Filling a Pool in Jacksonville: Your Tap Water’s Starting Numbers
Filling a pool in Jacksonville means starting from JEA’s water — which is very hard at roughly 246 mg/L total hardness (about 14.4 grains per gallon). Here is what those published numbers actually do to a pool — and what they do not.
Which way this water pushes a pool
Reading scale-versus-etch direction needs hardness, alkalinity and pH together, and JEA does not publish alkalinity or pH. That direction cannot be computed from public data for this city and we are not going to guess it — a drop-count test kit reads all of it in about five minutes once the pool is full.
The top-off arithmetic
Evaporation removes pure water and leaves the minerals behind, so make-up water re-adds Jacksonville hardness every time. Replacing one full pool volume through top-off adds roughly another 246 ppm; starting from a fresh fill at about 246 mg/L, that reaches the 400 ppm ceiling after about 0.6 pool volumes of make-up water — less than one full pool volume — a hot-summer pool can work through that in a season or two, not decades. That is the 7th shortest budget of the 27 cities in this lookup.
Evaporation-only and deliberately the fastest case: splash-out, backwash and rain all dilute, and this uses published total hardness rather than the calcium fraction a kit reads (how this is calculated).
How much your own tap may differ
JEA reports hardness spanning 120 to 372 mg/L — a 3.1x range end to end. That is not measurement noise. It is what blending different sources into different service zones does over a year, and it means the single number at the top of this page is an average your own tap may not match. A pool a few neighbourhoods away can legitimately fill at a different hardness than yours. Test what comes out of your hose; do not plan off the midpoint.
Why Jacksonville water is like this
Jacksonville fill water is essentially raw Floridan aquifer carbonate chemistry delivered with almost nothing done to its mineral content. The aquifer sits in limestone, and water moving through it dissolves calcium carbonate, which is the entire source of the hardness and the carbonate alkalinity.
JEA does NOT soften: the treatment train is aeration (to strip hydrogen sulfide, the ‘rotten egg’ sulfur odor characteristic of deep Floridan water) followed by chlorine disinfection, with ozone used at two plants for sulfide removal and taste/odor. Nothing in that train adds or removes calcium.
So a pool owner topping off in Jacksonville is adding water whose hardness AND alkalinity both came from dissolved limestone – which is why total alkalinity tends to ride high alongside hardness and why pH drifts upward and scale forms on heaters and tile rather than the water turning aggressive.
The other consequence of the treatment choice: JEA’s per-JEA-page distribution disinfectant is chlorine (free chlorine), not chloramine, so fill water behaves predictably on a standard free-chlorine test – unlike the chloraminated Tampa Bay systems to the south. NOTE: a commonly repeated figure of 12-15 grains per gallon for Jacksonville appeared in search summaries alongside water-treatment vendor pages; I did not verify that number on a JEA page I opened and do not assert it.
Aeration for hydrogen sulfide removal, then chlorine disinfection per health regulations. Ozone is additionally used at two plants for sulfide removal and taste/odor improvement. No lime softening, no blending with surface water, no chloramination noted on JEA’s own water supply page.
Strongly zonal, and JEA documents it. The 2025 Water Quality Report reports results SEPARATELY for five grids (Major, Mayport, Lofton Oaks, Ponte Vedra, Ponce de Leon), and the values differ materially between them – for example the Major Grid reported chloride reaching 319 ppm (above the 250 ppm secondary standard) while Mayport showed no such result, and threshold odor numbers ran 44.7 (Major), 56.6 (Lofton Oaks) and 10 (Mayport).
‘Jacksonville tap water’ is therefore not one water; which grid serves an address changes what comes out of the hose. Seasonal variation is inherently small because the source is a deep confined aquifer rather than a river.
Background sources: jea.com, aws.sjrwmd.com, sjrwmd.com, floridadep.gov.
Before you drain or refill in Jacksonville
THREE distinct rules, all pool-specific.
- SEWER CREDIT – JEA runs a dedicated ‘Pool Fill Affidavit.’ It adjusts SEWER charges only (‘JEA will only adjust sewer charges for pool fill requests. Customers who do not have sewer services with JEA, will not receive an adjustment’). Eligibility: an active JEA account with sewer service, and either a new pool fill (requires a current permit from the Building Inspection Division) or a refill made necessary by pool structure/equipment repairs (requires the contractor’s state certification/registration number). Must be submitted within 30 days of completion. Limit ONE adjustment per 12 months. Processing takes up to two billing cycles; JEA determines the amount from meter readings. Routine seasonal refills do not qualify – only new construction or repair.
- DROUGHT – Duval County is inside the SJRWMD Phase III Extreme Water Shortage Order (F.O.R. No. 2026-0005, executed May 11, 2026, covering Alachua, Baker, Bradford, Clay, Duval, Flagler, Lake, Marion, Nassau, Putnam and St. Johns counties). Under section 9.d ‘Water-Based Recreation’ the order states verbatim: ‘All pools shall be maintained in a manner that minimizes the need for make-up water, such as promptly repairing leaks.’ Section 9.e states ‘Aesthetic uses of water are prohibited.’ Landscape irrigation is cut to one day per week and prohibited 8:00 a.m. to 6:00 p.m. (odd addresses Saturday, even Sunday, non-residential Tuesday). CRITICAL READING: the order does NOT ban filling or topping off a residential pool – it imposes an affirmative duty to minimize make-up water and fix leaks promptly. JEA has applied the once-a-week irrigation schedule to potable, reclaimed and reuse customers alike.
- DRAINING – Florida DEP guidance cites Subsection 62-302.530(19), F.A.C., limiting chlorine discharged to surface water bodies to <=0.01 mg/L, and Florida DOH Subsection 64E-9.007
- ‘Pool waste water disposal’: ‘Pool waste water shall be discharged through an air gap; disposal shall be to sanitary sewers, storm sewers, drainfields, or by other means, in accordance with local municipal and building official requirements including obtaining all necessary permits.’ Jacksonville’s Chapter 754 Stormwater Management Utility Code reportedly lists ‘dechlorinated swimming pool discharges’ among the discharges excluded from the definition of ‘illicit discharge’ – REPORTED ONLY: the Municode node returned a JavaScript shell with no readable text when I fetched it, and the coj.net page is a landing page linking out, so I did not render that ordinance text myself.
Rules change and enforcement varies — confirm with your water provider before draining or refilling. Nothing here is legal advice.
Worth a look next door
- Filling a pool in Orlando — Same state, different water: Orlando fills at about 129 mg/L against 246 here.
- Filling a pool in Fresno — The other end of the scale: Fresno gets about 2.1 pool volumes of top-off against 0.6 pool volumes here.
Source: JEA Water Hardness Levels (by zip code) + JEA 2025 Water Quality Report (jea.com/WQR2025) (2024-2025 report data), accessed 2026-08-10. Values are the utility’s published system-wide figures; your tap can vary by service zone and season.
Data page generated 2026-08-15. Part of the pool fill-water lookup.