Diesel Tank Vent

[Jabs]

The diesel tank on my Contessa 26 fills through the aft deck. I currently have a vent into the rear locker.

The end result is that with a full tank and a rough sea, there is a constant smell of diesel on the boat.

Does anyone have any bright ideas on a good way to vent the tank and avoid smells?

The boat is quite small hence tends to get wet! I can't really see having an external vent if I am to avoid water getting in.

Thanks

Tony.

 

[Evadne]

I have a similar boat and have had a similar problem. My current vent is a swan neck cunningly fashioned from copper tube that sits just aft of the coaming, with the mouth an inch above the deck. But am thinking of replacing this with a purpose made item from Timage here. We have similar freeboard to you and have never had seawater in the tank.

 

[rob2]

You might like to consider gaining some height by taking the vent pipe up inside the pushpit tubing, or any other vertical tubes you have attached. Having sailed many times on a Co26, I know how wet it can get - never popular with the skipper when I caught a wave in the mainsail and dumped it on top of him! A lot depends on the design and layout of the tank and filler, unless the tank is baffled, fuel will slosh up the filler and vent especially if there is little height to them.

Rob.

 

[theoldsalt]

Fitting a non-return/check valve in the vent will let air in but not let diesel out. The disadvantage will be that filling the tank will be slower as air will have to escape through the filler tube.

http://www.thinkauto.com/onewayvalves.htm

Plenty available if you Google

 

[vyv_cox]

Why not fit a standard vent? Many chandleries sell them, here are some http://www.asap-supplies.com/marine/tank-vents There are two on my boat, one for fresh water, one for fuel.

 

[theoldsalt]

Vyv,

Do these standard vents as supplied by ASAP have check valves fitted? If not, how do they prevent spillage in rough weather and the smell of diesel escaping, which is what, I think, Japs was looking for.

 

[vyv_cox]

Vyv,

Do these standard vents as supplied by ASAP have check valves fitted? If not, how do they prevent spillage in rough weather and the smell of diesel escaping, which is what, I think, Japs was looking for.

Not as far as I know, but my vent is slightly lower than the filler, which has a hose neck to the tank about 4 inches long. The vent is in line fore-and-aft with the filler. I have never seen any leakage but as the vent is outside the boat the smell is unlikely to be a problem. It helps to route the hose upwards from the tank to the height of the filler before descending to the vent.

 

[prv]

Do these standard vents as supplied by ASAP have check valves fitted?

Mine doesn't, and it looks to be the same as what ASAP have.

If not, how do they prevent spillage in rough weather and the smell of diesel escaping, which is what, I think, Japs was looking for.

They're meant to be mounted outside, so escaping smells are no problem. A little spillage in rough conditions with a very full tank is not ideal, but better outside than in the locker. Mine's mounted two feet above the tank so shouldn't spill, though the OP may not have the height available.

The real question is whether they stop water getting in, not diesel getting out. I assume mine won't, but it's mounted facing downwards on the outside of the after cockpit coaming next to the mizzen mast - a pretty sheltered position that ought to stay dry short of complete inversion.

Pete

 

[Poignard]

I have a similar boat and have had a similar problem. My current vent is a swan neck cunningly fashioned from copper tube that sits just aft of the coaming, with the mouth an inch above the deck. . . . We have similar freeboard to you and have never had seawater in the tank.

That's what I have. Easily home-made from a length of 15mm copper pipe and two solder-ring elbows.

 

[fisherman]

A local boatbuilder fits tank vents both sides and crossed over, in 15mm copper, fitted to rise gently along its length, so any fuel sloshing up is drained back to the tank.
So, when the boat rolls or is heeled the lower end of the tank is vented up to the high side, with a swan neck above deck. If you had twin tanks the higher one whose vent is below water due to excessive heel or weather might draw water if fuel is being drawn which could drain into the tank when the boat righted. Personally if I thought that would be a problem I would fit a float valve on the end, like the ping pong ball in a snorkel type, or just fit the vent below deck.