Getting your measurements correct before you cut or order can save so much time in having to return to a merchant for incorrect pipe or fittings, as well as incorrect cutting of pipe.
Outside Diameter, Not Bore
When buying copper pipe it is usually sold by the outside diameter (OD) in the UK. Therefore a 15mm pipe will have an internal bore of approximately 13mm. Make sure you measure the outside of the pipe using your vernier calipers and check the fitting label for the size quoted. This will be the OD of the pipe.
Reading Nominal Sizes on Unmarked Pipe
Old or unlabelled pipes can be difficult to identify. Measuring the outside diameter of a suspected copper pipe with a set of vernier calipers will give you a very accurate reading. Based on current UK standards, the outside diameters of copper tubes are defined by BS EN 1057 and would be approximately 15mm, 22mm or 28mm. A measurement that falls within a single millimetre of any of these sizes can safely be assumed to be that size.
Allow for Fitting Insertion Depth
All fittings have an insertion depth into the socket of the fitting. This is often given on the fitting label. For a standard 15mm compression fitting this would be around 13-15mm and for a 22mm it would be around 16-18mm.
Measuring Around Bends and Offsets
For a run with bends measure to the centre line of the bend. Add the two straight lengths together. Then deduct the fitting’s socket allowance at each end. Don’t forget to make a rough sketch to help work out the total length of pipe required for your pipes and fittings run.
If you are looking for Copper Pipe, see //watkinspowis.co.uk/products/copper-pipe-fittings-and-press-systems/.
Measure twice, cut once.
