The boat is sitting on stands (thought I was at the end of a restoration
project)... all fittings are dry... caused a change of pressure to the
fuel tank moving a pipe for the fuel fill trying to remove the old fill
hose... top and side of tank are dry... we started the day, a rainy day, we
thought we'd finish assembling the engines but not a chance... no gas
fumes... started cleaning and organizing as only a few weekends left till
having her picked up for return to the sea... old, deteriorating fuel fill
hose needs replacing so I went to remove the hose... it would not budge...
but I caused a pressure change in the tank...

Me thinks (scary thought after a few tequila shots to get over this
discovery) the pressure change shifted some sediment over a hole and thus
the leak...

So a clean bidge with some clean water then became topped with petrolium...
thus the though there is a leak in the big tank under a finished floor...
thus the need to figure out how to test it to confirm and also the need to
drink more...



"Gould 0738" wrote in message
...
Is there a strong smell of gasoline in the bilge? Could be a case of
sloppy
fittings, but if you're leaking gasoline out of the tank in any quantity
at all
it's going to smell pretty stong.

Do you have water in your bilge? Is there a petrochemical film on top?

What makes you suspect that you have a leaky tank?

Tony Abbott wrote:
The boat is sitting on stands (thought I was at the end of a restoration
project)... all fittings are dry... caused a change of pressure to the
fuel tank moving a pipe for the fuel fill trying to remove the old fill
hose... top and side of tank are dry... we started the day, a rainy day, we
thought we'd finish assembling the engines but not a chance... no gas
fumes... started cleaning and organizing as only a few weekends left till
having her picked up for return to the sea... old, deteriorating fuel fill
hose needs replacing so I went to remove the hose... it would not budge...
but I caused a pressure change in the tank...

Me thinks (scary thought after a few tequila shots to get over this
discovery) the pressure change shifted some sediment over a hole and thus
the leak...

So a clean bidge with some clean water then became topped with petrolium...
thus the though there is a leak in the big tank under a finished floor...
thus the need to figure out how to test it to confirm and also the need to
drink more...


Being petrol it's a bit scary bananas & you don't say how much is in
the tank.

The usual method to "test" is to;
(i) clamp all usual outlets at the end of their runs (that way you test
the unions taps etc),
(ii) fill with diesel or water,
(iii) have a small diam hose clamped to the fill or even the vent,
(iv) lift it 2ft above the top of the tank (=1 psi),
(v) top it up, mark the level at 2 ft up then
(vi) see if it's level drops over a short time.

Also once a light positive pressure is there, you can look around
accessible areas for leaks (notoriously difficult small leaks can
capillary a long way before becoming apparent/a drip).

Being petrol & the boat being on stands you can probably syphon what's
in there out pretty easily into 205 ltr drums.

Testing non pressure designed containers with air is always dangerous,
more so even than using petrol as the test liquid; also it's very
difficult to "limit" very low air pressure, particularly suggested don't
give the tank 3psi, it'll be creaking & groaning with a liquid head
pressure of 2 ft (1 psi).

The USL code for commercial boats, forbids testing with more than a 4
ft head (2psi), because rather than looking for leaks you'll be creating
them:-) or damaging the baffles/hull/decks as the tank bulges.

K


"Gould 0738" wrote in message
...

Is there a strong smell of gasoline in the bilge? Could be a case of

sloppy

fittings, but if you're leaking gasoline out of the tank in any quantity

at all

it's going to smell pretty stong.

Do you have water in your bilge? Is there a petrochemical film on top?

What makes you suspect that you have a leaky tank?

K. Smith wrote:

The usual method to "test" is to;
(i) clamp all usual outlets at the end of their runs (that way you
test the unions taps etc),
(ii) fill with diesel or water,

WRONG

Do *not* fill a fuel tank with the wrong kind of fuel, or water. I think
most people would be smarter than to do this anyway, but I felt I should
speak up just in case.

Note to rec.boats regulars- I generally skip K.Smith's posts but checked
this one.

DSK

Actually filling a tank with water is a comon way to test for leaks.
Particularly with large tanks where filling the tank with fuel can be costly
and dangerous. It's not like a large fuel tank doesn't get a little water
in it from time to time.

"DSK" wrote in message
...
K. Smith wrote:

The usual method to "test" is to;
(i) clamp all usual outlets at the end of their runs (that way you
test the unions taps etc),
(ii) fill with diesel or water,

WRONG

Do *not* fill a fuel tank with the wrong kind of fuel, or water. I think
most people would be smarter than to do this anyway, but I felt I should
speak up just in case.

Note to rec.boats regulars- I generally skip K.Smith's posts but checked
this one.

DSK

JamesgangNC wrote:
Actually filling a tank with water is a comon way to test for leaks.
Particularly with large tanks where filling the tank with fuel can be costly
and dangerous. It's not like a large fuel tank doesn't get a little water
in it from time to time.

That last point is true, but that doesn't make it a good idea to
deliberately fill the tank with large amounts of water.

Frankly, if filling a tank with water is so common, how come there is no
mention of it whatever in either standards or in contractors handbook?
It seems to me that cleaning the tank afterwards would be more trouble.

Gene's phenolpthalein test is a lot more common in my experience,
although I haven't seen it done with large tanks which are usually air
tested after scrupulously gas freeing them.

Fair Skies
Doug King

Cleaning the tank afterwards is about the same for all these options. If
you fill it with water getting the vast majority of the water out is easy,
just syphon it out. It the last remaining water or whatever that is
trouble. I take the fuel gauge sender off so I can put a syphon all the way
to the bottom. Most pickups do not go to the bottom so that whatever water
or crud accumulates will not get picked up.

"DSK" wrote in message
...
JamesgangNC wrote:
Actually filling a tank with water is a comon way to test for leaks.
Particularly with large tanks where filling the tank with fuel can be
costly
and dangerous. It's not like a large fuel tank doesn't get a little
water
in it from time to time.

That last point is true, but that doesn't make it a good idea to
deliberately fill the tank with large amounts of water.

Frankly, if filling a tank with water is so common, how come there is no
mention of it whatever in either standards or in contractors handbook?
It seems to me that cleaning the tank afterwards would be more trouble.

Gene's phenolpthalein test is a lot more common in my experience,
although I haven't seen it done with large tanks which are usually air
tested after scrupulously gas freeing them.

Fair Skies
Doug King