"technics100" wrote in message
...

I had the boiler guy out today to have a look at it. He said that the
oil had water in it, but couldn't see where it was getting in. The oil
line runs underground for a few meters, so it may have a hole in it and
be taking in water. He replaced the jet and said it was soaked with
water. Boiler is running now, but I just have to find out where the
water is getting in.

Very unlikely to be entering against the pressure of oil within the pipe!
The usual place for water to get in to oil is via the top of the tank which
someone has stood upon causing the "dishing" to collect rainwater which
eventually rust through. Other places possible are sight gauges which have
lost their rain cap and are located under a leaking gutter, tank lids which
fit poorly and are under a leaking gutter also.
Is your tank located where someone you could have upset might find it
entertaining to put a hose into it?
Its a very remote possibility that you might have had a contaminated load
delivered but I'd put this a long way behind any other sources.
If your tank is set up correctly it should slope away from the outlet and
have a drain at the low end. If you have one, run some off from here into a
bucket and check visually and by dipping a bit of cloth for a burnability
test for water ( I went to a tank last year which had been vandalised and
found clear liquid for a depth of about 200mm but it wouldn't burn, after a
lot of draining off this underlying water eventually fuel arrived). Its
often possible to get rid of any water collected in the tank via this
method, in fact in days of old it was normal to do this as part of a six
monthly service, usually blaming water found on condensation rather than the
real source of refinery contamination. Modern production and storage methods
have all but stopped water being delivered in the fuel.