When and How to Drain Your Pool in Phoenix

Draining and refilling your pool is one of the most important maintenance tasks in Arizona — but it’s also one of the most misunderstood. Here’s what every Phoenix pool owner should know.

Why Pools Need to Be Drained

Over time, pool water accumulates dissolved minerals, chemicals, and contaminants that can’t be filtered out. This is measured as Total Dissolved Solids (TDS).

As water evaporates and is replaced (either by autofill or manual filling), the TDS concentration increases. Fresh water coming in has a TDS of around 500–800 ppm in the Phoenix area. But the minerals that were in the evaporated water stay behind, concentrating over time.

When to Drain

The general rule: drain your pool every 3–5 years, or when:

TDS exceeds 3,000 ppm — Chemistry becomes difficult to manage and water looks dull
CYA (stabilizer) exceeds 100 ppm — Chlorine becomes ineffective regardless of how much you add
Calcium hardness is very high — Scaling on surfaces and equipment
Water clarity won’t improve — Despite proper chemistry and filtration

Best Time of Year to Drain in Phoenix

October through April is the only safe window. Here’s why:

Pool plaster and pebble surfaces can be damaged by extreme heat and direct sun when the pool is empty
A drained pool during summer can crack, delaminate, or even “pop” out of the ground from hydrostatic pressure
Monsoon rains can flood an empty pool with muddy water

The sweet spot is usually late October through March when temperatures are consistently below 90°F.

City Drain Permits

Most Phoenix-area cities require a drain waiver or permit before you can discharge pool water to the storm drain or sanitary sewer. This includes:

City of Phoenix
City of Scottsdale
City of Mesa
City of Tempe

Fines for draining without a permit can be significant. The waiver process is typically straightforward — it’s a form submission, not a lengthy approval. Professional pool service companies handle this as part of the drain and refill service.

The Drain Process

A professional drain and refill typically goes like this:

Permit/waiver filed with your city
Pool drained using a submersible pump (not the pool pump)
Surfaces cleaned while the pool is empty — acid wash or chlorine wash if needed
Quick turnaround — the pool should never sit empty longer than necessary
Fresh water fill — usually takes 12–24 hours depending on pool size and water pressure
Chemical startup — pH, alkalinity, chlorine, CYA, and calcium balanced from scratch

The TDS Reset

After a drain and refill, your TDS drops from potentially 3,000+ ppm back to the baseline of your city water (500–800 ppm in Phoenix). This gives you years of chemical headroom and makes water balancing dramatically easier.

You’ll likely notice the difference immediately — the water looks and feels different. Clearer, smoother, and more responsive to chemical treatment.

Cost Considerations

The cost of a drain and refill includes the service itself plus the water to refill. A typical residential pool holds 15,000–25,000 gallons. At Phoenix water rates, the water alone costs roughly $60–120. The service cost varies by company and whether surface cleaning is included.

Need a drain and refill in the Phoenix area? Contact Splash Mob Pools — we handle permits, draining, cleaning, and chemical startup.