to flow into the tank will fill the breather line up to the valve. And you might want to make sure you can easily access and check the valve. Just imagine what happens when that one gets stuck.
Best regards, Martin

John
A non-return valve is not advisable. In addition to expelling air when taking fuel the vent line also needs to supply air, at a much smaller rate though, when the engine sucks fuel from the tank.
If the present vent position is of concern it could probably be improved, high up near the centerline is preferable. The safest system has one vent each side of the boat, but also needs a hose between them just below deck level, and this may be difficult to hide inside.
Kind regards Lars