Can water get to a tank through the vent?

[seicam]

I have just read this story: http://www.boatus.com/seaworthy/anatomy0710.asp and it got me thinking a bit. On Telstar the outboard engine tanks are in the stern compartment and the whole stern sometime gets underwater if bigger wave comes in from behind. Would it be possible to get water in tanks that way? The tank vent is very small and likely water does not completely flood the compartment, but I thought it's worth asking. Anyone has had a problem like this?

Regards,
Maciek

[Ron]

The story involves a larger boat with fixed and vented fuel tanks. The vents are usually higher up on the hull, and being tossed around like that could get them underwater at times. Depending on the existence and location of any loops in the vent lines, water could back into the fuel tanks. The portable Telstar fuel tanks (I keep two 3 gallon tanks in the locker) have their screw vents on top of the fill cap. You would have to get them underwater to get water inside. But as a precaution, don't open the vents all of the way. Unscrew the vent cap just enough to let air get inside as the fuel leaves.

[Mark]

The fuel compartment on my boat is very wet most of the time. Motoring at full speed (13 kts) with the rudder down causes a water fountain to erupt from the rudder trunk and yes water can and did enter the fuel tank. I fixed it by installing an inline filter and and having the tanks inside garbage bags. I also try to remember to bring the rudder up since it is not need ed motoring anyway.

The big water danger is refilling the tanks from a 5 gal jug in situ in a following sea. On my boat the fuel line was long enough to reposition the tank into the cockpit for heavy weather motoring.

IMO the boat really needs a built in tank with a vent and fill well above the water line.

Mark

[Dan]

I'd point out that Tony installed a fixed tank on his Alaska Edition T28. One of the first things I installed on my boat was a Racor fuel/water separator. I haven't had any fuel related problems on my boat, and think this is mostly due to having the fuel/water filter in place.

As for venting the tanks... I've run a vent line for each tank up into the transom space, where it is very unlikely to get water intrusion. They go to a diverter valve that allows me to close off the vent lines or choose which tank to vent. There is a similar diverter valve for the fuel lines...so all I have to do is switch both at the same time to vent and select which tank I'm running off of.