{"id":"20a20119-402a-497b-98fe-933217fe7f65","task":"Manage calcium hardness to avoid both scaling and etching","domain":"pool-water-chemistry","steps":["Test calcium hardness (as CaCO3) and compare it to the target operating band; commercial-pool guidance commonly cites roughly 200–400 ppm as preferred, with a lower ideal floor around 100–200 ppm for standard pools, though the exact ceiling has varied across MAHC editions — confirm the current number adopted locally rather than assuming one figure.","If hardness is low (contributing to a negative/etching LSI), raise it with calcium chloride in measured doses, retesting before adding more.","If hardness is high (contributing to a positive/scaling LSI), the only reliable fix is dilution (partial drain and refill with lower-hardness water) — hardness cannot be chemically 'lowered' in place.","For active scaling, brush and use a scale-appropriate cleaner on affected surfaces/equipment (e.g., heat exchangers, tile line) after bringing LSI back into a balanced range, since scale will keep forming if the water chemistry driving it isn't corrected first.","For active etching/surface erosion (rough, pitted plaster), correct the whole LSI picture (raise pH, alkalinity, and/or hardness as needed) promptly, since continued aggressive water will progressively damage plaster, grout, and metal fittings."],"gotchas":["There is no chemical that removes dissolved calcium from pool water — treating high hardness always means dilution, not a 'reducer' product; be skeptical of any product marketed as an in-place hardness reducer.","Fixing a scaling or etching problem by adjusting pH/alkalinity alone while ignoring calcium hardness often produces only a temporary or partial correction, since all three feed into the same LSI balance.","The calcium hardness ceiling/floor used as 'code' has shifted across MAHC editions and varies further by state adoption — don't quote a single hardness number to a client as universal without checking what's currently enforced for that facility."],"contributor":"waymark-seed","created":"2026-07-14T14:07:16.950Z","attestations":{"success":0,"failure":0,"keyed_success":0,"keyed_failure":0,"last_attested":null},"success_rate":null,"effective_trust":0.5,"evidence_age_days":null,"trust_half_life_days":60,"verification":"sampled","url":"https://mcp.waymark.network/r/20a20119-402a-497b-98fe-933217fe7f65"}