fuel tank drain plug

[Boat&Bikes]

My diesel tank has a bottom drain point with a blank plug screwed into it.I would like to fit a drain tube to it so i can drain off any water that settles at the tanks bottom.My question is,and im hoping someone has experience of this is if i unscrew the plug currently in it, will it be an issue to screw in a new fitting complete with a tap? I am concerned the pressure of escaping diesel will stop me being able to screw the new fitment in? The tank is pretty full at the moment.

 

Cheers,

 

 

Ian.

[alan_fincher]

I think the problem will be if it is is some kind of taper fitting that you will need to use something to seal that fitting.

 

Obviously that rules out a number of thread-sealing possibilities if you are going to attempt to screw it in against rapidly escaping diesel, and my immediate reaction is that about your only hope of getting it sealed up again might be PTFE tape.

 

I don't think I'd try it though, as I suspect it will jet a very long way until you can get something back in the hole, and spew everywhere whilst you are making the initial turns of the screw, (assuming you can ).

 

Diesel seems to search out the tiniest spaces and leak very successfully through joints that would normally not leak with other fluids like water and oil. I think you could end up with a real risk of it leaking when you have done it.

 

I have not checked BSS regulations. Do they allow a tap which, if you open it, without catching the contents, will let diesel run into the boat? Perhaps it's OK if that tap normally has its own cap on the end too? But check, if you haven't if there are any restrictions to what you can do.

[sharpness]

I dont think the pressure would stop you screwing it in but you will have one hell of a mess if you dont get it in cleanly first time. If it doesnt seal properly & you need to take it out again you'll have it all over again.

Run the tank down really low, pump the rest out into a jerry can first.

While you are at it I seem to remember from somewhere that you cant have just a plain tap as a drain, it must have a cap to stop it being drained accidently. I cant remeber where I got that from, is it covered in the BSS regs?

 

Steve

 

 

Snap

Edited November 21, 2012 by sharpness

[Ray]

This may be a complete non starter, and a load of rubbish, but . . . .

 

If I turn off my water pump, drain the residue through one tap to eliminate the pressure and then make sure all taps are closed I can open the drain on the cold and little water escapes. That's how I've done some modifications to the pumping runs without draining the water tank.

 

If you seal the vent on the oil tank temporarily, make sure the filler cap is air tight and have any other connections to the tank closed (and sealed), how much diesel would escape then?

[alan_fincher]

If you seal the vent on the oil tank temporarily, make sure the filler cap is air tight and have any other connections to the tank closed (and sealed), how much diesel would escape then?

I don't know - but would you fancy trying it.....

 

..... with diesel!

[RLWP]

Is the fuel tank drain fitted with a plug or cap that can only be

removed with tools?

 

Section 2.8.1/R R means it is a requirement

 

http://www.boatsafetyscheme.org/media/164488/bss%20guide%20chap2.pdf

 

Richard

Edited November 21, 2012 by RLWP

[onionbargee]

You need a lockable ball valve for a start, you just don't want to have that valve accidentially open. If you try to do a hot swap, you may find you can't find the first threads, and then your swimming in diesel, plus you don't know if its BSP parralel or taper. It will be simple to drain the tank into a couple of 25 L containers, and you can also clean out the sludge at the same time. Then you can properly seal the treads with PTFE tape (gas grade only, not plumbing grade )

 

good luck.

[Boat&Bikes]

The fitting i have prepared has both a tap and a threaded end to screw a blank into,i believe this to be safe and ok for the safety certificate.I am though in two minds about attempting the change due to the possibility of having many gallons of diesel in my bilge.....God knows why someone went to the trouble of drilling and tapping the tank then blanking it off.

[alan_fincher]

While you are at it I seem to remember from somewhere that you cant have just a plain tap as a drain, it must have a cap to stop it being drained accidently. I cant remeber where I got that from, is it covered in the BSS regs?

 

Steve

 

Snap

We are correct on that.....

 

2.8.1 REQUIREMENT

 

Is the fuel tank drain fitted with a plug or cap that can only be removed with tools?

 

Check each fuel tank for the presence of a fuel drain facility.

 

If fitted, check the drain outlet for the presence of a plug, cap or blank.

 

If present, the outlets from fuel tank drains and drain valves must be terminated with a ‘tools-to-remove’ plug, cap or blank.

 

EDIT: I see Richard has posted a link.

Edited November 21, 2012 by alan_fincher

[Ray]

I don't know - but would you fancy trying it.....

 

..... with diesel!

 

It might be worth a careful punt to start with. Loosening the blank plug carefully and slowly. From memory I think I got less than an egg cup full from my water system so I presume the same would apply in this instance. If the flow from the loosened plug didn't stop after that amount then tighten plug again and try another option.

 

However, as others have said, it is an excellent opportunity to clean the tank out if the tank is pumped dry first. We filled a 25 litre container with part of the content of the charity boat's fuel tank. A good 4 to 5 litres of that was crud from the bottom of the tank of a boat that isn't even 5 years old yet!

[alan_fincher]

It might be worth a careful punt to start with. Loosening the blank plug carefully and slowly. From memory I think I got less than an egg cup full from my water system so I presume the same would apply in this instance. If the flow from the loosened plug didn't stop after that amount then tighten plug again and try another option.

..... and hope that whatever was sealing it fully before is still in good enough condition to do so again as you tighten it back up.

 

I tend to drive these decisions on whether anybody I think I can trust has already actually tried something, and got away with it.

 

If someone comes on, and says they have managed to change the drain plug at the bottom of a diesel tank over to some other thing screwed in, then I might be prepared to give it a cautious punt.

 

Until they do, knowing just how unpleasant diesel over everthing is, I'm not sure I'd be up for cautious experimentation.

 

.........And I'm the sort of person known in my past life to have knowingly drawn the prop shaft out of a floating boat!......

[ditchcrawler]

I have visions of you with diesel from chin to foot dripping off your lap, your finger in the hole with diesel running up your area to your elbow and both the new valve and old plug are somewhere out of reach in the bilge.

[CV32]

It should be possible - early summer i foolishly filled our tank to full (250 litres) for the first time as I was changing fuel filters and had read about having a full tank to reduce any chance of air locks.

 

It started to leak at the isolate tap at the base of the tank ! Sam Matts visited and saved me from watching all 250 litres ending up in the engine hole ... Sam clearly had previous experience of changing stop taps on tanks and made it look easy - i would have had considerably more in the engine hole.

[bizzard]

It should be possible to do this without too much spillage. The tap ideally needs to go on first, directly onto whatever the threaded stub on the tank is, probably a bit of BSP taper threaded pipe welded on. First of all you need to know what size and thread type this is so as to have the correctly threaded tap at hand. The next thing to make sure of is ''is there enough clearance below this stub to be able to screw the tap on, or is it too close to perhaps the uxter plate''.

Choose a tap with a direct straight through passage when open like a tapered plug cock tap, i have an ordinary Wade gas tapered plug cock tap on mine.

Find a nice slim sharpened pencil which will pass right through the plug cock when open.

Tape off around tank breather with insulation tape, this might help slow the flow from the tank a little by vacuum.

Place a shallow dish under the drain stub, undo the blanking cap and bung the pipe hole smartly by poking and tapping in gently the pencils tapered end into the drain stub.

You can now clean up the stub fitting and apply a sealant of your choice.

And then very carefully with the lever set to the open position, usually ''inline with the tap body'' slide the plug-cock tap over the pencil and screw it up tight positioning it with the operating lever in a convenient position.

Now as quick as lightening pull out the pencil and turn the tap off. Fit an end blanking cap to the this tap ''the law'' until your ready to fix the extension pipe ''which will also need an end blanking cap'', which you can now do at your leisure. Remove the tape from the breather. That's about it. If you have the gear at hand and don't fumble the job will be done with very little fuel spillage. Hope this helps.

[onionbargee]

A ball valve with the handle taken off can only be opened with " tools" ie a handle, (same as an acetelene cylinder )

[David Mack]

My diesel tank has a bottom drain point with a blank plug screwed into it.I would like to fit a drain tube to it so i can drain off any water that settles at the tanks bottom.My question is,and im hoping someone has experience of this is if i unscrew the plug currently in it, will it be an issue to screw in a new fitting complete with a tap? I am concerned the pressure of escaping diesel will stop me being able to screw the new fitment in? The tank is pretty full at the moment.

 

Do you have decent access in through the top of the tank (bolt on inspection panel or similar)? If so you could put a cork in the outlet pipe from the inside before removing the plug. I have done this successfully with a domestic water tank when the valve on the outlet needed replacing, but the access was there, and if anything got spilt it was only water.

 

I think I would rather wait until the tank is nearly empty, then pump out the rest, as others have suggested.

Edited November 21, 2012 by David Mack

[pmms]

A ball valve with the handle taken off can only be opened with " tools" ie a handle, (same as an acetelene cylinder )

the valve MUST be fitted with a "tools to remove plug,cap or blank". Check 2.8.1 in the current checking procedures.

 

Paul M

[dmr]

Hot Swapping is certainly feasible.

A good fitting air tight cap/breather will certainly help (sealed with Cling Film?)

You need:

Courage

Confidence

A little bit of luck.

Some sort of Plan B (containers) just in case it all goes wrong.

An assistant, again just in case.

 

Did something similar with the sump plug on the engine with almost zero spillage, but cold oil is more forgiving than diesel.

 

.......Dave

[jake_crew]

Ah yes, wait until a REALLY cold day (say -20'C), then the diesel should be very thick !

 

[bizzard]

A vacuum cleaner running with the nozzle fixed in the fuel filler might help a bit too by creating a bit of vacuum in the tank.

My post 14 is the way i did mine, lost about an egg cup full.

Edited November 22, 2012 by bizzard