US and Metric System relations and ppm vs mg l

Transcription

1 Does the idea of using the metric system irritate you? Are you just happy with the US system of weights and measures? Are you comfortable with measurements like inches, feet and yards; Volume measurements like fluid ounces, cups, pints, quarts and gallons; Weight measurements like ounces and pounds? Feel like the metric system is a nightmare because you have no idea how many liters in a gallon, feet in a meter, grams in an ounce or milliliters in a quart? Well the metric system is only a nightmare when you are trying to convert a US measurement into a metric measurement or vice versa. For instance if your car speedometer only read kilometers per hour and the speed limit signs were now only in KPH (kilometers per hour) then it would be easy. If the grocery store only sold hamburger by the grams, you would quickly determine that you need maybe 150 grams per burger and buy that amount. Metric Basis and Relations = = = 1 ml = 1 cm 3 = 1 g = 1 Calorie In metric 1 ml (milliliter) of water occupies 1 cc (cubic centimeter), weighs 1 g (gram) and requires 1 Calorie of energy to heat up by 1 C (Celsius) which is 1 percent of the difference between freezing and boiling. = = = = 1 L = 1 dm 3 = 1 Kg = 1 Kilo Calorie 1,000 ml = 1,000 cm 3 = 1,000 g = 1,000 Calorie Copyright 2015 Lowry Consulting Group, LLC Page 1 All rights reserved. Duplication not permitted without written permission.

2 The Metric System is all orderly and logical and makes converting either direction from smaller to larger a matter of dividing or multiplying by 10, 100 or 1,000. Not so for the US weights and measures. The US system does not relate to any of these quantities and in fact, the volumes, space, weights and energy don t relate at all. Here is a graphic illustration showing the relationship in the same manner as above but for US. US Basis and Relations = = 1 fl oz = inch 3 = oz = BTU = = = 1 Qt = cube in = lbs = BTU 32 fl oz = In 3 = oz = BTU Other US Constants, Factors & Conversions = 1 cubic inch (inch 3 ) of water = fl oz (fluid ounces) Copyright 2015 Lowry Consulting Group, LLC Page 2 All rights reserved. Duplication not permitted without written permission.

3 = = = 1 cubic foot of water = lbs = gallons = 1 oz (weight) of water = fl oz (fluid ounces) = Please Note: The weights and measures used for Metric and US are based on water at 4 C or 40 F and 1 atm (atmosphere) of pressure. Water weighs slightly more at 80 F lbs/gal at 4 C versus lbs/gal at 70 F and lbs/gal at 80 F. It is common practice to use 8.33 or 8.34 lbs/gal when converting gallons to lbs. 1 gallon of water = lbs per gallon = 1 BTU = 1,055 joules 1 BTU raises 1 lb of water by 1 F and is equal to 1,055 joules Copyright 2015 Lowry Consulting Group, LLC Page 3 All rights reserved. Duplication not permitted without written permission.

4 The US weights and measures is a mess when you want to do calculations. It isn t any wonder pool service techs, pool stores, pool operators and residential pool owners have problems trying to figure out pool gallons and adding chemicals in parts per million. Pool Volume and PPM Calculations in US Measurements Determining pool volume requires making measurements in feet and inches in three dimensions (length, width and depth) to get cubic feet of water and then converting cubic feet into gallons. Then to add chemicals in ppm (parts per million) which is a weight to weight relationship, requires converting gallons into pounds and then calculating how many pounds of a chemical is required to attain a ppm. Then possibly converting the weight of the chemical to be added back into a volume if it is a liquid and taking into consideration the concentration of the chemical. Here is an example of all the calculations needed to add 2 ppm of chlorine using cal hypo 65 % to a pool that measures 34 feet 6 inches by 15 feet 8 inches with a shallow end depth of 30 inches and deep end depth of 5 feet 6 inches. Determine Cubic Feet in Pool Before we can multiply the three dimensions (length, width and dept) together we have to convert inches into decimal equivalents of a foot. This is because we want to determine cubic feet. To get the decimal equivalents, we divide inches by 12 inches in a foot. Length = 34 feet 6 inches = 0.5 so we have 34.5 feet Width = 15 feet 8 inches, 8 12 = 0.75 so we have feet Shallow End depth = 30 inches, = 2.5 feet Deep End Depth = 5 feet 6 inches, 6 12 = 0.5 so we have 5.5 feet To determine the pool s average depth, we add the shallow end depth to the deep end depth and divide by 2. So 2.5 feet feet = 8 feet. Dividing 8 by 2 we get 4 feet average depth. Copyright 2015 Lowry Consulting Group, LLC Page 4 All rights reserved. Duplication not permitted without written permission.

5 To get pool volume in feet we multiply length times width times average depth (L W Avg D) = 2,173.5 cubic feet (ft 3 ) Now to get pool volume in gallons, we have to convert cubic feet of water into gallons. Determine Gallons From Cubic Feet in Pool From above, we know there are gallons in a cubic foot of water. (You can round this number off to 7.48 or even 7.5 and the result we be close enough for pool work.) 2,173.5 ft gallons/ft 3 = 16,258.9 gallons Approximating the dimensions and conversion, you would get = 16,800 gallons. This is pretty close and does not require that accuracy. In addition, consider this, 1 inch of water in this pool is almost 350 gallons, so we are close at 16,800 gallons. Calculating PPM From Gallons In all, we have made 6 calculations to get gallons. And it is not over yet because we want to add 2 ppm of free chlorine to this pool using liquid bleach at 6%. PPM is a weight to weight relationship - 1 pound in a million pounds is a ppm or 1 oz in a million oz is a ppm. It is not 1 gallon in a million gallons because all liquids have a different weight per gallon or density. First convert gallons into pounds. One gallon of water weighs 8.33 lbs. So multiplying 8.33 times gallons will give us lbs ,258.9 = 135,436.6 lbs of water Second divide lbs of water by 1,000,00 to get the number of lbs in 1 ppm 134, ,000,000 = lbs in this pool is 1.0 ppm Copyright 2015 Lowry Consulting Group, LLC Page 5 All rights reserved. Duplication not permitted without written permission.

6 Third convert decimal pounds into ounces. There are 16 oz in 1 pound. We multiply 16 by the ppm decimal pounds. Water Coach = oz. This means that oz by weight of 100% pure chemical added to this pool will be 1.0 ppm. But we have said that we are using a cal hypo 65 % chlorine. We have to divide the oz by 0.65 to get the amount needed = 3.33 oz So 3.33 oz of cal hypo 65 % will give us 1.0 ppm in this pool However, the chlorine to be added is 2.0 ppm oz 2.0 ppm = 6.66 oz So 6.66 oz of cal hypo 65 % will give us 2.0 ppm in this 16,258.9 gallon pool. To review, we made 6 calculations to get gallons and 6 more calculations to get the amount of chemical needed to add a dose in ppm. Pool Volume and MG/L Calculations in Metric Metric is Easier - But It Is Not a PPM, It Is a MG/L PPM is a weight to weight relationship. In metric we use milligrams per liter (mg/l). It is still a weight to weight relationship. There are 1000 milligrams (mg) in a gram and there are 1000 milliliters (ml) in a liter. So 1,000 1,000 = 1,000,000. Therefore it is 1 mg/l. Here is an example of all the calculations needed to add 2 mg/l of chlorine using cal hypo at 65% to a pool that measures 10.4 meters by 5.6 meters with a shallow end depth of 0.8 meters and deep end depth of 2.0 meters Determine Cubic Meters in Pool Copyright 2015 Lowry Consulting Group, LLC Page 6 All rights reserved. Duplication not permitted without written permission.

7 The measurements are already in meters with decimals so there is no need to convert anything. Exact Calculation Practical Estimate Length = 10.4 meters Length = 10 meters Width = 5.6 meters Width = 5 meters Shallow End Depth = 0.8 meter Shallow End Depth = 1 meter Deep End Depth = 2.0 meters Deep End Depth = 2 meters Avg Depth = ( ) 2 = 1.4 meters Avg Depth = (1 + 2) 2 = 1.5 L W Avg D = cubic meters L W Avg D = cubic meters = 81,536 cubic meters (mts 3 ) = 75 cubic meters (mts 3 ) Now to get pool volume in liters, we have to convert cubic meters of water into liters. If you can do some simple multiplication in your head, you can estimate cubic meters. Estimate that the pool is 10 by 5 by average depth of 1.5. And = 75. Determine Liters From Cubic Meters in Pool From Page 1 we know there are 1,000 liters in a cubic meter (mt 3 ) of water mt 3 1,000 liters/mt 3 = 81,536 liters [You can just add 000 (three zeros) to mt 3 to get liters.] Calculating MG/L From Liters We have only made 2 calculations to get liters. We want mg per liter (mg/l) so 81,536 mg in 81,536 liters = 1 mg/l There are 1,000 mg in 1 g (gram) So 81,356 mg 1,000 mg/g = grams and is 1 mg/l in a 81,536 liter pool Quick tips: Copyright 2015 Lowry Consulting Group, LLC Page 7 All rights reserved. Duplication not permitted without written permission.

8 The number of cubic meters is also the amount in grams for 1 mg/l If the pool is mt3, g is 1 mg/l and if the pool is 75 mt3, 75 grams (g) is 1 mg/l Add 000 to cubic meters or move the decimal point 3 places to the right to get liters If the pool is mt3, it has 81,356 liters and if the pool has 75 mt3 it has 75,000 liters. If you have a 75 mt3 pool, there are 75,000 liters and 75 g is 1 mg/l Calculting 2 MG/L Chlorine Dose Adding 2 mg/l of chlorine to this pool using cal hypo 65 %. We already know that we will need grams to get 1 mg/l. but that assumes 100% chlorine and it is for 1 mg/l. Divide grams needed for 100% by percent active chlorine in chlorine product Cal hypo is 65 % available chlorine so we need to divide the g by = g Multiply grams needed for 1 MG/L by 2 to get 2 MG/L The g is the amount needed for 1 mg/l and we want 2 mg/l = g So g of cal hypo 65 % will give us 2.0 ppm in this 81,536 liter pool. Metric System Is Easier But the US Will Not Be Switching Soon The metric system is easier for calculations but the US has a long history of using the American measurements. weights and volumes. It doesn t appear that the US will be switching to metric any time soon either. I heard in the 1960s that in 10 years we would be using metric. More than 50 years later and we are still using the US system. We are still going to have to calculate ppm the old fashioned way. However,there are some short cuts, tips, tricks and calculators that make chemical dosage determination easier. Copyright 2015 Lowry Consulting Group, LLC Page 8 All rights reserved. Duplication not permitted without written permission.

9 Tips, Tricks and Shortcuts Pool Sizes The average pool has about 17,000 gallons ± 2,000 gallons depending on depth. The average pool has about 30,000 gallons ± 2,000 gallons depending on depth. 1 PPM of Chlorine Increase 1 ppm of chlorine in 15,000 gallons using liquid chlorine12.5% is about 15 fl oz or 1/2 quart. 1 ppm of chlorine in 15,000 gallons using liquid bleach 6% is about 32 fl oz or 1 quart. 1 ppm of chlorine in 15,000 gallons using cal hypo 65% is about 3 oz. 1 ppm of chlorine in 120,000 gallons is about 1 gallon of liquid chlorine 12.5% or 2 gallons of 6%. 1 ppm of chlorine in 120,000 gallons is about 1.5 lbs of cal hypo 65%. CYA Increases Each 10 ppm of chlorine added by trichlor increases cyanuric acid by 6 ppm. Each 10 ppm of chlorine added by dichlor increases cyanuric acid by 9 ppm Alkalinity Increase 10 ppm increase to alkalinity is about 2 lbs of sodium bicarb per 15,000 gallons Alkalinity Decrease 10 ppm decrease to alkalinity is about 32 fl oz or 1 quart of muriatic acid (31.45%) per 15,000 gallons. 10 ppm decrease to alkalinity is about 3 lbs of dry acid per 15,000 gallons. The Easy Chemical Dosage Chart On the next page is The Easy Chemical Dosage Chart. It is a very accurate method for determining the exact amount of any chemical for any size pool. To use it follow these steps. 1. Find the chemical you are going to use and locate the amount from the Amount Needed column. Insert this amount into Box A. Example: Liquid Chlorine 12.5% is fl oz. 2. Divide the gallons in pool by 10,000 and insert this amount into Box B. Example: 15,000 10,000 = Write the amount in ppm that you are increasing or decreasing in Box C. Example 2 ppm increase. 4. Now multiply Box A Box B Box C. Example: = fl oz or about 1 quart. Copyright 2015 Lowry Consulting Group, LLC Page 9 All rights reserved. Duplication not permitted without written permission.

10 Copyright 2015 Lowry Consulting Group, LLC Page 10 All rights reserved. Duplication not permitted without written permission.