Water in nature is never really pure, even when it falls from the clouds in its purest natural state, it contains some dissolved dust and gases as well as some suspended matters. After it has run over the surface of the ground or percolated through the rock layers, its impurities have greatly increased because water is practically a universal solvent and dissolves some of everything it touches. Therefore it needs refining or conditioning before using for domestic or industrial service. There are two general classes of water:
- Surface water such as:
- Streams and rivers
- Ponds, reservoirs and lakes
- Ground water such as:
- Spring waters
- Shallow well waters
- Deep well waters
- Mine waters
The present in water are:
- Dissolved solids
- Scale and deposit formers which cause total hardness, calcium, magnesium, alkalinity, sulfate, silica, iron, manganese.
- Corrosives includes chloride, sodium, total dissolved solids.
- Dissolved gases
- Corrosives such as oxygen (from air), carbon dioxide, hydrogen sulfide.
- Inert such as nitrogen.
- Suspended solids
- Turbidity, sediment, color, algae, bacteria, sand.
Effects of Water Conditions on Operation:
- Corrosion which causes:
- Poor flow caused by tuberculation
- Rusty water and stains (Iron, Steel)
- Blue-green stains (Copper)
- Scale formation – usually calcium carbonate:
Calcium carbonate is less soluble in hot water than in cold. The water tendency will increase in higher calcium, alkalinity, PH, total dissolved solids and temperature (Langelier Index). Scale reduces heat transfer (hot water generators, boilers, refrigerant condensers), reduces flow through pipes and interferes with operation of mixing valves, flushometers, and shower heads.
Scale can build up by:
- Iron and manganese oxides (usually in private well waters).
- Fine sand (well waters)
- Rust – from mains (disturbances – fires, construction).
- Algae – from reservoirs (common with unfiltered supplies)
- Sediments, fly ash, micro-organisms from air contact in cooling towers, etc.