Fuel is leaking from tank ventilation tubes

[Berke]

Hi all;

I have motorsailer and when my tanks are full and the boat is heeling on either of the sides; fuel is leaking from ventilation tubes of the fuel tanks. Is there a practical way to eliminate that? I plan to install a simple valve and close the ventilation tubes while sailing but it doesnt sound propoer to me. I also dont prefer to make tubes longer.

[Cheechako]

You mean leaking into the boat or into the water? If you close the valves you will develop a vacuum and the engine will quit.... if running. You could try looping the vent tube up above the vent fitting.

[Sailmonkey]

vent your starboard tank out to port and your port tank out to starboard if possible. this will guarantee your tank vents will be higher than your tanks when sailing.

[HappyMdRSailor]

Originally Posted by Sailmonkey

vent your starboard tank out to port and your port tank out to starboard if possible. this will guarantee your tank vents will be higher than your tanks when sailing.

+1... Such a smart monkey!!!

[lorenzo b]

Your tanks should not be filled to the top, leave at least 10% empty. When you are under power, make sure the fuel return line goes to either both tanks or the tank you are drawing from, or you will flood the other tank.
For now, put some of your fuel in cans until you need it.

[delmarrey]

Originally Posted by Cheechako

You mean leaking into the boat or into the water? If you close the valves you will develop a vacuum and the engine will quit.... if running. You could try looping the vent tube up above the vent fitting.

Agreed!
A loop too is also good for keeping out water, especially when washing down the boat with a hose. But also your vent fitting should as high as possible. On ships they run a stand pipe, with a loop at the top, up on deck. One could do the same by installing a deck fitting and run a looped hose up a stanchion, or ?

[delmarrey]

Originally Posted by Sailmonkey

vent your starboard tank out to port and your port tank out to starboard if possible. this will guarantee your tank vents will be higher than your tanks when sailing.

Yeah, if the vent fitting is on the outboard side of the tanks. Otherwise, it wouldn't make any difference.

[Panope]

Originally Posted by delmarrey

Agreed!
A loop too is also good for keeping out water, especially when washing down the boat with a hose. But also your vent fitting should as high as possible. On ships they run a stand pipe, with a loop at the top, up on deck. One could do the same by installing a deck fitting and run a looped hose up a stanchion, or ?

Fuel vent is just above the upper starboard door hinge. One vent for both Port and Starboard tanks. Works good.

Steve

[transmitterdan]

Originally Posted by delmarrey

Yeah, if the vent fitting is on the outboard side of the tanks. Otherwise, it wouldn't make any difference.

I don't understand this comment. Vent fittings should be on top of the tank, not on the side. What manufacturer puts vent fittings into the sides of fuel tanks?

[Berke]

Fuel is leaking on the deck, ventilation tubes are as high as the bulwarks. so making them longer will look quite ugly. opposite side ventilation idea by Sailmonkey is quite interesting. that might work as I have a lot space in the engine room where tanks are located so extra piping may work, though they need to go above engine which may create some heating issues for those plastic tubes.
do you know if any valve that may let air into the tanks but not letting fuel go out?
I have two tanks and they are connected, one idea I have is to close their link when the tanks are full, so to lessen the pressure coming from opposite side tank to the heeling side. but this will also require a lot manual job.

[transmitterdan]

Originally Posted by Berke

Fuel is leaking on the deck, ventilation tubes are as high as the bulwarks. so making them longer will look quite ugly. opposite side ventilation idea by Sailmonkey is quite interesting. that might work as I have a lot space in the engine room where tanks are located so extra piping may work, though they need to go above engine which may create some heating issues for those plastic tubes.
do you know if any valve that may let air into the tanks but not letting fuel go out?
I have two tanks and they are connected, one idea I have is to close their link when the tanks are full, so to lessen the pressure coming from opposite side tank to the heeling side. but this will also require a lot manual job.

I think that could be your problem. The fuel from the high side tank is forcing it out of the low side tank. Opposite side ventilation will not help this case. It sounds like the previous owner did not understand how diesel tanks work. In dual tank installations there should be valves before the Y connection where the tanks are connected together. Same is true for the fuel return. Then you only open the 2 valves associated with one tank at a time. Then heel should not cause a problem. Plus you can transfer fuel from one tank to the other by opening the opposite return line valve for a short period of time.

Can you insert 4 manual ball valves where the fuel supply and return lines join together?

[S/V Alchemy]

Originally Posted by Panope

Fuel vent is just above the upper starboard door hinge. One vent for both Port and Starboard tanks. Works good.

Steve

So if you do have a leak, you lubricate the hinges? Genius!

Actually, if you fabricated that companionway yourself, I am very impressed. I am having very little luck finding a local aluminum fabricator and none of the "pros" out your way seem to want the job: too small.

By the way, North Sea trawlers, which do a lot of heeling, sometimes have the tanks vent to a gooseneck fitting high on the sides of their pilothouses.

[Panope]

Originally Posted by S/V Alchemy

So if you do have a leak, you lubricate the hinges? Genius!

Actually, if you fabricated that companionway yourself, I am very impressed. I am having very little luck finding a local aluminum fabricator and none of the "pros" out your way seem to want the job: too small.

By the way, North Sea trawlers, which do a lot of heeling, sometimes have the tanks vent to a gooseneck fitting high on the sides of their pilothouses.

I had not thought of the self lubricating hinge aspect - so no genius here. If fact, the Port side hinge has the raw water intake loop vent above it - so a leak there "lubricates" the hinge with salt water!

I will take the credit for building the companionway (and everything else above deck).

Steve

[Sailmonkey]

Originally Posted by Berke

Fuel is leaking on the deck, ventilation tubes are as high as the bulwarks. so making them longer will look quite ugly. opposite side ventilation idea by Sailmonkey is quite interesting. that might work as I have a lot space in the engine room where tanks are located so extra piping may work, though they need to go above engine which may create some heating issues for those plastic tubes.
do you know if any valve that may let air into the tanks but not letting fuel go out?
I have two tanks and they are connected, one idea I have is to close their link when the tanks are full, so to lessen the pressure coming from opposite side tank to the heeling side. but this will also require a lot manual job.

This will help

Lifeguard LG100 Fuel/Air Separator - Racor | Fisheries Supply

But you really need to remove the cross connection on the tanks. If you vent out opposite sides, and the tanks are not cross connected you'll probably no longer have a problem. I would build a manifold for fuel supply and return that is accessible from somewhere easy to access.

[Berke]

thank you all. i will try to find that seperator in Turkey; though it wouldn't be easy.
There are valves in between tanks and I will try cutting the link when tanks are full.