• Welcome to PlumbersForums.net - The international free plumbing advice forum. Professional plumbers sharing advice with fellow plumbers and DIY alike. Register for free today! - Checkout the Plumbing Advice forum and then our Plumbing Videos area which still needs populating.

pipe size

Nominal Pipe Size (NPS) is a North American set of standard sizes for pipes used for high or low pressures and temperatures. "Nominal" refers to pipe in non-specific terms and identifies the diameter of the hole with a non-dimensional number (for example – 2-inch nominal steel pipe" consists of many varieties of steel pipe with the only criterion being a 2.375-inch (60.3 mm) outside diameter). Specific pipe is identified by pipe diameter and another non-dimensional number for wall thickness referred to as the Schedule (Sched. or Sch., for example – "2-inch diameter pipe, Schedule 40"). NPS is often incorrectly called National Pipe Size, due to confusion with the American standard for pipe threads, "national pipe straight", which also abbreviates as "NPS". The European and international designation equivalent to NPS is DN (diamètre nominal/nominal diameter/Nennweite), in which sizes are measured in millimetres, see ISO 6708. The term NB (nominal bore) is also frequently used interchangeably with DN.
In March 1927 the American Standards Association authorized a committee to standardize the dimensions of wrought steel and wrought iron pipe and tubing. At that time only a small selection of wall thicknesses were in use: standard weight (STD), extra-strong (XS), and double extra-strong (XXS), based on the iron pipe size (IPS) system of the day. However these three sizes did not fit all applications. Also, in 1939, it was hoped that the designations of STD, XS, and XXS would be phased out by schedule numbers, however those original terms are still in common use today (although sometimes referred to as standard, extra-heavy (XH), and double extra-heavy (XXH), respectively). Since the original schedules were created, there have been many revisions and additions to the tables of pipe sizes based on industry use and on standards from API, ASTM, and others.Stainless steel pipes, which were coming into more common use in the mid 20th century, permitted the use of thinner pipe walls with much less risk of failure due to corrosion. By 1949 thinner schedules 5S and 10S, which were based on the pressure requirements modified to the nearest BWG number, had been created, and other "S" sizes followed later. Due to their thin walls, the smaller "S" sizes can not be threaded together according to ASME code, but must be fusion welded.

View More On Wikipedia.org
  1. J

    Pipe size for heat pump system

    I am sizing the central heating pipes for a complete replacement. The property has an elongated floor plan so I have used a piping layout consisting of single flow and return headers running the length of the property and take-offs to and from radiators. Currently there is a combi boiler...
  2. H

    URGENT Pipe work rerouted to rads

    Hi I want to move the feed to my rads , as the route is too long,this would mean leaving approx 3 m of 22 mm flow and return plpework down beside the chimney breast still inline, and water being fed from 15 mm through 22 mm and back out to 15 mm.would this cause pressure problems or would the...
  3. I

    URGENT Flush pipe size 2” tapering to 1 1/2”

    Hi ive been asked to fix a leak on a flush pipe. I’ve never come across the pan type before. It looks like a closed couple but has a short flush pipe at the back. The pipe was clearly cut too short. it appears to be a 2” flush pipe going into the cistern but I looks like it’s 1 1/2” going into...
  4. J

    Vent pipe size for vented cylinder installed in 2005-6

    Hey, having searched this forum and last building regs (2000) from around that time... Any idea what the correct size is for a vent pipe for a vented hot water cylinder, gravity fed? I.e. the one that is continuously rising back up to the cold water feed tank for the cylinder? Have discovered...
  5. A

    Pipe size length bends junctions to Combi - affect on water flow rate?

    Hello! Advice required, please. Trying to understand implications of pipe size, length of run, and number of junctions etc. en route between the incoming water feed to the Combi-boiler. For various reasons it is difficult to get from stopcock to boiler without taking indirect route back across...
  6. A

    Pipe size on radiator any help would be nice

    Hi, does anyone know what size pipe this is? And what elbow I would need for a like for like swap?
  7. J

    Gas pipe oversizing. 22mm vs 32mm

    Just to be really clear I will not be doing any of the work mentioned below. This will all be carried out by Gas Safe Engineers. I'm looking to get a Gas Safe engineer to move a boiler from the main house to the garage. As part of this process I will also be getting the main gas supply and...
  8. J

    Gas pipe size

    I have a 22mm gas pipe going from my meter in the garage to my boiler in the kitchen. It has a 15mm t off the 22mm for a gas cooker. There is 8.5m of 22mm plus 6 90 degree bends, easily accessible in the garage, and 5m in the kitchen that will be difficult to access. If i change the 22mm in the...
  9. H

    Waste pipe size?

    Hello, I am looking to move some waste pipes in my house as I will be relocating a washing machine. My question is what size waste pipe do I have. I have measured with a gauge and get 56.08mm on the outer diameter. My understanding was the common sizes are 32, 40 and 50mm, I am aware there...
  10. L

    First fix pipe size?

    Hi, I'm about to pipe up my upstairs cold water to sinks and showers. It's a large 4 bed house, stopcock in the kitchen, middle of house outside wall, presently with 25mm pipe into a tap for building water. So upstairs sinks and showers are piped with tails hanging down in 15mm JG speedfit...
  11. M

    What size pipe for shower mixer

    Hi there! First post, so go easy on me. Please could I have some advice? I’m over-thinking something and it seems the type of HW system has a bearing on what size pipe is best for certain applications, so what better place to ask this question than a plumber’s forum? I have an unvented HW...
  12. G

    boiler install gas pipe size

    I need a new boiler and would prefer a 35KW combi boiler but wanted to know if my existing gas pipe will allow it. I wanted to check this first so i can look at my boiler options before getting somebody around. I don't have any other gas appliances and my existing pipe is 22mm. The gas meter is...
  13. B

    New Kitchen Waste Run Correct Pipe Size

    Hello PFM's, I have the pleasure of doing my first waste run for a new kitchen installed in a flat and was hoping for some advice. I need a 6-metre run to the stack where I am going to mark my 1:40/1:110 and split the difference at a 1:80 gradient. It will be discharging the kitchen sink...
  14. N

    Waste pipe size query

    Hi, I have a basin trap that has a 35mm chrome waste pipe supplied. I was wondering if this can converted to standard 32mm pipe as the chrome isn't long enough. I seems odd that the Chrome pipe isn't a standard size? Thanks
  15. J

    meter to boiler pipe size

    Hi, In the near future would like to change standard boiler for either same or combi , meter is at one corner of house and boiler diagonally opposite, pipe starts at 22mm from meter but ends up 15mm at boiler, concrete floors so assuming pipe goes up to and into 1st floor cavity and accross...
  16. B

    Pipe size and advice

    I am moving a radiator 4m across a single story extension. I haven't got access to the roof and I have a concrete floor. I am happy to route the pipe around the wall which would mean a pipe run of 6m. Should I use 22mm pipe or 15 mm. If I went across the floor it would be 4m but ruin the floor...
  17. L

    External condensate pipe size

    Hello, I have a rental property and had a new combi boiler fitted 2 years ago. No problems at all with the boiler, my only niggle is that the external condensate pipe is 32mm and fully covered with black insulation. This pipe runs almost 3 metres across the outside wall of the kitchen and then...
  18. J

    Pipe size and peak flow rate for converted flats

    Hello everyone, I have a building to be converted to 8 residential flats. It will be 7 one bedroom and 1 two bedroom flats which have one bathroom, one kitchen including washing machine but no dishwasher in each flat. I submitted the application to the water company to add 7 more water meters. I...
  19. L

    New boiler installation, pipe size question and controls please

    Hi, About to complete on a 3 bedroom semi detached house, upstairs downstairs. Current combi is upstairs in the bathroom and the intention is to buy a new Baxi HE33 and put it downstairs just off the kitchen so nearly directly below the old current boiler. Total number of radiators for the...
  20. jaydebruyne

    Steel pipe size identification

    i need to cap this pipe under the floor, will need to remove the elbow and fit a cap. Not sure what size the pipe is. 1/2 inch??
Creating content since 2001. Untold Media is a Registered Trademark.