15.2 Basin, Deck, and Finish Maintenance

15.2 Basin, Deck, and Finish Maintenance

Quick Answer: Cementitious interiors etch when water is aggressive (negative Calcium Saturation Index) and scale when water is over-saturated (positive CSI)—test pH, total alkalinity, calcium hardness, and temperature (Chapter 5) before you scrape or add acid. Vinyl liners wrinkle and leak. Painted coatings peel from poor prep. Tile scum, grout, expansion joints, and coping are sanitation and fall surfaces. Decks injure people through trips, standing water, algae slime, failed caulk, and clogged drains. Depth markers and lane lines are finishes that are also safety equipment (Chapters 9 and 10). Calcium nodules and iron/copper stains are handled by testing water metals and using cautious sequential treatment. Acid washing is a trained procedure with PPE and AHJ limits, not a color-chart hobby copied from a copyrighted manual.

Basin and deck finishes are Domain 5 facility maintenance. They fail in public, they cut feet, and they advertise neglected chemistry. Independent OpenExamPrep teaching uses CSI logic from Chapter 5, ordinary commercial plaster and vinyl practice, and OSHA/AHJ caution for acid work. OpenExamPrep is not an NRPA finish-warranty program and does not reprint unpublished stain-identification trees.

Plaster and aggregate: etching versus scale

White plaster, quartz, pebble, and similar cementitious interiors are calcium-based. Water either dissolves them or plates extra mineral onto them.

Etching. When CSI stays negative long enough—often from low pH, low alkalinity, low calcium hardness, or cold water—the finish looks dull, sandy, or pitted. Grout recedes. Calcium hardness in the water may rise because the basin is donating mineral. The typical operator CSI window taught in Chapter 5 is about −0.3 to +0.3. A one-day dip is not a death sentence. A season of −0.8 while someone knocks pH down with acid every morning is how you eat an interior. First action is not a new plaster bid: retest pH, TA, CH, and temperature, stop unnecessary acid, and rebalance. Scraping to see if it is soft with a screwdriver creates the pit you will later blame on the water.

Worked example. Shallow-end plaster looks sandy. Today's tests: pH 7.1, TA 60 ppm, CH 120 ppm, cool water. You do not need a copyrighted factor table to recognize a negative-index climate. Common commercial targets sit near pH 7.2–7.8, TA often 80–120 ppm, and CH often 200–400 ppm, always subject to the AHJ. Raise the missing alkalinity and calcium per Chapter 3 dosage teaching, stop using acid as a daily cleaner, then recheck CSI. Ordering abrasive restoration while this water is still aggressive just donates the next interior.

Scale. A positive CSI, especially in hot spas with high pH, high TA, and high CH, deposits calcium carbonate on tile lines, ladders, and heater exchangers. The basin feels rough and looks white or tan. Scale in a heater is a mechanical failure (Chapter 8). Confirm CSI over several tests, correct the driving factors within AHJ limits, then plan physical or chemical removal. Do not acid-wash a spa every Friday because last August it scaled once.

A newly filled tank with very low CH can etch even if last week's spa was scaling. Test this water, not last month's story. Do not treat every rough spot as scale and every dull spot as etch without the four CSI factors in hand.

Vinyl liners

Vinyl is a membrane. CSI etching in the plaster sense does not apply the same way, but wrinkles, seam leaks, and wall-to-floor failures still close pools.

Wrinkles come from installation, thermal movement, groundwater pushing the liner, or a leak that lets the liner float. A wrinkle in a walking surface is a trip and cut hazard. Do not treat stretching it with the vacuum as a permanent repair. Restrict or close, find whether water is leaving the pool or entering from outside, and call a qualified liner technician.

Leaks show as water loss beyond evaporation (a bucket test is a teaching comparison, not a courtroom instrument), wet soil, or a hollow sound. Dye work around fittings belongs to trained leak detection. Operators first quantify the loss per day, check lights, returns, and skimmers, and stop silent topping-off without a work order in the maintenance file (Section 15.1). Water behind a liner hides algae and structure problems. Photograph the wrinkle or wet zone so the next shift does not reopen the shallow end out of habit.

Painted coatings

Epoxy and similar pool paints fail in sheets when prep was poor: old coating not removed, plaster not profiled, wet substrate, or paint over soap and algae. Chemistry can shorten life, but the classic failure is bond, not a single legal chlorine reading. Peel that makes a cut hazard comes off now. Recoating is a renovation decision (Chapter 13) with manufacturer instructions and often AHJ notice for a drained public pool. Painting over failure donates next season's flakes.

If bathers are in the water with peeling shards, treat the shards as a cut hazard: remove what you can reach, restrict the area, and do not sell the peeling as a cosmetic inconvenience.

Tile line, grout, expansion joints, and coping

Waterline scum is oil, lotion, and biofilm. Brush and use an AHJ-allowed cleaner. Habitual extra acid to eat the ring attacks grout and drives CSI negative.

Grout fails from aggressive water, freeze-thaw, and age. Missing grout is a cut pocket and a dirt trap. Put it on the PM list (Chapter 14); do not wait until a child slices a heel.

Expansion joints exist so concrete can move. Failed sealant lets water into the deck package, creating voids, trip lips, and freeze damage. Replace joint material as scheduled finish work, not as a rainy-day afterthought.

Coping is what people grab and sit on. A rocking stone is a close-the-zone defect, not a winter project you will get to. File photos and a work order the same day (Section 15.1).

Decks: where patrons actually get hurt

The deck injures more people than most plaster problems.

• Trip hazards: lips, broken tile, raised or missing drain grates, curled mats, hoses across walkways.
• Standing water: bad pitch, clogged deck drains, a hose left running. Standing water is a slip, ice in winter, and a map of settlement.
• Algae slime: shaded, north-facing, or constantly wet concrete grows a biofilm that behaves like ice. A wet-floor cone does not remove algae. Sanitize the deck, fix the water source, and keep the zone closed until it is not slippery.
• Caulk: failed coping-to-deck joints that let water under the slab.
• Deck drains: grate seated, not a toe-trap, channel clear. A missing grate fails the opening checklist (Chapters 10 and 12).

Photograph defects and open a work order. Chapter 9 identifies the hazard on the walk; this chapter maintains the surface so the same lip is not there tomorrow.

Depth markers and lane lines are finishes—and they are safety

Depth numerals, no-diving markings, and lane-line tiles or painted racing lines sit on the finish schedule. They are also safety information (Chapters 9 and 10). Faded numerals, markers that no longer match the water after a replaster, or peeling lane tiles that shard in the basin are not cosmetic.

Inspect markers on the opening walk. If a marker is unreadable, restrict diving or the area until it is restored. After a new interior, measure depths before you reopen; added plaster thickness can change the number you must show. Lane-line anchors and recessed tiles should not cut feet. Repair them as finish work and as a hazard control.

A cone that says deep water does not replace a required depth marker. Temporary signage is for the hour you are fixing the tile, not for the rest of the season.

Calcium nodules and metal staining—process, not a color tree

Calcium nodules feel like barnacles on plaster, often at pits or shell leaks. They are a finish clue and sometimes a leak clue. Log the location, check CSI and CH, and bring a plaster or leak professional if they spread. Do not chisel through the shell on a Saturday.

Iron staining often looks brown or rust-colored, especially with metallic fill water or a corroding steel component. Copper staining often looks blue-green, classically from aggressive water eating a copper heat exchanger or from copper-bearing algaecides. Those color hints are starting points only. Lighting, plaster tint, and mixed metals fool the eye. This guide will not dump an unpublished stain-identification tree from a copyrighted manual.

Operator process:

1. Test pool water and fill water for iron and copper, and retest CSI.
2. Find the source (fill, heater, fittings, algaecide) so you are not stain-treating forever.
3. Use sequential, labeled sequestering or stain products and filter aid per the SDS and label. Do not stack oxidizer, acid, and a metal product in the same hour because a forum said so. Incompatible additions are a chemical incident (Chapter 11).
4. Acid washing a basin is a trained job: ventilation, PPE the SDS names, neutralization, disposal, bather exclusion, and often AHJ notice. It can strip paste and ruin a finish if the water problem is not fixed first. It is not an entry-level weekend experiment.

Second worked example. Brown streaks appeared after a well-water fill. Test fill and pool for iron before anyone rents an acid-wash pump. If the fill is metallic, treat the source (sequester, pre-filter, different fill) or you will restain new white plaster. If CSI is also strongly negative, fix the water so you are not dissolving copper out of a heater at the same time.

Symptom, likely finish, and first operator action