General Water Analysis Information

General Water Analysis Information

A brief explanation of the terms commonly found in your water analysis reports.  Each system has its own chemical parameters and required levels.  We hope this aids you to monitor our service to you in a more knowledgeable manner. Additional information is provided, such as that about  equipment malfunctions when observed.

Analysis Number:  The number under which the sample was registered in the lab.

Source:  Indicates where this water sample was collected.

pH:  The measure of acidity or alkalinity of a substance.  A pH of 7 is considered neutral while those levels below (0-6.9) is acidic and those above (7.1-14) is considered alkaline.  Control of pH is very important in maintaining a good water treatment program.  The recommended pH for cooling tower is 7.5-9.0, 8.5-10.5 for boilers.  pH above or below recommended levels may cause higher corrosion rates. If your tower is galvanized the pH must be no higher than 8.3.

Alkalinity:  Sometimes confused with pH, it  has nothing to do with pH levels.  Alkalinity is due to the presence of bicarbonate, carbonate, and hydrate ions.  For our purposes alkalinity consists of calcium and magnesium bicarbonate.  This alkalinity will produce CO2 when water is heated; therefore, it can cause corrosion even though the pH is neutral.  Usually alkalinity as high as 300 PPM is not a problem unless the hardness is below 10 g.p.g.  An index called the saturation index is used to determine if a specific water will cause corrosion.

P - Alkalinity, Bicarbonates, Carbonates, Hydroxides, Total Alkalinity:  Alkalinity is measured by double titration.  Titration to the Phenolphtalein end point (P - Alkalinity) measures OH- and ½ CO3;   M (total) - Alkalinity represents Bicarbonates, Carbonates and Hydroxides.  Ranges vary depending on certain variables.  The numbers are used to monitor scaling tendencies and are interrelated.

Total Hardness:  Hardness in water is caused by dissolved minerals, primarily divalent cations including calcium and manganese ions.  Because these salts are the least soluble salts, and are less soluble at higher temperatures, they are the common scale formers on the heat exchange surfaces.  Make – up water (NYC water) has approx. 20 ppm of hardness.  We limit the hardness by 200 ppm for Cooling Towers, and  400 ppm for Low Pressure Steam Boilers.

Iron:  Testing determines both the when system needs cleaning, and if excessive corrosion is occurring.  As you are aware, systems will always generate iron even with an excellent corrosion control.  For instance in a 3,000 - gallon system with only 1/1000 of an inch/year (1 mil) corrosion, over 300 pounds of rust will be generated.  The recommended level is less than one ppm of iron.  Usually high iron (above (1) one ppm) indicates excessive corrosion rates. Iron or copper in solution will cause pitting.

Chloride:  An ion, compound or salt of chloride, such as sodium chloride or calcium chloride.  We use chloride as an indicator of the cycles of concentration in a system.  This allows us to monitor the overall concentration of hardness minerals, which will indicate if enough blowdown is occurring.  By maintaining the proper levels of chlorides in a system the chance that heat exchange surfaces will be fouled by a buildup of scale is minimized.  In New York City the recommended range of chlorides is 72-90 ppm for cooling towers, 135-180 for low pressure steam boilers.  This is based on 9 ppm of chloride in the city water.  Be aware that this varies seasonally.

Molybdate:  A vital ingredient of the corrosion inhibitor solution.  The recommended range is 2-6 PPM for cooling towers.  This is also used as a tracer test to confirm the presence of other water treatment ingredients such as polymers that are included in the chemical formulation but are difficult to test.  Limits: 75-85 ppm for Chilled Water, 150-175 ppm for Hot Water Systems. Moly is best on stressed or any system where pitting corrosion is a concern. It is the best inhibitor to reduce this most dangerous type of corrosion. Many vendors have eliminated it because of cost.

Zinc:  A corrosion inhibitor for galvanized metals.  At least one (1) ppm is recommended. Often difficult to formulate with.!
 
Nitrite:  The corrosion inhibitor for Closed Systems and boilers.  The recommended level for closed systems is 400-800PPM of Sodium Nitrite.  For the low pressure boilers we maintain 1000 –1500 ppm of nitrite. This product is formulated with dispersants to aid in maintaining the cleanliness of the system and dyes to enable visual detection. Sometimes the dye hides rusty water so an iron test should always be performed when dye is used.

Specific Conductance (conductivity):  An electronic measurement of the mineral buildup in the water.  It is the inverse of electrical resistance.  The higher the mineral concentration the lower the resistance.  Recommended range varies for different systems, but we always maintain the level less than 1000 mmhos/cm for cooling towers.  The maximum of 3500 mmhos/cm at 25C without neutralization for steam boilers.

Total Dissolved Solids:  TDS levels below 900 ppm do not present a problem in residential or commercial applications.  TDS levels above 900 ppm will affect the performance of water softener in the form of hardness and iron "leakage".  All waters contain some natural sodium, and the higher the TDS, usually the higher the sodium level.

Sodium is used to regenerate a water softener and high levels of natural occurring sodium, plus that used to remove the hardness, will combine to a level high enough to partially regenerate the softener.  Thus, water with a TDS of 1500 ppm and 40 grains of hardness will cause hardness and iron leakage.

TDS is also a factor in performance or Reverse Osmosis Systems.  The R.O. membrane has limitation on TDS due to its ability or inability to carry away solids which might plug the membrane.  We limit this to 700 ppm for cooling towers and 2800 ppm for low pressure steam boilers.

Suspended Matter:  Particles which are present in the system water in suspended condition.  We monitor this to reduce the possibility of fouling.

Biological Growths:  Biological fouling in cooling systems is the result of excessive growth and development of different members of the lower forms of plant life – algae, bacteria, and fungi.  The lower the better.  The “Low” indicates good and “Very low” is excellent biological control.  Some growth is normal as cooling tower water is never sterile. We use paddle testers for easy monitoring.

Cycles of Concentration:  The number of times a total volume of water has been evaporated and replaced by fresh water.  Fresh water is considered to be one (1) cycle.  This one cycle carries a certain amount of dissolved solids, minerals, etc.  As a volume of water is evaporated, fresh water is brought into the system.  Evaporation leaves all minerals, dissolved solids etc., behind so the water becomes concentrated and these minerals will eventually plate out on areas of heat exchange unless the system is blown down.  Less than ten (10) cycles is recommended for cooling towers.  We also use this to control the dirt brought in by the air washing effect of the tower.  The maximum of 20 cycles of concentration for low pressure steam boilers.

Oxygen Scavenger:  Is a substance that will absorb oxygen in a chemical reaction.  The recommend level of sodium sulfite is 30-50 ppm.

Scale:  A deposit on a heat transfer surface resulting from precipitation of salts present in water in contact with that surface, forming a hard, dense material.  Scale is very insulating in nature.  Scale forming minerals are less soluble as temperature increases, so they will first plate out on heat transfer surfaces.

Blowdown (Bleed):  The running to waste a portion of water in a system either automatically or manually.  This will prevent over concentration of minerals and foulants.

Corrosion:  A process by which a metal undergoes a reaction with its environment resulting in a reversion to its ore.

Bacteria Counts:  Indicate bacteriological contamination of the system.  The lower the counts the better bacteria control you have.  Counts of 10000 cfu/ml are acceptable, 1000 cfu/ml are very good, 100 cfu/ml and less are excellent.  This test may not show all bacteria such those that form slimes or disease.  Specific test may be required for these.

Tolyltriazole:  The copper and brass corrosion inhibitor.  The recommended level is 1-2 PPM for cooling towers and higher in closed systems. Many vendors have discontinued its use because of cost

Phosphate:  iron corrosion inhibitor - This is added by the NYC DEP to minimize lead leaching from brass. Many also use it as part of their treatment program. It is difficult to differentiate the vendor provided phosphate from the city provided particularly at higher conductivity levels. We have seen some vendors report good phosphate levels without having added any.  Obviously this is a very low cost program for the vendor.


In our reports you will see information on Conductivity, pH, inhibitor and  iron levels, as well as other related items that the service person lists to provide an overall report on how well your treatment objectives are being met.  If all parameters are good, the corrosion process is minimized (not stopped) and operating efficiency is maximized.  We hope this overview of the terms we use as well as your customized reporting form will give you a clearer picture of our actions in the field and the reasons behind them.  If you require additional information, please do not hesitate to call.