Calculators - Further Reading

Calculators for Pool Design and Maintenance

At TFP we believe pool maintenance should be based on science and physics. There are many underlying calculations that go into TFP recommendations and advice. Below are some tools to allow you to make your own calculations and see the effects on your pool.

Pool Math

Pool Math makes it simple to track all of your Pool Test Logs and takes all of the guess work out of how much chemical you need to add.

Pool Math calculates the quantities of chemicals required for adjusting chlorine, pH, alkalinity, calcium, CYA, salt, and borates. It also calculates the Calcium Saturation Index if you log the water temperature.

You need to enable tracking of CSI, salt, borates or water temperature under the round hamburger option icon.

Pool Math also calculates the effects of adding a chemical and calculates the normalized price of bleach/chlorine so you can compare the value of products with different chlorine percentages and quantities.

The Effects of Adding Chemicals in Pool Math includes a SWG run time calculator to calculate the FC output for a given % and run time of salt water chlorine generators. You go to Effects of Adding Chemicals; Select SWG; Select which SWG you have; Put in % setting and pump run time and it will show you the FC generated per 24 hours.

Pool Water Evaporation Rates

This Water Evaporation spreadsheet will calculate the evaporation rate given air and water temperature, relative humidity, and wind. Note that this is the wind speed at the surface of the water which is usually quite a bit lower than general wind speed due to fences and the water being somewhat below ground level.[1]

For more read Evaporation of Pool Water.

Heater Run Time and Cost Calculator

This Heating Runtime and Cost spreadsheet[2] contains:

  • A Scratch Pad where you can estimate the hours needed to run the heater to achieve a desired temperature rise for a given water volume. There is a Multiplier Factor to account for variability in heating water that is subject to the elements. This is explained further in the spreadsheet.
  • A Cost Estimator where you can select the billing unit from a drop-down list, cost per billing unit, heater BTU, and number of hours the heater is run. For the number of hours, you can use either the hours calculated in the Scratch Pad or enter your own figure. The spreadsheet calculates cost by taking the cost per billing unit and dividing it by the number of BTUs in that billing unit to arrive at a cost per BTU. It then takes the cost per BTU and multiplies that by the Gross BTU output of the heater to get the cost per hour to run the heater. The cost per hour is then multiplied by the number of hours the heater is run to arrive at the Total cost to run the heater for X hours.

The spreadsheet is set up to use with Natural Gas heaters. It estimates the variable usage-based cost that appears on your bill. Fixed costs that appear on your bill are not factored into cost calculations since, by definition, a fixed cost is static and would appear on your bill as the same amount each month regardless of consumption.

When using the runtime for Heat Pumps put the Heat Pump BTU's in the Net heater BTU field instead of reducing it by 20% for natural gas heater efficiency loss.

For calculating heat pump costs vendors like Pentair has a Heat Pump Calculator to determine the appropriate size Heat Pump for your location.

This spreadsheet loads in Excel .xls 2003 format but should be saved in .xlsx format.

Natural Gas Heating Cost Calculator

The thermodynamics of heated and non heated swimming pools is quite complicated. This Swimming Pool Energy and Temperature Calculator from Neil O. Anderson & Associates makes it easy for pool builders and designers to predict the amount of energy needed to heat a pool, or to calculate the temperature of a pool at a given time during the year.

The calculator uses geographic data combined with solar and wind data to accurately calculate thermal parameters. The program also incorporates pool features such as pool covers, insulation, and wind breaks. The program output shows you cost by month to see how your monthly temperature changes affect cost.

Estimating Pool Water Gallons

If you need to get an estimate of the amount of water in your pool you can use the calculator at the bottom of the old Pool math web page. You simply enter the pool dimensions and average depth and it gives you the gallons of water int he pool.

Hydraulics 101 - Pump and Pool Spreadsheet Tools

@mas985 has developed the following spreadsheets:

  • Pool Pump Tools - Estimates pump operating points, pump energy costs and waterfall flow rates.
  • Pool Heat Transfer Tools - Estimates heat loss and gain from a full heat transfer model that includes the effects of the sun, solar panels, NG heater, heat pump, and environmental conditions. It will also estimate the amount of water lost per day/week due to evaporation. Included are tabs to estimate heat loss from pipes and how long it can take for a pipe to freeze.
  • Chemistry Calculator - Calculate chemicals required to balance pool chemistry and logs test results.

License agreement and download links can be found at the Hydraulics 101 thread.

SWG Runtime Spreadsheet

SWG Runtime Spreadsheet .png

While the PoolMath App will calculate SWG runtime and FC output, you will find the link to the SWG Runtime Calculator in the first message of the thread if you prefer a spreadsheet to the App.

You need to know the 24 hour FC output of your SWG cell at 100% to enter into the spreadsheet and the PoolMath App has a lookup for that.