I'm not somewhere to measure this right now, but it's been my experience that US copper pipes are actually hard metric but named to a nominal inch size which is some instances can be way off the actual size. I can measure this stuff when I get home, I seem to recall the 1/2 inch is actually 15 mm OD on the pipe ID on the fitting that connect the pipes. I think the 3/4 inch is 23 mm but I'd have to check.
Mike Payne ----- Original Message ----- From: Pat Naughtin To: U.S. Metric Association Sent: Wednesday, 14 January 2009 03:12 Subject: [USMA:42337] Pipe fittings in the USA Dear All, I found this Q and A at http://en.allexperts.com/q/Plumbing-Home-1735/2008/3/Copper-pipe-sizes-1.htm where an Australian asked for information about copper pipe sizes in the USA. The answer included this line: But to answer your question, copper pipe and fitting for plumbing are called out by their nominal size. 1/2" copper pipe is actually 5/8". 3/4 is 7/8, etc. However, refrigeration tubing and ACR pipe (cleaned and capped for med gas) is called out by it's OD. 1/2" ACR is the same size as 3/8 type L, M or K. 5/8" ACR is the same as 1/2" L, M or K. I was amused to find that 1/2 is actually 5/8 etc. and I have no idea what l, M, or K might mean. By the way, the Australian referred to a 'nominal' 1/2 in. pipe that has really measured 10 millimetres (inside diameter) and 12 millimetres (outside diameter), giving it a wall thickness of 1 millimetre, for many years. Cheers, Pat Naughtin PO Box 305 Belmont 3216, Geelong, Australia Phone: 61 3 5241 2008 Metric system consultant, writer, and speaker, Pat Naughtin, has helped thousands of people and hundreds of companies upgrade to the modern metric system smoothly, quickly, and so economically that they now save thousands each year when buying, processing, or selling for their businesses. Pat provides services and resources for many different trades, crafts, and professions for commercial, industrial and government metrication leaders in Asia, Europe, and in the USA. Pat's clients include the Australian Government, Google, NASA, NIST, and the metric associations of Canada, the UK, and the USA. See http://www.metricationmatters.com for more metrication information, contact Pat at [email protected] or to get the free 'Metrication matters' newsletter go to: http://www.metricationmatters.com/newsletter to subscribe.
