- Natural Gas:
 - A colorless, odorless fuel derived from the earth, consisting primarily of Methane. Odors are added to aid in leak detection.
 
  
- Negative Pressure:
 - Less than atmospheric pressure.
 
  
- NEMA:
 - National Electrical Manufacturers Association.
 
  
- Neo-Angle:
 - Term used to describe shower receptor or bathtub that fits into a corner. Two corner walls butt up against the fixture.
 
  
- Net Usable BTU:
 - The portion of a fuel's heat energy actually transferred into the water by a heater.
 
  
- NH:
 - No Hub.
 
  
- Nipple:
 - A short length of pipe installed between coupling or other fittings.
 
  
- Nipple Extractor:
 - A tool used to unscrew sections of pipe.
 
  
- NKBA:
 - National Kitchen and Bath Association.
 
  
- No-Hub Connector:
 - A connector for no-hub iron pipe consisting of a rubber sleeve and a stainless steel band secured by hose clamps. A variation, a neoprene sleeve with two
adjustable steel bands, is used for connecting dissimilar materials, as when connecting new plastic pipe to an existing cast-iron drainpipe.
 
  
- Nom:
 - Nominal. Usually refers to the inside diameter of trade sizes of copper pipe and some CPVC pipes. Not for iron pipe connections. For example, a 1/2" Nom comp.
fitting is actually 5/8" because 1/2" pipe has an OD of 5/8".
 
  
- Nominal Size:
 - Size used for identification only; not literal dimensions.
 
  
- Non-CFC:
 - Foam insulation that minimizes the use of Chlorofluorocarbons.
 
  
- Non-ferrous:
 - Not containing iron.
 
  
- Nonpotable:
 - Not suitable for drinking.
 
  
- NPS:
 - National Pipe Straight threads standard, same as IPS.
 
  
- NPS (Discharge):
 - Nonpoint Source pollution: nutrients, sediments, toxic substances, and pathogens that degrade waterways. NPS occurs mainly through storm water runoff.
 
  
- NPSHA:
 - Net Positive Suction Head Available to prevent cavitation of the pump. It is defined as atmospheric pressure + gas pressure + static pressure - vapor pressure -
friction loss in the suction piping.
 
  
- NPSHR:
 - Net Positive Suction Head Required to stop a pump from cavitating. This number is usually provided by the pump manufacturer.
 
  
- NPT:
 - National Pipe Tapered thread standard. Same as IPS.
 
  
- NRDC:
 - Natural Resources Defense Council - A non-profit environmental advocacy organization that seeks to protect the encironment and the nations natural resources.
 
  
- NSF:
 - National Sanitation Foundation.
 
  
 
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