Fuel tank and water tank vents.

[s/v John Galt]

Can any one tell me where the fuel tank vent goes to? I have a Columbia 41 Center-cockpit with a 100 gallon tank under the starboard side settee. Also, are there any access areas to view/work on the water tank vents? I tried to fill them up and it appears that they are leaking (read gushing when the tank is filled). :cry:

Thanks

S/V John Galt

 

[Peggie Hall HeadMistress]

All tank vents end in vent thru-hulls somewhere on the outside of the boat.

Your water tank vents aren't leaking...when water flows out the vents, it means the tank is full...it's overflowing.

A tank vent has two functions--to provide an escape for air displaced by incoming contents, 'cuz unless air CAN escape, the tank becomes pressurized and cannot be filled any further...and to provide a source of air to replaced contents as they're pulled out...otherwise the pump--fuel pump, water pump, or waste tank pumpout--will pull a vacuum that prevents it from pulling any more out of the tank. This is why it's VERY important to make sure tank vents never become blocked.

So the only thing that's happening in your water tank is, the vent is doing its job...when there's no more room in the tank for water, it's gonna overflow out the vent.

 

[s/v John Galt]

All tank vents end in vent thru-hulls somewhere on the outside of the boat.

Your water tank vents aren't leaking...when water flows out the vents, it means the tank is full...it's overflowing.

A tank vent has two functions--to provide an escape for air displaced by incoming contents, 'cuz unless air CAN escape, the tank becomes pressurized and cannot be filled any further...and to provide a source of air to replaced contents as they're pulled out...otherwise the pump--fuel pump, water pump, or waste tank pumpout--will pull a vacuum that prevents it from pulling any more out of the tank. This is why it's VERY important to make sure tank vents never become blocked.

So the only thing that's happening in your water tank is, the vent is doing its job...when there's no more room in the tank for water, it's gonna overflow out the vent.

Peggie,

Thank you, however I should have been more precise. The tanks are overflowing into the cabin and from under the bulkheads, not through the through-hull fittings as I was watching them very carefully. I know that the vents are supposed to vent to the outside, I was wondering, on the fuel vent, where that was as I can account for all the through-hull vents except for the fuel tank.

s/v John Galt

 

[Peggie Hall HeadMistress]

Oops...

Thought you were a newbie who didn't understand tank vents...but nope...you definitely have a problem...I hope it's only the water tank that's leaking, not the fuel tank.

 

[Alan]

If you had a Fuel Whistle installed you would know exactly where the fuel vent is. The Fuel Whistle is a device installed in the vent line of the fuel tank to signal when the tank is full before spilling into the water. It can also be added to water tank vents for the same purpose. In some locations fresh water is a commodity that can be expensive and not wasted.
Fuel Whistle is available from the "Store" on this site.

http://shop.hunterowners.com/detail.htm?group=766&cat=2618

 

[Old Skool Neil]

A common water tank venting practice for the era of your boat was to run the vent hose up high inside a cabinet and form a 180 degree loop at the top. The rationale was with the vent inside the boat there was no risk of contaminating the water with salt water and the loop on the top of the hose prevented dirt, dust and debris from entering the vent and causing contamination.

Take a hard look inside the cabinets fore and aft of the water tank that go as high as the deck. If it's this type of vent, you'll find it there.

The fuel tank is another matter. No such vent as I described was ever used for fuel. If you're SURE there's a fuel vent leak, it's time to go searching.

 

[Larry Wilson]

Most Columbia fuel vents are on the transom. look for a chrome fitting high and close to center.

 

[s/v John Galt]

My thanks to all who responded. My fuel tank is not leaking, that I know of, the outside of the vent line is cracked and I wanted to replace it. I did find the vent where Larry suggested I look and now just need to measure and run the new vent hose. Alan, your suggestion about the fuel whistle is great and I am going to get one and install it as soon as I get back to Kemah - the boat is in Port Aransas, Tx and I have two weeks to get it ready to move back up to Kemah.

The water tanks vents are another matter as they (2 100 gallon tanks) are custom installed, post-production. I guess I will have to start digging around behind the bulkheads and see if I can find an access port to the space.

Thanks again to everyone for their help.

Mike
s/v John Galt