A measure of the amount of magnesium dissolved in the water. It is part of total
or water hardness. It also causes scale if levels are too high.
MAIN DRAIN This term
usually refers to a plumbing fit- ting installed on the suction side of the pump
in pools, spas and hot tubs. Sometimes called the drain and is located in the
deepest part of the pool, spa or hot tub. It is not a drain, such as a drain on
a kitchen sink. Main drains do not allow the water to drain to waste but rather
connect to the pump for circulation and filtration.
MAKE-UP WATER This is
sometimes called "tap" or "refill" water. It is the water used to replace water
lost to evaporation, splash-out, leaks or swimmer drag-out in the pool.
MANIFOLD The branch pipe
arrangement that connects several input pipes into one chamber or one chamber
into several output pipes. A filter manifold connects several input pipes from
the filter septa back into one common pipe.
MARCITE Originally a brand
name for a white plaster finish coat from 1/8th to 1/2 inch thick applied over
the gunite or shotcrete.
MICRON A unit of length
equal to 1 millionth of a meter - it is .000394 of an inch. Microns are used to
describe the pore size of filter media. Sand filters have openings of 25 to 30
microns; cartridge filters have openings of 8 to 10 microns; and D.E.
(diatomaceous earth) filters have openings of 1 to 5 microns. Humans, without
magnification, can see objects 35 microns or larger. A granule of table salt is
between 90 to 110 microns.
Any substance that is neither animal or vegetable. It is any class of substances
occurring in nature, usually comprising of inorganic substances, such as quartz
or feldspar, of definite chemical composition and definite crystal structure. It
sometimes includes rocks formed by these substances. Ground water dissolves
these rock substances, and the dissolved minerals are present in tap water.
Depending on the kinds of rocks the water comes in contact with, the minerals
dissolved in the water may be just a few or they may be many. Water hardness is
mostly comprised of these minerals.
MULTI-PORT VALVE Also
called a rotary-type backwash valve - This valve replaces as many as 6 regular
gate valves. Water from the pump can be diverted for various functions by merely
turning the valve handle. The water may be sent to waste, used for backwashing,
bypassing the filter for maximum circulation, for normal filtration, filtering
to waste (rinse), or the valve may be closed to not pass water. The pump must be
off before changing a valve setting.
(31.45% hydrochloric acid) - Also called liquid acid - An acid used to reduce
the pH and alkalinity levels in pool water. It tends to be very strong, and is
not recommended for use in spas. It is also used in acid washing, a process that
removes stains and scale from pool plaster.