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?