Never done any plumbing before, but am quite handy with most other DIY.
Planning to replace a dead electric shower - pretty much a like for like replacement. The old one is no longer available, but the fittings and their position in the new one look exactly the same.
Shouldn't be a big job I think - hopefully just a disconnect, remove from wall, connect new one and fit to wall.
In the manual of the new shower (see here
formatting link
it mentions (page 16, point 17) that I should use 1/2" fitting to connect the shower to the supply pipe. This is all already there.
Assuming that it is either damaged or very hard to remove, I want to use a new olive for the shower inlet. Is it a 12mm one that I need?
No. Pipe comes in 10mm (for central heating), 15mm, or 22mm. All of these are outside diameter. Imperial measurements on the other hand were *inside* diameter (which is what you care about with water pipes).
So you need a 15mm olive .... but:
If you look at the diagram, from the bottom I imagine
the inlet supply is already there.
the compression nut on the inlet supply side is already there
the olive on the inlet supply side is already there
the 1/2" BSP nipple is already there
... just leave those all in place.
Undo the compression nut on the top of the nipple, and remove the old boiler. This will remove the compression nut, so saw through the old inlet connector to release the nut.
Do *not* attempt to reuse the old olive on the inlet connector - the compression fitting will have deformed it into the inline connector to make a water-tight (and probably gas-tight) metal-to-metal seal.
Fit the boiler to the wall, push the old nut onto the new inlet connector; push the new 15mm olive that you purchased at great expense (*) onto the inlet connector; wiggle the inlet connector into the BSP nipple; tighten up until its tight (but don't over-tighten). Done.
If the joint leaks, tighten it up another 1/4 or 1/8 turn. I tend to use a bit of toilet paper to test for leaks; if it comes out dry, and then is still dry an hour later you are done (but check the next day too).
*: "Great expense" - in the old days a builders merchant would probably just point you at the charity box if you only wanted one olive.
You can also apply a smear of Boss-white or PTFE tape to the threads - this does nothing to improve the seal (the seal doesn't occur on the threads), but it does lubricate the threads, so it's easier to turn the nut.
IME the nuts on old compression fittings are easy to remove. If not, an adjustable spanner given a sharp tap with a hammer usually does the trick. Shouldn't need anything new, just connect the nut to the new shower
Unless the old fitting has been done up by a gorilla, there's usually enough deformability left in the old olive to re-use it in my experience. Of course using a new olive is the proper way but it's always worth trying, particularly in a shower where a leak is easy to spot and "harmless".
Are you sure,in the days of gal pipe this was correct but not with copper. If it was interior measurement thicker gauge pipe would not fit the fittings. Common sizes used in UK houses, Copper pipe is available in a number of sizes commonly:
8 and 10 mm - for use microbore central heating systems 12 and 15 mm - generally for connections to individual taps, appliances etc. 22, 28 and 35 mm - generally for long runs where use of 15 mm piping would cause excessive pressure drop.
Yes, I'm sure - I've gold old imperial plumbing in some bits of this house.
Modern UK plumbing pipes are indeed measured by OD, but the for the old imperial pipes it was the ID - a nominal 1/2 inch, presumably the relevant BS specified wall thickness as well.
This means that an old half inch pipe is near as dammit the same OD as modern 15mm pipe (it's a slightly larger diameter) and so normally you can use modern fittings on old pipe - compression is normally ok, solder fittings, depends on the fittings , plastic I wouldn't use as I wouldn't trust it with the wrong sized pipe.
With 22mm pipe and old 3/4 inch pipe, the difference is greater and so you need a different olive in compression fittings, or to use special solder fittings to convert to modern pipe size
So would I but, 12mm is not a pipe size normally used in UK plumbing.
It's an ID/OD thing. Pipe sizes quoted in imperial units are the ID (internal diameter). Thus a 1/2" pipe has an ID of 1/2", or 12.7mm. Allowing approximately 1mm for wall thickness, this gives a pipe of ~14.7mm OD (over-all or outside diameter). Pipe sizes quoted in metric units are OD. Thus a 15mm pipe has an OD of 15mm, which is close enough to the 14.7mm OD of 1/2" imperial pipe, and fittings for 15mm pipe work fine on 1/2" pipe. But the same isn't necessarily true for larger imperial sizes.
Are 1/2" and 3/4" pipes sufficiently similar to 15 and 22 mm ones that they can use the same compression fittings as long as you use the correct olive (eg 1/2" versus 15 mm)?
Presumably this is not the case for soldered fittings where it's a much tighter fit. Are there imperial-to-metric adaptors which will allow a modern
15 mm appliance to connect to old 1/2" pipe - or would you always use a compression fitting for that purpose?
Think that may be the case. Although not sure if it works both ways.
I have end feed adaptors to convert from imperial to metric. Which is why I'm not that certain about compression fittings. Except that I've got a bag of imperial olives which I've marked as 1/2".
Are these old 1/2"and 5/8"and 3/4" imperial pipes you are talking about copper or steel? In AU our old system was steel gal nom ID pipe but when we went to copper it started out 1/2" 5/8" 3/4" 1" OD (slightly differing bores according to wall thickness. When we started talking metric the pipe stayed the same, it is now
12.7mm 15.5mm 19.1 25.4 OD so fittings stayed the same. 15.9 (5/8") is not used much any more.
12.7 is used mostly for short final runs on hot and cold water mains pressure, bigger for the beginning of the run and feeding multiple outlets and for gravity feed Gravity feed is not seen much on any new domestic housing. For gas all sizes except maybe 5/8" is used depending on load and volume needed.
Right. So you used 1/2" OD. In the UK we used 1/2" ID.
Whereas we changed the pipe (slightly), *and* started measuring the OD. So the equivalent to 1/2" imperial is 15mm metric (but, as stated upthread, you need to use a special olive to use a 1/2" pipe in a 15mm compression fitting).
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