Water contamination in heating oil tank?

[richi]

So here's my next dumb question about oil boilers: What's the best way to deal with water contamination?

 

Background: A few peoples in my rural-ish area got caught out this winter with in-tank condensation causing too much water at the bottom of their tanks (it gets above the bottom of the inlet and then kills the pump). Are the scavenger-on-a-string devices any good?

[Jeremy Harris]

The only time I installed an oil boiler I fitted a water trap/filter in the feed pipe.  Not a cure for a lot of water in the tank, but a very good visual indicator of water being present, as the trap/filter had a glass bowl and water was clearly visible.

 

If water does get into a tank, then doing as you do with aircraft fuel tanks on a regular basis, just carefully draining it off from the very bottom of the tank should work OK.  Not hard to do, as long as the tank is set up properly with a very slight tilt towards the drain fitting, and suitable precautions are taken to deal with any possible contamination (including disposal of the drained-off water).

[Gone West]

In the past I syphoned the bottom of my oil tank every couple of years to ensure water didn't build up sufficiently to come out of the outlet. In my tank the sump below the outlet pipe is large and it would take a lot of water before it caused a problem, although that was what happened the first time which led me to do the syphoning.