diesel leak

[Bullfrog]

I've found an annoying leak in my diesel line just where it exits the tank.

 

There's a hexagonal brass fitting that has a stop cock on it and it's just weeping a drop of diesel now and then - enough to make a mess down the engine hole and get mixed up with the bilge water.

 

I've tightened the line out of this fitting successfully, but the fitting itself is still slightly loose in the tank, and if I tighten it, it rotates and the stop-cock ends up fouling the deck-head, and then can't be used.. God knows how they got it on in the first place, perhaps they built the boat around it!

 

My original thoughts were to reseat the fitting using some PTFE tape but I read on here it doesn't work with diesel.

 

Suggestions please.

 

David

[denboy]

it may be that it has been over tightened and crushed the pipe inside the nut and the olive you might have to replace it

[NBMike]

Maybe if you take out the 'working' part of the stopcock it may leave enough room to swing the body of the stopcock around to remove it, allowing you to replace or reseal it. Sorry I don't know what to use , Boss White and hemp ???

Mike

Edited August 7, 2008 by NBMike

[MoominPapa]

I've found an annoying leak in my diesel line just where it exits the tank.

 

There's a hexagonal brass fitting that has a stop cock on it and it's just weeping a drop of diesel now and then - enough to make a mess down the engine hole and get mixed up with the bilge water.

 

I've tightened the line out of this fitting successfully, but the fitting itself is still slightly loose in the tank, and if I tighten it, it rotates and the stop-cock ends up fouling the deck-head, and then can't be used.. God knows how they got it on in the first place, perhaps they built the boat around it!

 

My original thoughts were to reseat the fitting using some PTFE tape but I read on here it doesn't work with diesel.

 

Suggestions please.

 

David

 

In the spirit of recycling, when I asked on here about sealant for diesel, I was recommended this stuff:

clicky

 

Note that this recycled advice is brand new and unused, I've not found the necessary round tuits to actually buy and try this stuff yet. It looks good though.

 

I guess to apply it you would have to drain the tank.

 

MP.

Edited August 7, 2008 by MoominPapa

[Smelly]

I used Rocol white in similar circumstances (ovetightened olive, seepy joint) and it's been fine since.

[Bullfrog]

Thank you all.

 

I will try re-seating with some of the appropriate sealing compound.

 

I shouldn't have to drain the tank 'cos as I said this joint is right under the deck-head and well above the present fuel level.

 

Thanks for your help so far - any more suggestions?

 

David

[Yoda]

Thank you all.

 

I will try re-seating with some of the appropriate sealing compound.

 

I shouldn't have to drain the tank 'cos as I said this joint is right under the deck-head and well above the present fuel level.

 

Thanks for your help so far - any more suggestions?

 

David

 

How is it leaking then?

[Smelly]

How is it leaking then?

 

Shouldn't fuel lines rise from the top 'o' the tank? Hence won't, when the engine's not running, the fuel simply syphon bank into the tank instead of leaking outward? To my understanding that's why...

[Keeping Up]

I wasn ever able to understand the requirement for pipes to leave via the top of the tank. The take-off line, of course, must reach nearly to the bottom of the tank. It makes no difference then whether it exits at that level or rises to the top first; after all, if you were to break the fuel-line at the engine end, the fuel would simply syphon out into the bilges at the same rate as if the pipe had exited at the bottom of the tank.

 

On my own boat, to meet the requirements, the pipe starts at the bottom of the tank, then rises to the top, but instead of exiting at that point it then turns back down to reach the bottom of the tank again before exiting through a skin fitting and tap. I fail to understand how that makes it safer - although I certainly reckon it's safer than having a pipe leaving at the top of the tank where it would be vulnerable to accidental damage. But the boatbuilder and the safety examiner agreed that this was the best way to meet the regulations, so that's what I've got. The return pipe also enters the tank through a skin fitting near the bottom, then also rises to the top of the tank where it finishes.

[smileypete]

I wasn ever able to understand the requirement for pipes to leave via the top of the tank. The take-off line, of course, must reach nearly to the bottom of the tank. It makes no difference then whether it exits at that level or rises to the top first; after all, if you were to break the fuel-line at the engine end, the fuel would simply syphon out into the bilges at the same rate as if the pipe had exited at the bottom of the tank.

 

On my own boat, to meet the requirements, the pipe starts at the bottom of the tank, then rises to the top, but instead of exiting at that point it then turns back down to reach the bottom of the tank again before exiting through a skin fitting and tap. I fail to understand how that makes it safer - although I certainly reckon it's safer than having a pipe leaving at the top of the tank where it would be vulnerable to accidental damage. But the boatbuilder and the safety examiner agreed that this was the best way to meet the regulations, so that's what I've got. The return pipe also enters the tank through a skin fitting near the bottom, then also rises to the top of the tank where it finishes.

 

Hi,

 

Looks like it's advisory for diesel tanks at the current time:

 

Best practice

"We recommend that diesel fuel feed or return lines are drawn

through the top of the tank, or as near to the top of the tank as is

practical"

 

What they could do with stating is why it's advisable to have the exit at the top. Is it to minimise the risk of leakage where the fuel line leaves the tank?

 

On my boat having the pipe leave at the top would make it more vulnerable to damage.

 

cheers,

Pete.

[alan_fincher]

Like many older boats, ours draws off from the bottom of the tank, and has no enforced rise in it.

 

BSS man was entirely happy with this.

 

An obvious advantage David has with his arrangement is he can dismantle the cock, or the feeds to it, with the tank holding plenty of gas oil.

 

Clearly that's not possible without draining the tank, in our case.

[John Orentas]

The idea of requiring all pipes to exit from the top of the tank was to minimise the number of joints and fittings below the level of the fuel but I agree with the others, it's all a bit marginal.. I however did tell my builder not to fit the then compulsory 'Drain plug', just something else to leak.

 

Never heard this about PTFE and diesel before, as far as I am concerned it is the ideal sealing medium for anything and at any temperature, I would not hesitate to use PTFE tape for all diesel fittings, or gas or water or anything you could think of..

 

But you must use plenty of it, that's the mistake some people make, three or four turns is not enough, 10 or 20 is more like it.

Edited August 8, 2008 by John Orentas

[Bigboat]

The idea of requiring all pipes to exit from the top of the tank was to minimise the number of joints and fittings below the level of the fuel but I agree with the others, it's all a bit marginal.. I however did tell my builder not to fit the then compulsory 'Drain plug', just something else to leak.

 

Never heard this about PTFE and diesel before, as far as I am concerned it is the ideal sealing medium for anything and at any temperature, I would not hesitate to use PTFE tape for all diesel fittings, or gas or water or anything you could think of..

 

But you must use plenty of it, that's the mistake some people make, three or four turns is not enough, 10 or 20 is more like it.

 

 

If you want a permanent seal for diesel on a threaded joint use loctite 2701 not cheap but does the job. Do not use PTFE tape it will leak in time.

[Brin Morris]

The idea of requiring all pipes to exit from the top of the tank was to minimise the number of joints and fittings below the level of the fuel but I agree with the others, it's all a bit marginal.. I however did tell my builder not to fit the then compulsory 'Drain plug', just something else to leak.

 

Never heard this about PTFE and diesel before, as far as I am concerned it is the ideal sealing medium for anything and at any temperature, I would not hesitate to use PTFE tape for all diesel fittings, or gas or water or anything you could think of..

 

But you must use plenty of it, that's the mistake some people make, three or four turns is not enough, 10 or 20 is more like it.

 

PTFE tape should not be used on gas fittings as the gas does break down the tape and can cause a leak over time. Although diesel may do the same it will just leak a little and can be fixed without too much of a problem. Using it on gas joints can be a bit more serious.

[Big Steve]

PTFE tape should not be used on gas fittings as the gas does break down the tape and can cause a leak over time. Although diesel may do the same it will just leak a little and can be fixed without too much of a problem. Using it on gas joints can be a bit more serious.

 

So how come you can buy extra thick PTFE tape specifically for gas?

[alan_fincher]

PTFE tape should not be used on gas fittings as the gas does break down the tape and can cause a leak over time.

This is not I believe correct.

 

A PTFE tape is manufactured and marketed explicitly for gas use. I believe it differs from the stuff used for water only by it's thickness. (The gas tape is significantly thicker).

 

If it was going to degrade over time, I don't think respectable firms like BES would b selling it.

 

I don't know the answer for diesel though......

[steelaway]

I've found an annoying leak in my diesel line just where it exits the tank.

 

There's a hexagonal brass fitting that has a stop cock on it and it's just weeping a drop of diesel now and then - enough to make a mess down the engine hole and get mixed up with the bilge water.

 

I've tightened the line out of this fitting successfully, but the fitting itself is still slightly loose in the tank, and if I tighten it, it rotates and the stop-cock ends up fouling the deck-head, and then can't be used.. God knows how they got it on in the first place, perhaps they built the boat around it!

 

My original thoughts were to reseat the fitting using some PTFE tape but I read on here it doesn't work with diesel.

 

Suggestions please.

 

David

 

Hi Dave

It is often the case that the tap lever can be removed to allow the valve to spin.

PTFE works for me.

Alex

[Strads]

Would support Alan Fincher's comment -

 

There are two types ptfe that I know of - i have two reels - white platic spool for water and yellow plastic spool for gas and diesel - states that on the printing -

 

and the advice i was given was as John O's - you need at least 12 plus full wraps round the complete thread! more the merrier rules..

 

I am also sure that there are several other very suitabel compounds - and would reccommend visiting a proper automotive factors -

 

They will have all the commercial used sealants - the ones that professional fitters/ firms use - tell them the use /ie for diesel - heat rangeof the environment etc etc and you will get the correct reccomendation's...

 

 

 

happy plumbing

[Bullfrog]

and yellow plastic spool for gas and diesel - states that on the printing -

 

I now have some of this and also some "jet-lube" jointing compound recommended by a local diesel fitter.

 

When I next get on board and it's not persistently raining I will have a go at fettling the leak and will let you know how I get on.

 

Thank you everybody for all your help so far, brilliant as always.

 

David