Filling a Pool in Corpus Christi: Your Tap Water’s Starting Numbers
Filling a pool in Corpus Christi means starting from Corpus Christi Water (CCW), PWS TX1780003’s water — which is hard at roughly 170 mg/L total hardness (about 9.9 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
At a typical 84 F pool temperature the published Corpus Christi Water (CCW), PWS TX1780003 numbers index at +0.18 — inside the balanced band (how this is calculated). That puts Corpus Christi 13th of the 15 cities here that publish enough to compute an index, counting from the most scale-forming down.
Since utilities publish TOTAL hardness and the index wants the CALCIUM fraction, +0.18 is a ceiling and the true figure sits at or below it — which for a near-balanced reading means Corpus Christi water can test slightly aggressive once it is in the pool. Worth knowing before you assume balanced water needs nothing.
The top-off arithmetic
Evaporation removes pure water and leaves the minerals behind, so make-up water re-adds Corpus Christi hardness every time. Replacing one full pool volume through top-off adds roughly another 170 ppm; starting from a fresh fill at about 170 mg/L, that reaches the 400 ppm ceiling after about 1.4 pool volumes of make-up water — a couple of pool volumes, which a high-evaporation summer gets through faster than most owners expect. That is the 16th 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
Less than you might think. Corpus Christi Water (CCW), PWS TX1780003 publishes a tight range — 158 to 236 mg/L, only 1.5x end to end — which is unusual on this list and genuinely useful: it means the figures above are stable enough to plan around rather than merely a system-wide average hiding a lot of variation.
Why Corpus Christi water is like this
THE KEY FACT: Corpus Christi’s numbers are high because its water is drought-concentrated surface water AND because the supply has quietly flipped its center of gravity.
CCW’s own 2025 report states the eastern supply (Colorado River via Lake Texana) ‘now accounts for approximately 70 percent of CCW’s water — a strategic diversification that has become critical as our western reservoirs face extended drought conditions.’ So the water most Corpus pool owners are filling with is majority lower-Colorado-River water that has traveled 101+ miles of pipeline, not Nueces basin water.
Published 2025 figures from CCW’s report: total hardness 236 ppm as CaCO3, total alkalinity 151 ppm, and TOTAL DISSOLVED SOLIDS 643 ppm — which is ABOVE the EPA secondary standard of 500 ppm, and CCW prints it as such. Supporting ions: chloride 178 ppm, sodium 121 ppm, sulfate 116 ppm, calcium 70.0 ppm, magnesium 14.8 ppm.
That TDS number is the single most important fact for a Corpus pool owner: fill water already starts at 643 ppm TDS, and because evaporation removes pure water and leaves every dissolved solid behind, a pool topped off all summer on this water climbs toward the 1,500-2,000+ ppm range where salt-cell and LSI calculations start misbehaving and where ‘drain and refill’ is the usual fix — except that draining is exactly what the drought ordinance restricts.
Note also the low calcium relative to the total hardness (70 ppm Ca vs 236 ppm total as CaCO3) means a large share of the hardness is magnesium and other ions that do NOT count toward the calcium hardness a pool test kit measures.
Background sources: corpuschristitx.gov, stage2.corpuschristitx.gov, gato-docs.its.txst.edu.
Before you drain or refill in Corpus Christi
In the Drought Contingency Plan definitions, ‘Non-essential water use’ expressly includes ‘Use of water to fill, refill, or add to any indoor or outdoor swimming pools or jacuzzi-type pools.’ The DCP also legally DEFINES a pool cover and closes an obvious loophole: ‘Pool cover: a material designated to cover the surface area of a swimming pool when it is not in use… Pool covers do not include tree canopies, pergolas, gazebos’ or similar structures.
STAGE TRIGGERS by combined Choke Canyon + Lake Corpus Christi storage: Water Shortage Watch below 50 percent (5 percent demand reduction target), Stage 1 Mild below 40 percent (5 percent), Stage 2 Moderate below 30 percent (10 percent), Stage 3 Critical below 20 percent (15 percent), then Water Emergency.
STAGE 2 (current): ‘A person or entity who owns, leases or manages an outdoor swimming pool (including City-owned pools) shall begin preparation for Stage 3 requirement to have approximately 100 percent of the pool surface area covered when not in use.’ The City’s own Stage 2 FAQ confirms: ‘Yes, filling, draining, and refilling existing pools is permitted at this time to maintain equipment operations.
Pools must have covers when not in use.’ STAGE 3: ‘The filling, draining and refilling of an existing swimming pool, Jacuzzi and hot tubs is prohibited except to maintain structural integrity.’ Plus ‘A person or entity who owns, leases, or manages an outdoor swimming pool (including City-owned pools) shall have approximately 100% of the pool surface area covered when not in use.
A request for an exemption or variance from this provision for pools that have a water-saving feature may be submitted.’ The codified ordinance version (Corpus Christi Code Ch. 55, Art. XII) reads: ‘The filling, refilling, or adding of water to swimming pools, wading pools, and jacuzzi-type pools, and hot tubs is prohibited except to maintain structural integrity.’ Water parks must get advance approval from the Chief Operating Officer of Corpus Christi Water before filling or adding water.
CURRENT STATUS: Stage 2 is in effect; combined reservoir capacity was 43.1 percent as of 08/13/26. Note the striking asymmetry a pool owner should understand: Corpus Christi went to Stage 3 on December 16, 2024 at 19.9 percent storage, and under Stage 3 ALL outdoor irrigation was banned — even hand-held hoses — while pool filling to maintain equipment was still allowed. Pools are treated as equipment to be protected, not as landscape. The 100 percent cover mandate is the price of that.
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 San Antonio — Same state, different water: San Antonio fills at about 300 mg/L against 170 here.
Source: CCW Monthly Mineral Analyses (Aug 2025 / Jan 2026 / May 2026 PDFs) + 2025 Water Quality Report (corpuschristitx.gov/media/gbwlvhok/corpus-christi-web-report.pdf) (2025-2026 report data), accessed 2026-08-11. 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.