How Often Should Commercial Pool Water Be Tested?

Under the CDC's Model Aquatic Health Code (MAHC), free chlorine, combined chlorine (or total bromine) and pH are tested before opening each day (5.7.5.1). While the pool is open, you test free chlorine (or bromine) and pH again every 2 hours with a hand-fed system, or every 4 hours with an automatic controller (5.7.5.2, 5.7.5.3). Your state's code may change those numbers, so check which version it adopted.

What does CDC say about testing frequency?

CDC's page on operating public pools gives a short version. It says to test pH and disinfectant levels at least twice per day, and hourly when the pool is in heavy use.

The 2024 MAHC, section 5.7.5, is more detailed. It sets intervals by feed system: manual (no automated controller) or automatic (a controller that doses from its own readings).

What does the full schedule look like?

Here is the MAHC 2024 schedule in one table:

Test	How often (MAHC 5.7.5)
Free chlorine, combined chlorine (or total bromine), and pH	Before opening every day
Free chlorine (or bromine) and pH, manual feed system	Every 2 hours while open
Free chlorine (or bromine) and pH, automatic feed system	Every 4 hours while open
In-line ORP reading, if installed	Recorded at the same time as each chlorine and pH test
Water temperature, heated pools	Recorded at the same time as each chlorine and pH test
Total alkalinity	Weekly
Calcium hardness	Monthly
Cyanuric acid (CYA), if used	Monthly, and 24 hours after adding CYA
CYA, if stabilized chlorine is the main disinfectant	Weekly or more often
Saturation index	Monthly
Total dissolved solids	Every 3 months
Salt, with a salt chlorinator	At least weekly or per the maker's instructions
Copper and silver, if that system is used	Daily

Our cyanuric acid guide covers the CYA tests and limits.

How do you turn the rules into a daily plan?

Make a sheet for each pool, not one rule for the whole company. Two pools on the same site can have different feed systems, so they can have different intervals.

A worked example: say a pool opens at 9 a.m. and closes at 9 p.m. with an automatic controller. Under the MAHC, staff test before opening, then around 1 p.m. and 5 p.m. A pool with manual feed and the same hours would test before opening at 9 a.m., then at about 11 a.m., 1 p.m., 3 p.m., 5 p.m. and 7 p.m.

Your planning sheet could include:

• The pool name and its feed system.
• Each required test and its source (local code section or MAHC section).
• Test times written as clock times, not "every few hours".
• The person assigned and the backup contact.
• Where results are recorded.
• What to do if a result is late, unclear, or out of range.

How should the schedule handle busy periods?

CDC's operating page says to test hourly during heavy use. Ask the qualified operator to write down what counts as heavy use at your pool, the extra test, and who does it. "Test more when busy" leaves the guard to guess.

If staff cannot do the tests and still keep their safety duties, such as watching the water, tell the manager. Check who is free for each test before you approve the schedule.

What should happen at a shift change?

Record when the last test happened and where its results are. List any open concern and name who does the next test.

The next shift should not have to search a group chat to learn whether the pool is open. Keep any closure decision and the operator's instructions with the water record. For a sample layout, see what belongs on a water test log. Use the same test names on the log and the schedule.

What if a test is missed or the result looks wrong?

Record what happened and tell the supervisor. Never invent a value or write a test time that did not happen. The next test should carry its real time.

Treatment and closing decisions stay with the qualified operator.

Keep the missed test and the response in the same record. The manager can then see if the cause was unclear ownership, a missing kit, or too few staff.

How do you make results useful after the test?

A result only helps if staff know the limits it should fall within. Our guides to the commercial pool chlorine range and commercial pool pH range explain where those limits come from.

Poolean records water readings and test photos, including entries made without a signal that upload when the connection returns. See the water testing features or book a 30-minute call to review that process.

The short version

• Under the CDC's model code, test free chlorine, combined chlorine and pH before opening every day.
• Then test free chlorine and pH every 2 hours (manual feed) or every 4 hours (automatic feed) while open.
• Test alkalinity weekly and calcium hardness monthly, plus the other items in the table.
• Assign each test to a person and record real times and results.