📖 Deep dives

The Langelier Saturation Index predicts whether water will deposit scale or attack surfaces: LSI = pH + temperature factor + calcium factor + carbonate alkalinity factor − 12.1.

• Carbonate alkalinity is total alkalinity minus about one third of the stabilizer (CYA), so high CYA makes alkalinity look better than it is
• Warmer water and higher calcium push the index up, toward scale
• Aim for about −0.3 to +0.3. Below that, water is aggressive: etching, corroded heat exchangers, metal staining. Above it, water is scale-forming: cloudy water, scaled tile, fouled cells and heaters
• Salt and other dissolved solids change the constant, so use the right correction for salt pools
• Correct in order: alkalinity, then pH, then calcium. Heater and cell surfaces run hotter than the pool, so they scale first even when the pool reads near zero
• Document readings each visit so you can show a trend, not a snapshot

• Stabilizer protects chlorine from sunlight but also slows it. The higher the CYA, the more free chlorine you need to hold
• Many pros use a minimum free chlorine of roughly 7.5 percent of CYA on non-salt pools and keep a higher shock level for algae treatment
• Combined chlorine above about 0.5 ppm means chloramines. Break point shocking, roughly 10 times the combined chlorine, clears it
• Overnight chlorine loss test: after dosing, a loss of about 1 ppm or less overnight suggests little algae or organic demand
• Sunlight, heat, bather load, rain, and algae all raise demand
• Very high CYA calls for a partial drain and refill. There is no chemical fix
• Borates and good circulation reduce chlorine demand over time but do not replace sanitizer

Chlorine generators make chlorine and hydroxide, which is why pH rises and why scale forms on the cell plates.

• Scale: high pH or calcium, or a long run time. Reverse polarity cycles help but cannot overcome poor balance
• Low flow or running dry: gas builds up and damages plates and sensors
• Salt too low or too high: reduced output, errors, or overheating
• Oversized output for the pool, running the cell hard for no reason
• Age: plates wear with operating hours
• Power supply, board, and cable connection failures, often from moisture and corrosion
• Cold water: many cells reduce output or show false low salt
• Controller issues: Pentair's bulletin A00709 covers firmware 1.004 for IntelliChlor Plus and LT
• Always verify salt with an independent test before blaming the cell

• Causes of failure: voids in the setting bed, substrate movement, water behind the tile, freeze-thaw, scale lifting tile, failed expansion joints, and bond beam cracks
• Diagnose: lower the water, tap every tile on a grid, mark hollow spots on a photo, probe grout, check coping joints and the bond beam, and note moisture
• Spot repair when failures are isolated and the substrate is sound and dry
• Replace the band when hollow areas are widespread, repairs keep failing, tile cannot be matched, or coping work exposes the tile anyway
• Replacement outline: remove coping if needed, remove old tile and setting bed, repair the bond beam, set with a pool-rated adhesive, grout, and install a proper expansion joint
• Respect cure times before refilling to the waterline
• Document with photos and give the customer both options with costs

• Joint design matters: many sealant makers recommend depth about half the width within limits, so follow the product data sheet
• Backer rod sets the depth and a bond breaker keeps the sealant from sticking at the bottom, so it can stretch
• Adhesion failure means the sealant pulls off the edge, usually from poor prep, moisture, or the wrong product. Cohesion failure means the sealant tears in the middle, from movement or age
• UV, pool chemicals, heat, and joint movement shorten service life
• Replace by cutting out all old material, cleaning and drying, installing backer rod, priming if required, applying a pool-rated flexible sealant, and tooling it smooth
• Inspect yearly and re-seal before water gets under the deck or coping

• Water expands about 9 percent as it freezes. Saturated materials crack when it freezes, and each cycle widens the damage
• Entry points: failed mastic, cracked or loose tile, coping gaps, hairline cracks above the waterline, and poor deck drainage
• Progression: water in, freeze, crack widens, more water in, base washes out, deck settles
• Check winter water level for the cover type, skimmer and return protection, and plumbing blowout
• Drainage: slope the deck away, keep drains clear, and manage downspouts and irrigation
• Repair in dry weather, before the first freeze, and photograph findings for the customer

• Causes of finish failure: aggressive or scaling water, poor startup, hollow spots from bond failure, and leaks
• Patch small bond failures. Resurface when wear or delamination is widespread
• Hydrostatic pressure: high groundwater can lift an empty pool or crack the shell. Check the water table, avoid draining after heavy rain, and know where the hydrostatic relief valve is
• Resurface steps: drain, prepare the surface, bond coat, apply, fill quickly and evenly, and follow the finish manufacturer startup plan
• Brush and manage chemistry carefully during the first weeks

• Dry running: the shaft seal overheats and fails fast
• Air leaks and cavitation: erosion, noise, and lost prime
• Restricted flow: clogged baskets or impellers and undersized plumbing raise load and heat
• Heat: poor ventilation, direct sun, and tight enclosures shorten motor and drive life
• Moisture: bad seals and wet air lead to rusted bearings, capacitor failures, and drive faults
• Electrical: low voltage, loose connections, and failed capacitors
• Chemical fumes: storing chemicals near equipment corrodes motors
• Prevention: check water level, baskets, o-rings, flow, and amp draw each visit

• Low flow trips pressure switches and overheats the exchanger
• Scale from high pH, calcium, or alkalinity insulates the heat exchanger. Low pH corrodes it. Warranties often exclude chemistry damage
• Gas heaters: dirty flame sensors and burners, blocked vents or orifices, wrong gas pressure, and insects
• Condensation on cold startup can corrode exchangers that are not designed for it
• Short cycling from oversized units or bypass settings wears parts
• Heat pumps: dirty coils, blocked airflow, low flow, and refrigerant issues. Refrigerant work needs proper certification
• Keep chemistry logs and verify flow at every service

• Sand filters: cracked laterals or standpipes show up as sand in the pool. Multiport valve gaskets leak into the waste line
• Cartridge and DE filters: collapsed cartridges, torn grids, and cracked tanks or clamps
• Valves: worn diverters, failed o-rings, stuck or failed actuators
• Plumbing: poor prep or the wrong cement at glued joints, UV-damaged exposed PVC, freeze cracks, water hammer, and thermal expansion
• Restrictions: undersized lines, closed valves, and clogged returns raise pressure and reduce flow
• Settling and roots can break buried lines. Pressure test to find them

• GFCI trips: moisture in motors, lights, and junction boxes, damaged cords, and ground faults. Do not keep resetting
• Capacitors and contactors fail from heat and cycling
• Bonding: corroded or loose connections, and missing bonds after renovation work. Verify continuity per local code
• Surges and lightning damage boards, drives, and transformers
• Automation and communication faults: wiring polarity, shielding, loose terminals, and bad power supplies
• Enclosures: water, insects, and heat inside panels
• Safety: lock out power, test before touching, and use licensed electricians where required

Most equipment failures trace back to five root causes: flow problems, water chemistry, heat and ventilation, moisture, and installation errors.

• Gather facts: when it started, what changed, any codes or noises
• Check in order: power, flow and filter pressure, chemistry and temperature, controls and sensors, then components
• Measure instead of guessing: pressure, amp draw, voltage, temperature rise, and independent salt and chemistry tests
• Change one thing at a time and retest
• Photograph data plates, readings, and the failure
• Record the cause in the customer file, which also supports warranty claims