Old plumbing sizes..

[Zebra]

Hey all. I have the copper insides of an old rectangular immersion tank which my friend Giraffe and I removed from a flat. I want to make it into a rainwater butt. The outlet is a male spigot which looks like a 1" fitting but has a finer thread and 1" female couplers won't fit on it. Any ideas what it could be or what I could get to fit on it? I'd like to put some sort of a tap on it. I'm guessing it dates from the 70s.

 

[a twig]

NPT rather than BSP?

 

[Gothichome]

I do not know if you use NPT (national pipe thread) there in Briton. If so, it could be your trying to instal an NPT to an NPTF nipple. NPTF (national pipe thread fuel) is a less common thread and is designed to give a none leak joint with out the use of pipe dope. The thread pitch are not compatible on sizes over 1/2 inch. Only other option is the dreaded British Whitworth thread, hated in all parts of the world except Briton. But I think even there it’s an obsolete thread by the 70’s.

 

[Craig89]

If its a male thread then it should be easy to count the TPI (threads per inch). Hold a rule against the thread, starting at the crest of one thread and then count how many threads are in 1 full inch, not including the one you line up with at the start. If you then roughly measure the outside diameter of the thread it should be pretty straight forward to determine what it is. (1/4 has to be deducted for a BSP size as say a 1/2" BSP thread would have a 3/4" outside diameter, the size refers to the bore diameter). I would be surprised if it wasn't a BSP thread as although BSW and BSF were phased out in favour of metric, BSP remains the standard in the UK for pipe fittings.

Hope that makes sense, Craig

 

[Flyfisher]

Any ideas what it could be or what I could get to fit on it? I'd like to put some sort of a tap on it. I'm guessing it dates from the 70s.

I had similar issues when trying to connect to some old iron pipes in our house. I'd recommend Stevenage Plumbing near you, but don't go into the showroom go to the trade counter around the back of their unit instead. In my case I could take apart some of the fitting and take them in and say I want to be able to connect this to whatever, whereupon they would disappear into the stores and come back with the appropriate fittings. Might be more difficult if you can't physically take the item with you, but they might well be able to identify what you need if you take in some photos and measurements.

 

[a twig]

I do not know if you use NPT (national pipe thread) there in Briton. If so, it could be your trying to instal an NPT to an NPTF nipple. NPTF (national pipe thread fuel) is a less common thread and is designed to give a none leak joint with out the use of pipe dope. The thread pitch are not compatible on sizes over 1/2 inch. Only other option is the dreaded British Whitworth thread, hated in all parts of the world except Briton. But I think even there it’s an obsolete thread by the 70’s.

Ha - so hated that the USA basically copied it - UNC thread is basically identical to Whitworth in terms of pitch etc - Whitworth just uses “rounded edges”rather than “sharp”. The confusion with Whitworth size is just because it refers to the diameter of the screw rather than the distance between the flats of the head. Remember that and you’re sorted

 

[Gothichome]

I do not know if you use NPT (national pipe thread) there in Briton. If so, it could be your trying to instal an NPT to an NPTF nipple. NPTF (national pipe thread fuel) is a less common thread and is designed to give a none leak joint with out the use of pipe dope. The thread pitch are not compatible on sizes over 1/2 inch. Only other option is the dreaded British Whitworth thread, hated in all parts of the world except Briton. But I think even there it’s an obsolete thread by the 70’s.

Ha - so hated that the USA basically copied it - UNC thread is basically identical to Whitworth in terms of pitch etc - Whitworth just uses “rounded edges”rather than “sharp”. The confusion with Whitworth size is just because it refers to the diameter of the screw rather than the distance between the flats of the head. Remember that and you’re sorted

Twig, was just dealing with a whitworth thread issue last week on an old Perkins Diesel engine. After running a tap a couple times and a couple of chases, I finally got the 1/2 bolt to thread into the whitworth bore. Trying to find a whitworth bolt any were other than Briton, you might as well be looking for free gold. :lol:

 

[paulc]

NPT rather than BSP?

Highly unlikely to be NPT unless the tank was sourced from the USA.
A BSP thread will be 11 threads per inch. If it is looking like it might be 26, then I'd take a stab at it being a 1 1/4" British Standard Brass. If all else fails, I'd suggest soldering a spigot into the stub sticking out of the tank. Might need access to a lathe to turn a bit of pipe to suit though.

 

[Zebra]

Thank you everyone, you've given me some things to ponder and look up.

 

[CliffordPope]

If it's going to be used for nothing more arduous than a rainwater butt then If I couldn't easily find a thread that fits I'd just use Chemical Metal to seal a bit of ordinary pipe inside it.

 

[Zebra]

If its a male thread then it should be easy to count the TPI (threads per inch). Hold a rule against the thread, starting at the crest of one thread and then count how many threads are in 1 full inch, not including the one you line up with at the start. If you then roughly measure the outside diameter of the thread it should be pretty straight forward to determine what it is. (1/4 has to be deducted for a BSP size as say a 1/2" BSP thread would have a 3/4" outside diameter, the size refers to the bore diameter)

So, I've measured the TPI, and I haven't got a full inch to measure, so over a distance of 12/32 of an inch, there's 7. So to get to a full inch you'd multiply that by, erm, 12/32 = 3/8 so multiply 7 by, erm, god I hate imperial....erm, I think I get to 952 TPI, no, erm, 18.6?? The outer diameter of the spigot is 7/8 inch, so perhaps it's 1/2 inch BSP? 5/8 inch BSP? Oh do you know what, I think I'm going to follow ClifforPope's and PaulC's advice, and glue something on.

 

[Zebra]

Here's the thing......I've measured it, still no clue what it is....

 

[Gothichome]

To my eye that looks to be a straight thread, not pipe at all. I see a tapered internal shoulder, suspect it has a nut and compression ring (Ferrel) fitting.

 

[Craig89]

Your calculations are correct giving a tpi of 18.6 so likely to be 18 or 19 tpi. Some small BSP fittings have 19tpi but nothing that big. It could be anything really. If I had it in my hands to measure then I could screw cut you something up but as it doesn't appear to be anything standard then harder to do so. There are so many different possibilities it's very hard to say, you would have thought it would have been standard for getting standard fittings for it when it was installed but who knows.

I made an extended overflow adapter for my bath recently and the threads that were used originally just didn't follow any standard. As long as the male and female threads were the same then that's all that mattered in that instance.

Like as has been mentioned it may be easier to find something that fits inside/over the spigot with a standard BSP thread in for a tap and affixed with epoxy.

Sorry couldn't have been of more help

 

[a twig]

It’s definitely not 28mm compression? :mrgreen:

 

[DJH]

Prestec tank connector...nut and cone required Zebs....

 

[DJH]

Prestex....

 

[Me!]

A 1 1/16" external diameter and with 18 TPI could be a Unified Extra Fine (UNEF) thread. But if it is, then unfortunately I don't think you are likely to find anything to fit it.
However, the current spigot is presumably far larger diameter than any tap you plan to fit to it, so the diameter will need to be reduced anyway. I'd use a long threaded brass tube the correct size for the tap you want to fit, so probably something like this -
https://www.stevensonplumbing.co.uk/brass-running-nipple-1-2-inch-100mm.html
and fit it through your current spigot using a flange nut and sealing washer on the inside of the tank and another nut on the outside, and then screw your new tap to the end.