- M Tubing:
- An industry standard for copper tubing defined by the tube wall thickness. Identified by a "red" stripe.
- Macerator:
- A device, normally a pump with cutting blades, installed in a drain line between a toilet and the soil stack to reduce solids to liquid form.
- Magnesium:
- One of the elements (Mg) in the earth's crust. When dissolved in water makes water hard. The presence of magnesium in water is a factor
contributing to the formation of scale and insoluble soap curds.
- Main (water):
- The primary water supply in which all the branches of a water system connect.
- Main Line Trap:
- Also known as a whole house trap. Normally an in-line "running" trap utilizing a "U" shaped fitting with a vent.
- Male Fitting:
- A fitting that inserts or adapts into a female fitting.
- Male Threads:
- The threads of the pipe are on the outside.
- Male IPS (MIP):
- Male Iron Pipe Size - Standard external threads on pipe and fittings.
- Malleable Fittings:
- Fittings made of cast iron. Metal which is soft and pliable.
- Manganese:
- An element (Mn) sometimes found dissolved in ground water, usually with dissolved iron but in lower concentration; causes black stains and other problems similar to iron.
It can be removed by a water softener or it can be precipitated by chlorine at a pH of 9.5 or above.
- Manganese Greensand:
- Greensand which has been processed to incorporate in its pores and on its surface the higher oxides of manganese. The product has a mild oxidizing power, and is often used in the oxidation and precipitation of iron, manganese and/or hydrogen sulfide, and in their removal from water.
- Manhole:
- Access opening to a hole, usually with a cover, through which a person may enter a sewer, boiler, drain, etc..
- Manifold:
- A fitting that connects a number of branches to the main; serves as a distribution point.
- Manifold Pressure:
- The gas pressure in an appliance manifold upstream of the burner orifices.
- Manifolded Installation:
- Paralleling of water heaters for large hot water demand applications.
- Mapp Gas:
- A colorless, flammable gas made by combining liquefied petroleum gas with Methylacetylene-Propadiene. It is a stable, non-toxic fuel used in brazing and soldering.
- MC Tank:
- Acetylene tank holding 10cu.ft. of gas, used for plumbing, and once used to fuel motorcycles.
- MCL:
- Maximum Contanimant Level - The maximum level of a contaminant allowed in water by federal law. Based on health effects and currently available treatment methods.
- Mechanical Controls:
- Dials, slides, switches, knobs, buttons, and so forth used to operate ranges, ovens and cooktops.
- Mechanicals:
- The wiring, plumbing, and heating and cooling systems in a building; also the components with moving parts such as furnaces, plumbing fixtures, etc.
- Metal Fatigue:
- A breakage of the metal caused by the bending and flexing or the expansion and contraction of a metal part beyond its endurance limit.
- Meter Tailpiece:
- An adapter connecting a water meter to the water supply line.
- Meter Tile:
- The cylindrically shapedcasing that forms the pit to hold a water meter. It's usually made of plastic.
- Metering Faucet:
- Faucet which delivers a predetermined volume of water and then automatically shuts off.
- MHT:
- Male Hose Threads (threads on outside of connection).
- Micron:
- A unit of measure, one thousandth of a meter. Used to describe the pore size of filters.
- Millivolt:
- One thousandth of a volt.
- Minimum Run Time:
- The minimum length of time that the pump should run while refilling the pressure tank.
- Minispread:
- A special style of bathroom lavatory faucet having separate spout and handles, but designed small enough that it will fit 4" center-to-center faucet holes.
- Mission Coupling:
- A neoprene flex coupling, connecting PVC to PVC or clay to PVC.
- Mixer:
- The portion of a burner where air and gas are mixed before delivery to the burner ports.
- Mixing Valve:
- Mixes hot and cold water to achieve a specified delivery temperature.
- MNPT:
- This refers to the male pipe thread, in which the threads are on the outer side on the connection fitting.
- Moenstone:
- A blend of ceramic-like quartz (70%) and acrylic polymer (30%) that is impervious to chips or water spots.
- Monitor Cover:
- The cast iron lid that fits over a flange casting which is mounted on meter tile in a water meter pit. It consists of an outer lid, an inner lid, and the flange
casting in one or two pieces.
- Monobloc Faucet:
- A single-handle faucet, usually a lever.
- Most Probable Number (MPN):
- The term used to indicate the number of organisms which, according to statistical theory, would be most likely to produce the results observed in certain
bacteriological tests; usually expressed as a number in 100 ml of water.
- MPX:
- Male Pipe Swivel Connection.
- MTBE:
- Methyl Tertiary Butyl Ether. Used in gasoline to reduce air pollution, MTBE has been known to taint drinking water from leaking underground fuel storage tanks.
- Multiport Valve:
- Rotary type backwash valve. Can replace up to 6 gate valves.
- Multi-stage Pump:
- A pump that has more than one impeller.
- Municipal Water:
- Water supplied by a city for public use; tap water. Usually held in a reservoir.
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