How often should I drain my pool in Arizona? It is one of the most common questions Valley pool owners ask, and the honest answer is: less often than you might think, and only when the water tells you. A desert pool loses water to the sky every day and keeps everything that was dissolved in it. Over a few summers that build-up makes the water hard to balance, and that, not a date on the calendar, is what decides when fresh water makes sense.
Phoenix Pool Cleaning Pro is a free phone line, not a pool company. If you want someone to test your water and tell you whether a drain is due, call (623) 240-0428 any hour and you will be put through to an independent local pool service company that does the testing, quotes and does the work itself.
How often should I drain my pool in Arizona? What the sources say
No agency sets a draining schedule for backyard pools, and the official guidance leans toward draining rarely. The Arizona Department of Water Resources (ADWR) says swimming pools seldom need draining. Glendale's pool draining guidance asks residents to limit draining and refilling and to drain only when water quality requires it.
The clearest test comes from the pool industry. The Pool and Hot Tub Alliance (PHTA), the pool and spa industry's trade association, recommends that total dissolved solids, or TDS, stay no more than 1,500 parts per million above the level measured when the pool was first filled. TDS is simply everything dissolved in the water: calcium, salts, stabilizer, and leftovers from every chemical ever added. PHTA says going past that line may mean the water needs a partial or complete drain, as long as drought rules or other limits on draining are not in effect.
Salt pools work on a different baseline. A salt chlorine generator needs salt in the water, so a salt pool's TDS starts high. PHTA counts the salt added at startup as part of the starting TDS, so the 1,500 ppm allowance is measured from that higher number.
The practical answer. Have calcium hardness, stabilizer (cyanuric acid) and TDS tested a few times a year, and write the numbers down. When they climb past what the pool company can balance with chemicals, plan a partial drain. How long that takes depends on your fill water, how much evaporates and how much chemical goes in, which is why testing beats the calendar.
Why Arizona pool water wears out
ADWR says a standard uncovered pool in Arizona loses four to six feet of water a year to evaporation, most of it in summer. When water evaporates, the minerals in it stay in the pool. The top off water then brings in more. ADWR adds that, counting refills and backwashing, an uncovered pool uses roughly its own volume of water each year, and that draining the pool doubles that amount.
The fill water starts hard. The City of Phoenix's annual water quality report shows hard tap water that already carries a good load of dissolved minerals, so a pool's TDS starts well above zero before a single inch evaporates.
Three things build up as a result. Calcium hardness climbs, and in hot water calcium comes out as white scale on tile, in heaters and on salt cell plates. Cyanuric acid, the stabilizer that shields chlorine from ultraviolet light, builds up from stabilized chlorine tablets and only leaves when water leaves. And general TDS rises with every bag of salt, every dose of chlorine and every inch of top off water. A careful pool technician uses the Langelier Saturation Index (LSI), a calculation that combines pH, alkalinity, calcium and temperature, to judge whether the water will deposit scale or eat at plaster. When the numbers make that balance impossible to hold, dilution is the fix.
Signs it may be time for fresh water
None of these alone proves a drain is needed. Each one is a reason to have the water tested properly and the numbers compared with your fill water.
| What you notice | What it can mean | What to have tested |
|---|---|---|
| White crust returns on the tile soon after a tile cleaning | Calcium hardness is so high the water keeps dropping scale | Calcium hardness, pH, alkalinity, the LSI at summer water temperature |
| Chlorine reads fine but the water clouds or grows algae anyway | Stabilizer may be high enough to slow chlorine down | Cyanuric acid and free chlorine together |
| Chemicals seem to stop working or the water tastes salty | Total dissolved solids may be far above the fill level | TDS, compared with a tap water sample (and the salt level on a salt pool) |
| Scale on the salt cell or heater, or a filter that clogs with fine crust | Mineral build-up in equipment | Calcium hardness and LSI; have the equipment looked at |
| Years of topping off with no water replaced | Everything dissolved has been concentrating the whole time | A full panel: calcium, stabilizer and TDS |
A home test kit is fine for chlorine and pH. Calcium, stabilizer and TDS are worth having tested by a pool company, since the decision to drain rests on them. The pool tile cleaning page explains what happens to scale that has already formed, and weekly pool cleaning and maintenance covers the routine testing that spots the trend early.
Partial drain or full drain?
Most of the time the goal is to lower the numbers, not to see the bottom. How far to go depends on how high the readings are and whether any work needs the pool empty.
Partial drain and refill
The water is lowered part of the way and topped back up with fresh tap water, which dilutes calcium, stabilizer and TDS by roughly the share replaced. The finish stays mostly underwater, less water is used, and the pool is back in service sooner. If one round is not enough, a second can follow once the water is retested.
Full drain
An empty pool is needed for resurfacing, many structural repairs and some acid work, which is a job for a professional. It also carries more risk. The National Plasterers Council warns that where groundwater is high, an empty pool can be pushed up out of the ground, and advises confirming a hydrostatic relief valve is in place before draining.
Why the season matters
The National Plasterers Council lists failing to keep a plaster finish underwater among the causes of the finish coming loose, and notes that newer plaster still curing is more easily harmed when the pool is drained. National Weather Service normals for Phoenix show average highs above 100 degrees from June through August. Ask the company how it will protect an exposed finish in that sun, and whether a cooler month would suit.
Drain only when the water calls for it
Glendale asks residents to limit how often they drain and refill and to drain only when water quality requires it, and ADWR notes that draining doubles the water a pool uses in a year. If the numbers can be brought down another way, such as a smaller partial drain or reverse osmosis, ask about it first.
Where drained and backwashed pool water may go, city by city
Valley cities work to keep treated pool water out of the storm drain system, because storm drains carry water untreated to washes, retention basins, parks and lakes. Pool water carries chlorine, salt and dirt. The details differ, though, and they apply to filter backwash as well as a full drain. These are the rules each city publishes; check the linked page for yours before any water leaves the yard.
| City | Allowed | Not allowed, and other limits |
|---|---|---|
| Phoenix | The sanitary sewer cleanout on your property, recommended at no more than 12 gallons per minute, or watering your own landscaping. | No storm drain (City Code Chapter 32C), street, alley or right of way. Homes with no cleanout may discharge dechlorinated water to the right of way only by permit, under 50 gallons per minute and under 1 part per million chlorine; backwash and saltwater are excluded. |
| Scottsdale | Your own landscape, drained slowly over a few days so the water soaks in and stays on your property, or the sewer cleanout. Go slowly: the city's pool code page says under 12 gallons per minute, and its water quality page gives 50 as the most. | Not to the street, a storm drain or a neighbor's property. If a blockage on private property causes a sewer overflow, the owner pays for the cleanup. |
| Mesa | The sanitary sewer cleanout on your property, with no notification or permit, once the water is near neutral pH (6 to 8); the city suggests waiting 3 to 7 days after treatments so chlorine can dissipate. Cartridge rinse water goes over gravel, lawn or planted areas. | Never toward a sewer manhole in the street, and no soil, sand or debris down the cleanout. Acid wash and other repair wastewater may go to neither the storm sewer nor the sanitary sewer. |
| Chandler | Keep the water on your own property, or send it to the sewer cleanout on your property; no permit needed. No more than 12 gallons per minute is recommended. | A pipe that discharges to the street, an alley or other right of way counts as a direct connection to the storm drain system and is prohibited. Do not make the drain line to the cleanout a permanent fixture. |
| Gilbert | Your yard, if it can absorb the water without runoff; the sewer cleanout when there is no room, and for salt pools or water high in chemicals. The curb and gutter only for clean, dechlorinated water. No permit required. | No runoff into a ditch, street, storm drain or retention area, and no flooding a neighbor. The yard method is not for lake communities or streets with flooding problems. Follow your HOA policy too. |
| Tempe | Check the city's pool draining page before you start. Tempe's water efficiency guidance suggests reusing backwash water on salt-tolerant landscape plants. | Keep pool water out of streets and storm drains, which Tempe notes carry runoff untreated to parks, retention basins, washes, canals and lakes. |
| Glendale | The home's sewer cleanout for large amounts, at no more than 12 gallons per minute; backwash may irrigate landscaping. | No pool or spa water into any public street, alley or right of way. Avoid salt-sensitive plants such as citrus and hibiscus. |
| Peoria | Peoria publishes its own guide to draining and backwashing safely and legally; read it before any water leaves the yard. | See the city guide for its limits. |
| Surprise | Let it soak into your own yard without runoff, or send it to the sewer cleanout on your property at no more than 12 gallons per minute. Backwash can water salt-tolerant plants. | Nothing off the lot: not the street, curb, sidewalk, a retention basin or a neighbor's yard, and that includes backwash. Never into a septic system. |
| Apache Junction | The city's stormwater program allows backwash or drain water into the storm drain system only when no chemicals, chlorine included, were added for at least three days before. | Other discharges are treated as possible illicit discharges, with civil fines of up to $2,500. |
Using a sewer cleanout safely
A cleanout is usually a capped pipe near the house, often in the front yard; Surprise describes a rubber or threaded cap with a square wrench fitting. Phoenix warns that most pool filter pumps push water out too fast for a home sewer line, which can back water up into the yard or the house, and Glendale suggests a small submersible pump instead. Check showers and tubs right after the water starts flowing, and stop at once if anything backs up. Scottsdale notes that homes older than about 20 years may not have a cleanout at all. In Gilbert, water that runs into a neighbor's yard is treated as a civil matter between the property owners.
Reverse osmosis: cleaning the water instead of dumping it
There is a middle path between living with hard water and draining it. Mobile pool water recycling uses reverse osmosis, the same process as an under-sink drinking water filter, on a much larger scale. A trailer-mounted unit is parked near the pool, hoses draw water from the deep end, the water is pushed through fine membranes that hold back dissolved minerals, and the cleaner water flows back into the pool. Pool and Spa News has covered these mobile units as a way to lower cyanuric acid, total dissolved solids and calcium while the pool stays full.
Two cautions. First, the process is not waterless: some water is lost along the way, so ask how much and where that water goes, because your city's discharge rules still apply to it. Second, ask what the treated water will test at for calcium and TDS, so you can compare that with a partial drain.
Arizona's water picture and your pool
Much of the Valley's water comes from the Colorado River through the Central Arizona Project (CAP). The CAP reports that the river is in a Tier 1 shortage for 2026, which cuts Arizona's Colorado River supply by 512,000 acre-feet, about 30 percent of CAP's normal supply. Every full drain and refill uses a pool's worth of treated drinking water, and ADWR's model water waste ordinance lists the periodic draining of pools among the uses communities may choose to regulate.
The biggest lever is evaporation. ADWR says a pool cover can save 90 to 95 percent of the water a pool loses to evaporation. Less evaporation means fewer top offs, which means fewer new minerals and a longer stretch before the water needs replacing. Using a cartridge filter, or backwashing only when the pressure gauge calls for it, saves water too. The guide to how often to clean a pool filter covers the pressure rule. One more benefit of the sewer route: Mesa notes that pool water sent to the sanitary sewer can be treated and reused for landscape irrigation or groundwater recharge.
Safety during a drain
- Children. A partly empty pool is still a drowning risk, and an empty one is a fall risk. Keep gates latched and never leave a child alone near the pool.
- Chemicals. Never mix pool chemicals with each other. Store them apart, dry, shaded and out of children's reach, follow the label, and leave acid work to a professional.
- Equipment. Do not run the pool pump dry. Ask the company how it will handle the equipment while the water is low.
- Electricity. Keep cords and submersible pumps out of the way of standing water, and if a breaker or GFCI trips more than once, leave it off and call a professional.
- Neighbors. Watch the hose and the yard so water does not run onto the next lot or into the street.
Questions to ask before a pool company drains your pool
- What do calcium, stabilizer and TDS test at now, compared with my tap water?
- Would a partial drain do it, and how much water would you replace?
- Where will the water go, and does that match my city's rules?
- Does my pool have a hydrostatic relief valve, and how will you protect the finish if it is exposed?
- Would reverse osmosis treatment be a better fit, and how much water would that use?
- If resurfacing or repair is part of the job, what is your ROC license number?
Check the license first. Arizona's Registrar of Contractors (ROC) licenses contractors, and its residential classifications include R-6, Swimming Pool Service and Repair. Repairs, equipment replacement and resurfacing generally call for a licensed contractor; whether a cleaning-only service needs a license is not spelled out, so ask the ROC if it matters to you. Ask the company for its ROC license number and look it up on the ROC contractor search (opens in a new tab) before work begins. The line does not check this for you.
Not sure if your pool water is worn out? Call any hour, describe what you are seeing, and you will be put through to a local pool company that can test it.
- Call the numberAn automated assistant answers (623) 240-0428 day or night, weekends included.
- Describe the poolSay what is going on: cloudy or green water, a pump that hums, a heater that will not fire, scale on the tile, and which part of the Valley you are in.
- Get put throughThe call is transferred to an independent, locally owned pool service company, which hears a short summary of the problem before it picks up.
- Deal with them directlyThat company looks at the pool, quotes, does the work and bills you. If it cannot answer, your name, number, area and problem are passed along so it can call you back.
About this line: Phoenix Pool Cleaning Pro is a free phone line, not a pool company. It answers your call and connects you with an independent local pool service company, which inspects, quotes and does the work, and which you pay directly. Companies may pay a referral fee. You never pay the line. See how the line works.