Plumbing - Tapered Threads?

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What is with tapered threads ? :angry:

I just made a sight glass with poly carb tubing and compression fitting 'elbow' and the 1/2 in BSP thread is tapered so you have to use washers to cover up the thread where the locknut/flangenut would seize. I am bolting it on my HLT.

Has anyone else dealt with this. I can't believe I would ever have know all this crappy plumbing jargon and i am going to post pics etc when i can borrow a digital camera with names for the bits so no-one ever has to learn as much about plumbing as i have had to. :angry:

Lou :angry: :angry:

beer is good :D

Looking forward to your pics. I for one am totally confused when I visit Bunning. Is half inch the same as 15mm?? Is 3/4 inch the same as 20mm. The fitting says one and the label says the other ....but when you look on a ruler they don't line up....

I then buy some 15mm and 20mm fittings and go down to gardening to buy some quick connects and hose barbs and everything is 12mm or 19mm...Arrrr. It probably is perfectly logical to a plumber but it has got me stumped...

I actually gave Bunnings the bypass today and went to Whitworths - the boating shop. They had heaps of good fittings, (plastic,brass and SS) and easy to see and pick. Probably a few bucks more expensive but heaps easier.

I can tell you first hand that 20mm is not the same as 3/4" when it comes to pipes.

I purchased 3/4" poly pipe for a new mains pressure tap and right below this pipe at bunnings was the 20mm fittings. No 3/4" fittings to be seen.

Needless to say that the pipe leaked and I had to get the correct 3/4" fittings that sealed correctly.

Bunnings sell junk that isnt compatible :(

Know how you feel. At least it wasn't beer that leaked !!

Cheers -
It's not really that difficult guys , plumbing fitting are sold the same as pipe , the diameter is the inside measurement eg the diameter of the pipe it fits.
Tapered threads are very common, they are designed to wedge together so they seal well.

For a sight glass, you should try to get a bulkhead style fitting (forget bunnings). I just posted in another thread by coincidence about sight glasses


Tapered fitting = pain in the arse for fixing to pot.


Bulkead fitting - get these to make your life easyl (note the o-ring). I picked these up for $5.

Note the other end is the pushin fitting where the polycarb tubing goes.

brewiki: sight glass has suppliers and other details for making sight glass.
When you want to make a hole for a 1/2 inch fitting, the hole you need to drill is more like 21mm. As Batz pointed out, the 1/2" is the inside diameter of the fitting or the outside diameter of the copper pipe it is designed for.
Thanks guys!!!

I'm "technically challenged" when it comes to this stuff so plain english explainations much appreciated.

I am a former plumber so.....
Pipe is measured I.D or O.D ....... 3/4 Poly is actualy 25mm O.D (20mm I.D).
copper is measured I.D.
Tapered threads are exactly that .... meant for use with thread tape so that the fitting gets tighter as you turn it .
Non-tapered threads are generally only used on compression fittings.

Mains pressure poly is TOTALLY different from rural grade poly and irrigation poly.

Having a plumbing background is very handy for brewing.
could be a good business opportunity here Beersom...

"Plumbing for Dummys".

Thanks. Its starting to make sense.
PS - how bloody clever are these google ads. Just after posting the thread above I noticed the google ad up the top was:

"become a Plumber - start a lucrative career"........

Sosman pointed out a couple of posts back on this thread that tapered fitting were a pain in the arse for threading into a pot... and when you look at the photo he showed you can see why. If you are a half or a quater of a turn away from the direction you want the fitting to point, and it is tight, you are stuffed.
Witht he style of fitting shown, with the push in connector on the elbow, you can get these which twist the elbow separate to the thread part of the fitting.... these are far easier to work with, and you still get what i believe to be a better seal from the tapered thread.


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