What's pukka for jointing fittings (compression and straight threads)
for heating oil? I heard that PTFE tape was not OK. My Purimachos
green stuff says it's OK for oil but I wonder if it'd be that
effective - I don't think it gets thick and sticky over time like the
Also: it's a gravity feed system and it'd be easier to arrange the
pipework with a rise & fall to accomodate the filter and a butterfly
valve, as below:
| tank |
| ___?_ | |
| | | | |
-------------------------- ---| appliance |
Should I have an air bleed at a high point in the pipework? (the point
Or should I try not to have a fall at all (do-able, but awkward).
Stan the Span
email@example.com (Stanley Spanner) wrote in message
I believe that would be fine as youve drawn it. All that matters to
the oil is the relative heights of start and finish, and length of
pipe. Sharp bends would add more resistance to flow. As long as your
high point is below the top of the oil in the tank there is no
I used to think so, but it sadly proved not to be the case. I still do
not understand why, but with an arrangement very similar to the above, I
had to suck the bloody stuff through. Total drop of 1.45m over 50 meters
of pipe, and as far as I knew only down underground then up to the
fliter/boiler. All I can sday is that with air in it, it would not flow.
I repeat, common sense is on your side, bitter experience - or rather
diesel tasting experience, is on mine. On a long run, any uphill run is
a problem, no matter what the final height is. Once full of oil, both my
pipes ran freely under gravity, and no point in the pipe was above the
final outflow point. BOTH refused to flow with air in the pipes. I do
not understand this either.
In theory :-)
I usually put some green stuff on even new joints, and always on old
ones - belt & braces.
- or there's [been] a bit of grit in the joint, which has scored the
metal surfaces so they don't seal perfectly. (That's with those of us
who don't plumb in clean-room conditions :-)
.. and soft-as-butter fully annealed table Y tube <grrr>
What about parallel threads? (The filters and butterfly valves all
Normally I'd use PTFE: the panel at Plumb Center reckoned that was out
for oil; but I've just checked Treloar who says "Petroleum resisting
compounds and PTFE tapes which remain slightly plastic make the most
satisfactory joints; hemp and hard-setting jointing compounds should
be avoided". I assume he means PTFE tapes in general, not 'Petroleum
resisting PTFE tapes' as I understand PTFE is pretty inert stuff and I
doubt it would be bothered by heating oil.
OTOH he also says soft soldered joints are out, which means I've got
more &%^* compression joints to make on soft tube :-(
Stan the Span
Compression, but beware that they are weak at the normal pipe diameter.
PTFE tape doesn't work well - use Red Loctite to seal. Try to avoid up
and under routing - you will just have to bleed it - don't put bleed
valves on, just steel yourself and suck the bloody pipe full and then
never ever let it run dry again :(
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