Diesel tank air vent

[zoidberg]

I'm repositioning an existing diesel fuel tank air vent. Originally, this lengthy plstic tube terminated to air via a mesh-screened 'nipple' protruding 3/4 inch from the rear deck - where from time to time it would likely be swamped by solid water.

I could mount it up inside the hollow grp stern coaming, on/crossing the centreline. But, would I be better keeping it all inside the stern locker 'upstand' - or protruding as before, but about 3-4 inches higher?

Thoughts?

 

[snowbird30ds]

It's an overflow as well as a vent so it should go overboard, take it as high as you can then back down to the screened fitting to stop water getting in.

 

[Refueler]

The trick is to put an inverted U in the pipe before exiting ...

If you can get to the pipe internally - you can add a length to create the U .... no need to replace the whole... and you can still use the existing fitting.

 

[thinwater]

The trick is to put an inverted U in the pipe before exiting ...

If you can get to the pipe internally - you can add a length to create the U .... no need to replace the whole... and you can still use the existing fitting.

We need a picture.

Was the vent vertical on a deck? I doubt that, as rain would go into the tank.

Was it on the transom? You could use a U, as Refueler suggested, but it must be high enough to prevent impact pressure from driving the water over it, and it must self-drain overboard.

(This type of transom vent has internal baffles to kill the velocity and a built-in U to resist slap. Common on powerboats. $25.)


I would NOT terminate it anywhere inboard. Reasons given.

 

[Plum]

The trick is to put an inverted U in the pipe before exiting ...

If you can get to the pipe internally - you can add a length to create the U .... no need to replace the whole... and you can still use the existing fitting.

Yes, that is what I have. The loop goes up to nearly the height of the coach roof , significant higher than the filler, then down to the gauze fitting which is under the side deck, not overboard. Has never leaked any fuel into the boat after 30 years of sailing.

 

[Neeves]

Yes, that is what I have. The loop goes up to nearly the height of the coach roof , significant higher than the filler, then down to the gauze fitting which is under the side deck, not overboard. Has never leaked any fuel into the boat after 30 years of sailing.

We had a 10mm tube connected to the bottom of the tank, attached to a bulkhead parallel to the tank (vertically), with a tap at the top, usually left open, and terminated well above the top of the tank. The tube gave the fuel level, marked in 20l intervals, 200l tank.

the filler point, tube, tank and tap were all adjacent to each other and you knew exactly when the tank was full.

Our tank was fibreglass, and moulded to fit three sides round the mast support (centralising weight). The tank was in a locker with no access to the accomodation.

Jonathan

 

[Refueler]

We had a 10mm tube connected to the bottom of the tank, attached to a bulkhead parallel to the tank (vertically), with a tap at the top, usually left open, and terminated well above the top of the tank. The tube gave the fuel level, marked in 20l intervals, 200l tank.

the filler point, tube, tank and tap were all adjacent to each other and you knew exactly when the tank was full.

Our tank was fibreglass, and moulded to fit three sides round the mast support (centralising weight). The tank was in a locker with no access to the accomodation.

Jonathan

mmmmm what has that to do with OP's question ?

 

[lustyd]

It's an overflow as well as a vent so it should go overboard

Arguably that says it should go inboard so that you can clean up your diesel spill rather than pollute the sea. I realise that’s the traditional answer but it’s not a good one.

 

[Neeves]

mmmmm what has that to do with OP's question ?

Our was an overflow, a vent and means to measure fuel volume in the tank, all contained in a locker. Open the locker lid and you can access the file inlet and monitor the refilling of the tank. As long as the locker is isolated from the accomodation you don't need the a device out in the open, just a simple transparent pipe. You could spend money on thinwater's answer (but you would need a fuel gauge), Zoidberg is considering a simple pipe, internal to the locker and external to the tank held in the locker) - just as we had - and for 25 years it was faultless. Our fuel cap was a vent, belt and braces.

It might have no application to Zoidberg's question but we did not merit a photograph so had to guess.

Now what did you suggest....?

Jonathan

 

[Refueler]

Our was an overflow, a vent and means to measure fuel volume in the tank, all contained in a locker. Open the locker lid and you can access the file inlet and monitor the refilling of the tank. As long as the locker is isolated from the accomodation you don't need the a device out in the open, just a simple transparent pipe. You could spend money on thinwater's answer (but you would need a fuel gauge), Zoidberg is considering a simple pipe, internal to the locker and external to the tank held in the locker) - just as we had - and for 25 years it was faultless. Our fuel cap was a vent, belt and braces.

It might have no application to Zoidberg's question but we did not merit a photograph so had to guess.

Now what did you suggest....?

Jonathan

Post #3 ....

OP is asking based on his worry that solid water may enter the vent .... reasonable concern. His query goes on to ask if moving it to inside a locker ...

But all based on reducing risk of water entering the tank.

My post #3 gives a quick simple solution that needs no move of vent .. no drilling any other holes ... just a simple extra length of pipe added to give the inverted U which will solve the matter ....

As regards overflow - I assume like most boats - his filler point is on deck or external - so any overflow will not be contained in locker ... and means that moving his vent will not solve that matter ...

 

[lustyd]

As regards overflow - I assume like most boats - his filler point is on deck or external - so any overflow will not be contained in locker ... and means that moving his vent will not solve that matter ...

The filler is usually above the vent, so the vent will purge first on almost all boats. Fuel pumps should cut off if the filler fills.