Many HOA board members receive weekly pool chemistry logs long before the numbers feel intuitive. The report may include pH, free chlorine, total chlorine, alkalinity, calcium hardness, and cyanuric acid, but unless a complaint or closure forces the issue, it can be difficult to know what deserves attention.
That is entirely understandable, but these readings matter. They are among the clearest signals of whether a community pool is sanitizing properly, operating comfortably, and staying within code. This guide explains what each one means, why it matters to both residents and boards, and when a board should ask follow-up questions.
Why chemistry matters at all
Commercial pool water is a constantly changing system. Swimmers, sunlight, rain, dust, leaves, sunscreen, sweat, and other contaminants affect water balance every day. When the key measurements remain within range, the result is clear water, effective sanitation, and fewer swimmer complaints.
When they do not, the consequences may include:
- Cloudy water
- Algae
- Eye and skin irritation
- Strong chloramine odor
- Corrosion or scale
- Illness risk
- Health department citations
- Closure
Each of those outcomes can usually be traced back to one or more of the six core readings on the chemistry log.
The six numbers, in plain English
1. Free chlorine (1.0 to 5.0 ppm)
What it is: The active sanitizer available to kill bacteria and viruses.
Why it matters: Free chlorine provides the pool's immediate disinfecting power. When it falls too low, the water is not sanitizing effectively. When it rises too high, swimmer comfort declines and the pool moves outside code range.
Target range: 1.0 to 5.0 ppm, with 2.0 to 3.0 ppm as a practical target for most outdoor pools in the Chicago summer.
Signs of drift:
- Below 1.0 ppm: inadequate sanitation; the pool should not remain open in that condition
- Above 5.0 ppm: stronger odor, possible eye or skin irritation, and out-of-range readings
Who monitors it: Every service visit. During operating hours, Illinois requires testing at least twice per day.
2. Combined chlorine / chloramines (target: below 0.2 ppm)
What it is: Chlorine that has already reacted with contaminants and lost most of its useful sanitizing value.
Why it matters: Chloramines are a common source of the sharp "chlorine" odor swimmers complain about. In most cases, that smell signals insufficient effective chlorine, not excessive chlorine. The corrective action is usually shocking the pool, not reducing chlorine feed.
Target range: Below 0.2 ppm at all times. Code may allow up to 0.4 ppm, but anything near that threshold usually indicates a developing problem.
Signs of drift:
- Above 0.2 ppm: strong odor on deck, swimmer complaints, and eye irritation
- Above 0.5 ppm: the pool should generally be closed until the level is corrected
Who monitors it: Weekly full-panel testing at minimum, and more often on high-use pools during peak season.
3. pH (7.2 to 7.8)
What it is: A measure of how acidic or basic the water is. Pool water is maintained slightly basic because that is where swimmer comfort and sanitizer performance are best balanced.
Why it matters: pH is one of the fastest-changing readings in pool operation. Bather load, rainfall, and chemical feed all affect it. When pH drifts out of range, chlorine becomes less effective and swimmers feel the difference quickly.
Target range: 7.2 to 7.8, with 7.4 to 7.6 as a practical operating target.
Signs of drift:
- Below 7.2: corrosive water, eye irritation, and overly harsh chlorine activity
- Above 7.8: reduced sanitizer performance and increased risk of scale on tile and equipment
Who monitors it: Every service visit. In the Chicago summer, many commercial pools trend upward and require routine acid correction.
4. Total alkalinity (60 to 180 ppm)
What it is: The water's resistance to pH swings. It functions as a buffer for the pH reading.
Why it matters: Low alkalinity allows pH to move too quickly. High alkalinity makes pH difficult to adjust. Either condition increases chemical use and makes the water harder to manage.
Target range: 60 to 180 ppm, with 80 to 120 ppm as a practical target for most pools.
Signs of drift:
- Below 60 ppm: unstable pH, recurring chemistry corrections, and cloudy water
- Above 180 ppm: persistent scaling and sluggish chlorine performance
Who monitors it: Weekly full-panel testing. Alkalinity correction is usually gradual and may take several days.
5. Calcium hardness (150 to 1,000 ppm)
What it is: The amount of dissolved calcium in the water.
Why it matters: If calcium is too low, the water can pull minerals from plaster, grout, and tile surfaces. If it is too high, calcium deposits form on surfaces and equipment, especially inside heaters and filters.
Target range: 150 to 1,000 ppm, with 200 to 400 ppm as a practical target for most plaster pools.
Signs of drift:
- Below 150 ppm: etching, grout deterioration, and long-term surface damage
- Above 500 ppm: scale, cloudy water, filter fouling, and higher heater risk
Who monitors it: Weekly full-panel testing. Chicago-area fill water is typically calcium-heavy, so many pools trend upward over time.
6. Cyanuric acid (0 to 100 ppm; practical cap 50 ppm)
What it is: The stabilizer that protects chlorine from UV degradation in outdoor pools.
Why it matters: Without cyanuric acid, outdoor pools lose chlorine quickly in direct sun. With too much of it, chlorine becomes far less effective. That condition is often described as chlorine lock.
Target range: 30 to 50 ppm for most outdoor commercial pools. Illinois may allow higher readings, but many inspectors become concerned once levels move above 50 to 60 ppm.
Signs of drift:
- Below 30 ppm: chlorine burns off rapidly in sunlight
- Above 70 ppm: sanitizer efficiency drops and partial drain-and-refill may be required
Who monitors it: Weekly. Cyanuric acid does not meaningfully decline on its own; it usually falls only when water is drained and replaced.
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How to read your weekly chemistry log like a board member
Most HOA boards do not need to manage chemistry directly. They do need to recognize whether the log looks normal and whether trends deserve follow-up.
Each week, check four things:
- Are free chlorine readings consistently between 1.0 and 5.0? If yes, the pool is likely sanitizing properly.
- Is combined chlorine consistently below 0.2? If it trends upward for several days, something needs attention.
- Is pH staying between 7.2 and 7.8? If it drifts in the same direction week after week, the feeder may be miscalibrated or alkalinity may be out of range.
- Are the full-panel numbers stable over time? Watch alkalinity, calcium hardness, and cyanuric acid for slow but meaningful changes.
For most boards, a periodic review of the trend lines is enough, provided a qualified technician or CPO is actively managing the pool.
Who is actually responsible
In Illinois, the Certified Pool Operator (CPO) associated with the facility is the person legally accountable for pool chemistry. That may be:
- A CPO employed by your pool management company
- A CPO on the HOA's maintenance staff
- A contracted CPO who visits the site periodically
If your board cannot identify the responsible CPO, address that immediately with your pool management company. A clean-looking pool does not replace the compliance requirement.
For the full compliance picture, see our IDPH commercial pool compliance checklist.
When should a board step in?
Most chemistry issues belong with the technician and the CPO. Boards should become directly involved when there is a pattern, a closure, or a recurring member-facing problem.
Three common escalation points are:
- Repeated combined chlorine readings above 0.4 ppm. This usually indicates a systemic problem, such as under-dosing, equipment issues, or unusually heavy bather load.
- Closures caused by chemistry. More than one chemistry-related closure in a season warrants a clear explanation and corrective plan.
- Recurring complaints about eyes, skin, or odor. If the free chlorine number appears normal but complaints continue, combined chlorine is often the more relevant issue.
In most other situations, the board's role is oversight: confirm that the chemistry is being managed properly and that issues are being escalated when necessary.
Training your own staff
If your HOA wants an on-site staff member who understands these readings for backup coverage, incident response, or operational continuity, we run Certified Pool Operator (CPO) classes monthly at our Schaumburg office. The course is two days, includes the exam, and covers both water chemistry and regulatory compliance.
Need more confidence in your weekly chemistry reporting?
If your community wants professional weekly pool chemistry service with reliable logging, clear reporting, and prompt escalation when numbers drift, see our weekly pool maintenance service or choose your suburb from the Chicagoland coverage page. Our certified technicians can maintain the log, post results to your board portal, and notify the property manager or board contact promptly when corrective action is needed.
