How to / DIY > Engines

brass water drain tap


Hi There,

I have a Lister JP2 and I'm looking for a brass water drain tap (see picture).

Have found some, but I'm not sure what type I need to fit in. Do I need a 1/4" of r 3/8" BSD?

Hopefully somebody out ther nows  ;D

Best Regards,


Hi Jos,
Sorry I cant help with the exact size but what I do is measure the hole size and compare that to a number of taps or using the hole size Google it. I am not familiar with BSD but I am with BSPT (British Standard Pipe Tapered). If you meant BSPT then the following sizes may help;
1/4" BSP =11.2mm drill size
3/8" BSP = 14.75mm drill size
I feel it should be the tapered thread and not a parallel thread which is BSPPL where the drill sizes are slightly bigger, 11.5mm & 15.0mm respectively.
Sorry for the detailed reply.

Thank you
I'm gonna take a look this friday

I agree with Cobbadog. On every Lister of that vintage the fittings, meaning plugs, taps, even some of the tube nuts are BSP. If set up for a sealing washer there will be an area machined flat around the threads and the tap will need BSPP threads and you need a seal washer. More likely it uses the tapered version or BSPT.


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