Intalling fuel tank vent question

[bony]

Hi,

Just fitted a new 25 litre S/steel diesel fuel tank to my boat and have arranged it so that I can have a filler neck with locking cap mounted on the deck aft. The tank has a fuel vent hose outlet and I am wondering if there is any restriction on the distance a fuel vent outlet can be mounted from the tank ? I know the vent needs to be higher than the filler neck but in my setup the only was I can achieve that is to mount the vent high up through the backwall of the cabin. This means I'll have a vent hose around 4 metres (about 13ft) long. Is this acceptable?

bony

[Kokanee]

I cannot see why not, as long as there is a constant slope back to tank with no low points.

[GILow]

Originally Posted by Kokanee

I cannot see why not, as long as there is a constant slope back to tank with no low points.

+1.

We had a low point in ours and it kept airlocking till I found it and straightened it out.

[thinwater]

Originally Posted by bony

... I know the vent needs to be higher than the filler neck...

No, it does not. Specifically, if you use a Raycor Lifeguard trap it can be somewhat lower. Many boats have vents below the filler.

It is more important to pick a location where fumes cannot enter the cabin. It smells vile during fueling and there is always a possibility of getting gasoline by accident.

Do make certain the water cannot splash or flow in, even when heeled.

[GordMay]

The fuel tank vent outlet fitting must be located so that overflowing fuel coming out of the vent (at a rate of up to 2 gallons per minute) will not enter the boat.
33 CFR , 183.520 ➥ http://www.law.cornell.edu/cfr/text/33/183.520

[a64pilot]

Is the tank close enough to tie the vent into the existing vent?

[bony]

I will change the vent location to the side of the cabin where there'll be no chance of fumes or leakage into the boat.

Many thanks to everyone for the good advice.

bony

[bony]

Originally Posted by a64pilot

Is the tank close enough to tie the vent into the existing vent?

There was no existing vent in this boat. The original 100 litre tank was not vented and had no outlet to fit one. It never suffered from air or vacuum locks though so air must have been entering the tank thru the filler neck which was a piece of galvanised pipe with a screw cap. It was a shoddy arrangement and that's why I'm replacing the whole system.

bony