A fried of mine left the cap off a 2" inspection hole (screw-on type) on
her domestic oil tank for the past couple of weeks. I can't imagine
much rain has got in but what's the best way to go about checking and
She said she rang her suppliers but they weren't particularly helpful
It is rarely a problem. The takeoff pipe is normally a few cm above the
bottom of the tank and so modest quantities of water and crap that
collect there are not sucked up.
There could well be a filter/water trap associated with the boiler as a
It's a single skin plastic tank very similar to this fella (Deso H1235T):
The gauge is fubar. So when my friend went to dip the level, she left
the cap off. In the image, it's the silver inspection aperture just to
the right of 'Deso'. Admittedly I'm going by memory but I didn't think
it was as big as 4"
Probably won't do any real harm but it may shorten a metal tanks
lifetime a bit by facilitating more rapid rusting from the inside.
Although that happens anyway with age since the fuel tends to be cooler
than its surroundings and water from condensation accumulates inside on
the exposed cold metal surface.
Mine looked fine when I scrapped it but was in fact etched through from
the inside with rust held together with many layers of Hammerite. It
failed on the water to fuel boundary with a noticeable thinning. It was
only with the tank empty and when they came to lift it off the base and
that it fell apart that I realised quite how bad it really was.
The guys who came to swap it thought I was being unduly cautious.
Plastic ones are impervious to water ingress unless you add so much that
the level goes above the take-off point. More annoying on a bunded one
is that any water in the outer bund may set off the leak alarm.
I wouldn't worry too much. Mine was provoked into leaking by an
overfilling accident. It might have lasted another year or two but for
that and the leakage was gradual as trace of rainbow oil from one side
visible clearly after rain.
Worth keeping an eye out for any traces of oil escaping though.
All modern tanks where I live have to be bunded - water course nearby.
Didn't need to - you could see where the internal water line had been.
The metal at the water height was so thin and razor sharp under the rust
which in places had broken off when the top came off...
All fuel (and some water) was pumped into a spare tank on their truck
whilst work proceeded. I hadn't fully understood this finesse and so
there was only 100L or so of oil in my tank.
I guess the corrosion of rusting needs water and oxygen so that the
interface region is always going to be the worst affected.
As someone else has said you can get dip sticks with an indicator on to
detect water at the bottom of the tank something along the lines of
cobalt chloride indicator paper.
Shouldn't be a problem but there is often a drain off valve on oil tanks to
get rid of condensed water.
Should have a valve fitted with a plug in the end. Lower than/just below
the oil take off valve/line.
But may just be plugged off.
Oil tank shoud be laid to a slope, drain valve at lower end of the slope,
oil take off at other end,
Shouldn't be a problem but there is often a drain off valve on oil tanks to get rid of condensed water. Should have a valve fitted with a plug in the end. Lower than/just below the oil take off valve/line. But may just be plugged off./q
In theory yes.....
If the steel tank is old, that drain tap can be corroded so badly it won't open, or worse, attempts to open it shear it off or cause failure of the corroded tank around it.....
On Mon, 15 Dec 2014 16:10:52 +0000, Bob Minchin wrote:
Until the level of water gets to the outlet and thus into the pipe
work, finding a low point, building up there and when it freezes
blocks the oil feed...
Wrong end, of the line, best is a glass bowl filter at the tank. This
will catch any water leaving the tank and you can see/clear it before
it becomes a problem further down the line.
As for finding out how much water is in the bottom of the tank. You
can get a goop that you smear on the last few inches of a suitable
dipping stick and dip the tank. The goop changes colour where it gets
Such goop can be found e.g.
or look on ebay for Kolor Kut.
First thing is to find out whether there is a problem or not.
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