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Fuel Drain Valve Thread older Aeropup With Aluminium Tanks?

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I have removed both drain taps from my aircraft as they were leaking slightly,  was intending to replace them with ones that had hose barbs to facilitate easy draining.  However I have no idea what the size or thread standard is,  valves have a number on them which mean nothing to me.  See pic.....

I was looking for something like this.....




Next thing is, are thread Guages available to use in measuring some of the aviation stuff please?  I know I need to get an AN bolt guage but that won’t help here


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Thanks for that idea, might go see a gas fitter and see what I turn up there....

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There's 1/8" BSP and there's 1/8" NPT. Don't get them mixed up, or the leaks will be incessant. BSP is 28tpi, NPT is 27tpi. In addition, the thread form is totally different between BSP and NPT.

Equipment built or produced in Australia or the U.K. normally uses BSP threads. Equipment built or produced in the U.S., normally uses NPT threads.


That is not a hard-and-fast rule, because American manufacturers produce equipment of American design in U.K. factories, and this equipment nearly always uses NPT threads.

Plumbing is where BSP rules in Australia - unless you just happened to import something (such as a U.S. built, 5th wheel caravan) with American plumbing - and then it will use NPT threads in the plumbing!




Tapered pipe threads utilise sealant (PTFE thread tape or liquid pipe sealant) to ensure a leak-proof seal. The vast majority of water pipes and plumbing in Australia, use BSP taper thread.


Parallel pipe threads utilise an O-ring or gasket, to seal, via flat or angled mating surfaces on the coupled fittings, or the fitting and the housing it screws into.


The "TSO C76" marking appears to indicate it's a Curtis 1/8" NPT drain valve, listed at the bottom of the linked page, below.






Edited by onetrack
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