Knowing enough to ask the right question
Green water is algae, and algae means the chlorine dropped somewhere along the way. The fix is a shock treatment, a hard brushing, the filter running around the clock, and then finding whatever let the chlorine fall in the first place. Cloudy water looks similar from the deck and is a different problem entirely, usually a filter one. None of this is yours to fix. Knowing the likely cause is what lets you ask the pool company a sharp question, weigh the answer, and tell a fifteen-minute correction apart from a real repair.
Below are the seven problems community pools hit most often, what causes each, and what resolving it looks like.
1. Cloudy water
What you see: The water loses its clarity and turns hazy or milky, sometimes overnight after heavy use.
Common causes: Poor filtration, unbalanced chemistry (often high pH), insufficient chlorine, or a heavy bather load overwhelming the system. Fine particles stay suspended instead of being filtered out.
Test and rebalance the water first, then check that the filter is clean and running enough hours a day, and add a clarifier if the particles are too fine for the filter to catch on its own. When the haze survives a rebalance, the filter is the suspect — undersized for the pool, overdue for cleaning, or on its way out.
Water stays this clear when the filter is clean and runs enough hours a day against balanced chemistry. Cloudiness that persists after rebalancing usually points at the filter rather than the chemicals.
2. Algae
What you see: Green (most common), or the more stubborn mustard/yellow and black-spot varieties. The water or surfaces take on a slick, colored film.
Common causes: Low chlorine, poor circulation, low stabilizer letting sun burn off chlorine, or warm water plus heavy use. Algae blooms fast when sanitizer drops even briefly during a heat wave.
Shock the pool with a heavy chlorine treatment, brush the surfaces (algae clings), run the filter continuously, and correct whatever let chlorine fall in the first place. Black and mustard algae are far harder to kill than green and may take repeated treatments. Steady chlorine and good circulation cost a community far less than fighting an established bloom.
3. Chemistry that won't hold
What you see: pH and chlorine bounce around, the water irritates eyes and skin, or the pool company is constantly chasing the numbers.
Common causes: Low total alkalinity is the usual culprit. Without that buffer, pH swings wildly. Very high or very low stabilizer, or a malfunctioning chemical feeder, can also make chemistry unstable.
Get alkalinity into its band first, because stable pH usually follows it there. Then check the stabilizer level and the feeder's calibration. Chemistry that stays a fight week after week is often an equipment problem wearing a chemistry costume, and the two usual culprits are a sensor that has drifted out of calibration and a feeder dosing more or less than it reports.
4. Circulation and pump problems
What you see: Weak flow, a noisy pump, air bubbles at the returns, or the pump losing prime and shutting down.
Common causes: A clogged pump or skimmer basket, a dirty filter, a leak on the suction side letting air in, or an aging pump motor near the end of its life.
Clear the baskets and clean or backwash the filter first, since many "pump problems" turn out to be a clog. Air bubbles usually mean a suction-side leak to find and seal. A pump that's loud, running hot, or repeatedly failing is likely worn out and headed for replacement, which is a planned expense worth anticipating.
5. Staining and scaling
What you see: Discoloration on the plaster (brown, green, or gray stains) or a rough, crusty white buildup at the waterline.
Common causes: Stains often come from metals in the water (from fill water or corroding equipment) or organic debris left too long. Scaling is calcium deposit, driven by high calcium hardness and high pH.
Metal stains usually take a stain treatment plus a sequestering agent that holds the metals in solution afterwards. Scaling means correcting calcium and pH, and sometimes cleaning the deposits off by hand. Either one coming back year after year is a water-balance problem the treatments were only ever masking, so fix the chemistry and the symptom stops returning.
6. Leaks
What you see: The water level drops faster than evaporation explains, the auto-fill runs constantly, or there's persistent wet ground near the equipment pad.
Common causes: Cracked plumbing, a failing pump seal, deteriorated fittings, or a crack in the pool shell itself. Some evaporation is normal in hot weather, so the trick is distinguishing normal loss from a true leak.
A simple bucket test confirms whether the loss exceeds evaporation. Real leaks then have to be located. Equipment-pad leaks are often visible and fixable. Underground plumbing and shell leaks need specialized detection and can be significant repairs. Ignoring a leak wastes water, chemicals, and heat, and can undermine the deck or structure over time.
7. Deck, fence, and safety-equipment wear
What you see: Cracked or heaving decking, a gate that no longer self-latches, faded signage, or missing rescue equipment.
Common causes: Ordinary weathering and heavy use over seasons. These degrade quietly and get overlooked because they're not "the water."
These are the items an inspector looks at hardest, and a plaintiff's attorney looks at them just as hard. A self-closing, self-latching gate is your primary drowning-prevention feature and must work every single time. Keep signage legible and rescue equipment present and unobstructed. Deck repairs range from minor patching to reserve-level replacement, so catch them early and plan the big ones.
The pattern behind most problems
Six of the seven trace back to one of two things: chemistry nobody held steady, or equipment nobody maintained or replaced on schedule. What prevents both is dull and cheap — competent service on a regular interval, plus an honest end-of-season assessment that names what is wearing out. A pool on that footing rarely surprises anybody. A neglected one lurches between crises, and each crisis costs more than the year of attention it replaced.
Getting ahead of it
Your job on this is narrower than it looks. Keep a capable pool company on the water at a steady interval, and make sure that company tells you what is wearing out before it fails. Chemistry read and logged every visit, the filter cleaned on a schedule, the pump replaced the winter before it dies rather than the July it dies. Do that and the seven problems above stay off the agenda.
Green water, a heater that quits in May, a drain cover past its date — each one is easier to catch when the readings sit somewhere a board can scroll. That is what VendoRFP holds. You post the pool work, local pool companies propose on it, and your board reads the proposals side by side before it picks one. Your community signs with the pool company it picked. Three documents have to be current before a company can propose: general liability, workers' compensation, and the CPO card the pool trade requires. A person here opens each certificate and verifies the limits and the expiration date against what your community requires, on a 30-day renewal window for the insurance lines. Each company invoices you in its own name. A season of chlorine readings, equipment notes, and invoices then reads as one history instead of a folder of forwarded emails.