Do you have a traditional pool heater?
By skimping on $40.00 worth of chemicals to adjust and control the pH level of your pool water, you could cost yourself hundreds of dollars...maybe even a couple thousand dollars if you need a new heater.
Low pH levels over time will lead to a condition known as acidic water, which will destroy the copper heat exchanger in a heater if that pH level is left low. That heat exchanger is a very important and very expensive part. Depending on your local market, the brand of the heater, the BTU output of the heater, the service technician you hire and the duration of the service call to replace a heat exchanger, you will be left with a $500.00 - $900.00 invoice (maybe even higher). And, if the cabinet of the heater as well as the condition of other internal parts dictate that it is best to just replace the heater, you will be left with an invoice of at least $1,500.00 - $2,000.00 (maybe even higher), also depending on your local market, the brand of the heater, the BTU output of the heater, the service technician you hire and the duration of the service call to replace the heater.
Heaters are expensive. Whether you have a natural gas heater or a propane heater, low pH levels can and will destroy the copper heat exchanger, which essentially ruins your expensive heater until you spend even more money to have it repaired or replaced.
If you have a pool heater, then consistently maintaining an ideal pH level is of extreme importance. To be clear, this is not an invitation for you to neglect pH tests and adjustments if you do not have a pool heater.
You can read the Pool Manual for additional information about pool chemicals, pool heaters, water chemistry, pH and its relation to pool heaters.