Filling a Pool in Scottsdale: Your Tap Water’s Starting Numbers
Filling a pool in Scottsdale means starting from Scottsdale Water (City of Scottsdale)’s water — which is very hard at roughly 252 mg/L total hardness (about 14.8 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 Scottsdale Water (City of Scottsdale) numbers index at +0.57 — mildly scale-forming (how this is calculated). That puts Scottsdale 5th of the 15 cities here that publish enough to compute an index, counting from the most scale-forming down.
Read it as a ceiling rather than a verdict: utilities publish TOTAL hardness while the index wants the CALCIUM fraction, so the true figure sits at or below +0.57 — close enough to the balanced band that it should not alarm you. What it does settle is which mistake costs money in Scottsdale. Cloudy water and scale at the tile line are the failure mode here; etched plaster is not.
The top-off arithmetic
Evaporation removes pure water and leaves the minerals behind, so make-up water re-adds Scottsdale hardness every time. Replacing one full pool volume through top-off adds roughly another 252 ppm; starting from a fresh fill at about 252 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 6th 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. Scottsdale Water (City of Scottsdale) publishes a tight range — 215 to 290 mg/L, only 1.3x 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 Scottsdale water is like this
Supporting 2025 distribution data shows calcium 61.9-81.3 ppm, magnesium 27-42 ppm, alkalinity 113-135 ppm, sulfate up to 225 ppm, TDS 325-710 ppm, pH 6.7-8.2, sodium 48-140 ppm. Scottsdale states outright that it COULD implement additional treatment to address hardness but this would not be cost effective, especially since the majority of residential water consumption is outdoor use – so the minerals are a deliberate, disclosed policy choice, not an oversight.
The geographic split traces to infrastructure: north Scottsdale is fed from the CAP plant on Colorado River water, while SRP water reaching Chaparral is available only on ‘on-project’ lands, a historic entitlement footprint. That TDS range of 325-710 ppm is more than a 2x spread across one city – a Scottsdale pool owner who uses a citywide average for CH or TA calculations can be off by a wide margin.
No softening, by explicit and disclosed cost-benefit decision. Treatment is coagulation/flocculation, sedimentation, filtration and disinfection at the CAP Plant, with granular activated carbon to improve taste and odor and to treat disinfection byproducts. CAP III uses ultrafiltration membrane technology plus disinfection. The Chaparral WTP uses ultrafiltration membranes and granular activated carbon.
Scottsdale operates one of the most extensive aquifer recharge programs in the country, recharging highly treated recycled water and filtered CAP water at the Water Campus and through dual-use ASR wells – in winter, when demand is lower, some CAP-treated water is recharged rather than delivered, which is itself a seasonal driver of what reaches customers.
ZONAL: Scottsdale publishes an approximate-hardness-by-boundary table – South of Indian School Road 13-15 gpg (230-260 ppm), Indian School Road to Chaparral Road 13-17 gpg (215-285 ppm), North of Chaparral Road 13-17 gpg (230-290 ppm). Underlying this, SRP supplies are available only to certain parts of the city referred to as ‘on-project’ lands, unlike other supplies which can be used anywhere in the service area.
SEASONAL: the city states you may receive water from a single source or a combination depending on THE TIME OF YEAR, THE WEATHER AND CUSTOMER DEMAND. Its ASR operation reinforces this – in summer all CAP water treated at the CAP plant is used directly by customers, while in winter some is recharged through ASR wells instead.
Ongoing North System infrastructure work is explicitly aimed at increasing the city’s ability to move water from southern sources to northern Scottsdale, which would further shift blends by area over time.
Background sources: scottsdaleaz.gov, amwua.org, azmet.arizona.edu.
Before you drain or refill in Scottsdale
DRAINING: pool water should NEVER be discharged to the street – Scottsdale calls this not only a neighbor nuisance but ‘a violation of local, state and federal regulations,’ noting untreated pool water flows through the flood control system into retention basins or the Salt River where it can damage or kill aquatic life, and damages pavement.
Option 1 is irrigating your own landscape, with specific chemistry gates: WAIT THREE TO SEVEN DAYS after treatments before draining to let chlorine dissipate, and pH should be in the 7-8 range; for backwash used on landscaping, don’t add new chemicals for up to 72 hours, then use on salt-tolerant plants such as oleander, Bermuda grass and natal plum. To limit plant damage Scottsdale specifies testing for pH 6.5 to 8.5 and CHLORINE BELOW 0.1 mg/L. Water must be contained on your own yard.
Option 2 is the sanitary sewer clean-out: shut off power to the filtration system and TURN OFF THE AUTOMATIC WATER FILL VALVE if you have one, use a submersible pump, keep flow under 12 gallons per minute or the sewer may back up. Prohibited: draining into a sanitary sewer manhole in the street, into a storm sewer inlet or drainage channel, or onto adjacent property, drainage easements and watercourses. Scottsdale does not have records of clean-out locations; homes older than 20 years may not have one.
REFILL / BILLING: sewer use is not metered; sewer rates are updated annually in July based on your average water use in DECEMBER, JANUARY AND FEBRUARY. If refilling during those months you may request an adjustment by submitting a Sewer Charge Adjustment Request BY AUG. 31. POOL REMOVAL REBATE: Scottsdale was the first city in Arizona to offer a water conservation rebate to remove a pool or spa.
As of the current rebates page the residential removal rebates CLOSED March 31, 2026 and grass and pool removal rebates will return when the new rebate season launches; per ordinance all removal rebates require a PRE-INSPECTION BEFORE REMOVAL, and any in-ground pool already removed or in the process of being removed is NOT eligible.
Historically (AMWUA, 2016) the rebate was up to $1,500 at 50 cents per square foot of pool surface, with pre and post inspections, required landscaping of the vacated space, six months to complete after pre-inspection, and first-come-first-served funding; a Scottsdale permit and city inspection of the electrical disconnect were required, along with holes in the pool bottom to let rainwater drain. Current rebate terms are NOT confirmed for the next season.
Scottsdale also notes pool water drained to the city sewer is treated and recycled for future beneficial use.
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 Tucson — Same state, different water: Tucson fills at about 209 mg/L against 252 here.
- Filling a pool in Fort Worth — The other end of the scale: Fort Worth gets about 2.1 pool volumes of top-off against 0.6 pool volumes here.
Source: Scottsdale Water 2024 Water Quality Report (CCR); URL redirects to the report PDF (2024 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.