The above is a question I find myself asking customers in our store many times a day. When they answer that they do not know, I find these questions running through my mind:

1)  How do you know how much chemicals to add to your pool?

2)  How do you know how many hours a day to run your pool pump?

3)  Do you know if you are spending more than you should on energy and chemicals?

Likewise, the reason I am asking them in the first place how many gallons (or the size of their pool) is because they are asking me the following:

1)  Why is my motor running hot?

2)  I need to replace my pump what size do I need?

3)  I want better flow (they mean pressure usually which should not be confused with flow), can I increase the size of my pump?

4)  I want a new filter but don’t need to replace my pump.  What size and type can I get?

5)  How much chlorine or other chemical should I add to my pool?

     Everything we do on a swimming pool or spa is dependent on calculations. The entire design of the pool starts with calculations to properly size the circulation system or heart of the pool.  This determines how many returns, suction inlets, lights, size of pipe, how much pipe and so on.

     The equipment of your pool is the center of activity for your pool circulation.  To get the water into your pool and back to the equipment in a manner that will keep your pool healthy is based on hydraulics.  We determine the gallons in the pool, determine what our turnover rate should be (how many times the water is filtered in a day), the flow rate in gallons per minute and then calculate the resistance to be able to determine the proper pump size and match it to the filter type in order to achieve this.

     Heaters, chlorine generators, and other equipment will not work correctly if the flow rate is less than the minimum required or over the maximum allowed. 

     Next we use the pool gallons and dosage directions to calculate chemical dosages so that we do not over dose or under dose the pool with chemicals. This will require calculations from the testing of the water and the amount needed to raise or to lower to adjust to accepted levels of given parameters.

     So many times we find in our service department that someone has purchased equipment that they put on a pool will not function simply because someone did not do the math to find the flow rate required.  Likewise adding chemicals without calculating how much is needed can be harmful and a waste of money if the results are not reached as expected.