FACTS AND FORMULAS

Volume calculations


Length x width x average depth x 7.5 = volume (in gallons) of square or rectangular pool 

3.14 (pi) x radius squared x average depth x 7.5 = volume (in gallons) of a round pool 

0.45 x (A+B) x length x average depth x 7.5 = volume (in gallons) of kidney or irregularshaped pool 
Negative Edge Basin Sizing


Basin Width= square root of (.25 X Area of the pool / Length of the weir wall) 

Basin Depth= Basin Width + 1.75’ 
Measurements


7.5 gallons in each cubic foot of water 

1 inch = 0.0833 feet 

Radius = diameter divided by 2 

1 gallon of water weighs 8.3 pounds 

1 gallon of chlorine weighs 10 pounds 

16 ounces dry weight = 1 pound dry weight 

128 ounces liquid = 1 gallon 

8 ounces liquid = 1 cup liquid 

100 watts = 1 kilowatt 

1 milliamp = 0.001 amp (30 milliamps will cause muscle contractions) 

1 psi = 2.31 feet of head (resistance) 

1 psi  28 inches water column pressure (WCP) 

1 inch of mercury = 1.13 feet of head 

1 micron = onemillionth of 1 meter = 0.0000394 inches (the human eye can detect objects a small as 35 microns) 

1 grain of table salt = 100 microns 

3/4 volt of 1 volt = 750 millivolts = 0.75 volts 

1 BTU (British Thermal Unit) is the amount of heat required to raise 1 pound of water 1°F 

1 therm (measurement of gas supply) = 100,000 BTU per hour 

1 gallon of fuel oil = 140,000 BTU 

1 kilowatt = 3412 BTU 

1 gallon of fuel oil = 140,000 BTU 

1 ton (heat pump rating) = 15,000 BTU 

A typical bather displaces 2 cubit feet of water 

1 gallon of fuel oil = 140,000 BTU 

1 hp = 746 watts 
Chlorine Comparison Chart

Product Form 
PH Stability 
Available Chlorine 
Common 
C1_{2} gas 
Low 
100% 
Gas 
very unstable 
Sodium hypochlorite 
13+ 
12.5% 
Liquid 
unstable 
Calcium hypochlorite 
11.5 
65% 
Dry granular 
stable 
Dichlor 
6.8 
60% 
Dry granular 
very stable 
Trichlor 
3.0 
90% 
Tablet (or granular) 
very very stable 

Effectiveness Comparison


1 pound C1_{2} gas = 1 gallon sodium hypochlorite = 1.5 pounds calcium 

Hypochlorite = 1.75 pounds dichlor = 1.15 pounds trichlor = 2.8 pounds lithium hypochlorite 
Cost Comparison


Sodium hypochlorite = 2 times the cost of chlorine gas 

Sodium hypochlorite = 2 times the cost of chlorine gas 

Calcium hypochlorite = 3 times the cost of chlorine gas 

Dichlor = 5 times the cost of chlorine gas 

Trichlor = 3 times the cost of chlorine gas 

Lithium = 5 times the cost of chlorine gas 
95% of chlorine in water can be lost on a sunny day in two hours (without stabilizer).

Amount of product required to obtain a change in 1000 Gallons of Water

Item 
Raise or Lower 10 ppm 
Product 
Product Amount Required (dry weight unless otherwise noted) 
Calcium hardness 
Raise 
Calcium Chloride 
2 ounces 
Total Alkalinity 
Raise 
Bicarb of Soda 
2.5 ounces 
Total Alkalinity 
Lower 
Sodium Bisulfate (dry acid) 
2.5 ounces 
Total Alkalinity 
Lower 
Muriatic Acid 
1/4 Cup (Liquid) 
Stabilizer 
Raise 
Cyanuric Acid 
1.5 ounces 

Amount of chlorine needed to raise residual in 1000 Gallons of water by 1 ppm (multiply results by 30 for super chlorination procedures).

Availability of Product (Percent) 
Product Amount 
12 
1/8 Cup (Liquid) 
50 
1/4 Ounce (dry weight) 
80 
1/6 Ounce (dry weight) 

Standards


Water may not move at more than 8’ per second through copper pipe. 

Water may not move at more than 7’ per second through PVC (Some pipe manufacturers will not warranty over 5’ per second do to concerns over water hammer.) 

Water may not move at more than 6’ per second through any type of suction pipe. 
Conversion Table

Gallons to Liters 
Gallons x 3.785 = Liters 
Liters to Gallons 
Liters x 0.2642 = Gallons 
Ounces to Milliliters 
Ounces x 29.57 = Milliliters 
Milliliters to Ounces 
Milliliter x 0.0338 = Ounces 
Inches to Millimeters 
Inches x 25.4 = Millimeters 

Data


Normal rotation speed of a pump motor is 3450 rpm (revolutions per minute). On twospeed pumps, the low speed rotates at 1750 rpm. 

Alternating current (ac) in the United States runs on 60 hertz (cycles). In Europe and many other foreign countries, it runs at 50 hertz. 

PVC plumbing is designed to carry water at temperature of less than 100°F 

CPVC plumbing is designed to carry water at temperatures above 100°F. 

Head created by various plumbing and equipment components: 


A 11/2” x 90° elbow = 7.5 feet of straight 11/2” pipe 

A 2” x 90° elbow = 8.6 feet of straight 2” pipe 

A 11/2” x 45°elbow = 2.2 feet of straight 11/2” pipe 

A 2” x 45° elbow = 2.8 feet of straight 2” pipe 

Filters create 5 to 7 feet of head 

Heaters create 8 to 15 feet of head 


Sand filters strain particles as small as 60 microns 

Cartridge filters strain particles as small as 20 microns 

DE filters strain particles as small as 7 microns 

A 1 pound coffee can holds 1/2 pound of DE 

1 pound of DE will coat 10 square feet of filter grid area. 

Sand filters are designed to use #20 silica sand 

Electricity supplied to an electronic ignition pilot is 10,000 to 20,000 volts 

The chemical processes when chlorine (in any form) is added to water
C12 (chlorine) + H2O (water = HC1 (muriatic acid) +HOCI (hypochlorous acid)
HOC1 = H+ + OC12 (a positive ion of hydrogen and a negative ion of hypochlorite)
At pH 7.2 = 80% killing HOC1 +20% useless OC1
At pH 8.0 = 20% killing HOC1 + 80% useless OC1 

Urine and perspiration = ammonia 

One active swimmer produces approximately 1 quart of ammonia per hour 

Liquid chlorine is sold in a solution of 10 to 15 percent strength 

Pools must turn over in 6 hours 

Spas must turn over in 1/2 hour 

Wading pools must turn over in 1 hour 
Filtration Standards

Filter Style 
Maximum Flow (gpm/sq. ft.)
Minimum Backwash Flow (gpm/sq.ft.) 
Highrate sand 
15 
15 
DE 
2 
2 
Cartridge 
0.375* 
No Backwash 

*Note that cartridge filters are rated at 1 gpm/square foot maximum flow rate on most residential applications and the more stringent 0.375 gpm/square foot on commercial installations


Rapid sand filters are designed for flow rates of less than 3 gpm 

Highrate sand filters are designed for flow rates of 5 to 20 gpm 

Highrate sand filters are designed for flow rates of 5 to 20 gpm 

The normal filter operating pressure differential (between incoming pipe and outgoing) is between 2 and 4 psi. When it reaches 10 psi, the filter must be cleaned. Expressed another way, if you know the normal operating pressure of your filter (as observed on the pressure gauge), you must clean the filter when the pressure is more than 10 psi higher. 

Water flow must not exceed 100 gpm through 11/2” heater plumbing 

Water flow must not exceed 125 gpm through 2” heater plumbing 

Water flowing out of a heater should not be more than 10°F warmer than the water flowing into the heater 

Pool water should not exceed 82°F 

Spa water should not exceed 104°F 

The on/off switch of a millivolt heater must not be located more than 20’ from the heater 
Heater Installations


The rear and nonplumbed sides must have a least 6” of clearance 

The plumbed side must have a least 18” of clearance 

The front must have at least 24” of clearance 

The top must be at least 5 feet below (and 4 feet horizontal distance) any window, door or vent 

PVC gas lines must be buried at least 18” below ground (12 inches below concrete) 

Metal gas lines must be buried at least 12” below ground (6 inches below concrete) 
Recreational Water Chemistry Parameters

Chlorine Residual 
1.0 to 3.0 ppm 
Total Alkalinity 
80 to 150 ppm 
pH 
7.4 to 7.6 
Hardness 
200 to 400 ppm 
Total Dissolved Solids 
Less than 2000 ppm 
Cyanuric Acid 
30 to 80 ppm 

FORMULAS


75% of the surface area of a pool is the required surface area of solar panels to adequately heat the pool 

Each spa jet requires flow of 15 gpm 

Each spa jet requires 1/4 hp from the pump and motor 

To estimate the horsepower of a blower: 


1 hp = 6.5 amps at 110 volts = 3.25 amps at 220 volts 

2 hp = 13 amps at 110 volts = 6.5 amps at 220 volts 


Volts x amps = watts 

Heater BTU output rating divided by (gallons x 8.33) = degrees temperature rise/hour 

Breakpoint chlorination method (for every 20,000 gallons of water): 


1 gallon of anhydrous ammonia + 8 gallons liquid chlorine 


Leak water loss conversion inches to gallons 


Water loss in inches x (Surface Area divided by 100) x 62.5 = loss 
