Pool Losing Water: Is It Evaporation or a Leak?

You're topping off your pool more often than usual. Is it the Arizona sun — or is something leaking underground? This is one of the most common questions we get from pool owners across Phoenix, Tucson, and Southern Arizona. Here's how to answer it yourself before calling a professional.

How Much Evaporation Is Normal in Arizona?

In the Phoenix and Tucson areas, a typical residential pool loses about 1/8 to 1/4 inch of water per day to evaporation during the summer months (May–September). In the peak of July and August, when temperatures hit 110°F+ and humidity is in the single digits, it can push toward 1/2 inch per day for larger pools.

In winter (November–February), evaporation drops to 1/16 to 1/8 inch per day. If you're losing more than this, you likely have a leak.

The Bucket Test: How to Tell Evaporation from a Leak

This is the gold-standard DIY test. You need: a 5-gallon bucket, a marker, and a brick or weight.

1. Place the bucket on a pool step (or use the weight to submerge it so it's stable) with the rim of the bucket above the water line.
2. Fill the bucket with pool water until the water level inside the bucket matches the water level of the pool outside the bucket.
3. Mark both water levels — the one inside the bucket and the one on the outside of the bucket or pool tile.
4. Wait 24 hours. Do not run the pump, use the pool, or add water during this period.
5. Compare the levels. If both dropped by the same amount, it's evaporation. If the pool level dropped more than the bucket level, you have a leak — the pool is losing water through something other than evaporation.

Other Signs Your Pool Has a Leak (Not Evaporation)

• Wet spots in the yard near the pool or equipment pad — especially if they never dry out
• Air in the pump basket or bubbles coming from the return jets (indicates a suction-side leak)
• Cracks in the pool shell, tile, or deck that are new or widening
• The auto-fill runs constantly — turn it off for a day and measure the drop
• Chemical levels are unstable — you're constantly adding chemicals because fresh (unbalanced) water keeps entering the system
• Water loss continues in winter when evaporation is minimal

Common Pool Leak Locations

If the bucket test says "leak," here's where they're usually hiding:

• Skimmer throat — where the skimmer meets the pool shell, sealant can crack
• Return fittings — the jets that push water back into the pool
• Light niche conduits — the housing for underwater lights is a very common leak point
• Main drain line — especially in older pools with original plumbing
• Underground plumbing — suction and return lines running between the pool and the equipment pad
• Shell cracks — structural cracks in the pool wall or floor from ground movement

When to Call for Professional Pool Leak Detection

If the bucket test confirms a leak, or if you're losing more than 1/2 inch per day even after ruling out evaporation, it's time to call. Our pool and spa leak detection service uses pressure testing, acoustic equipment, and dye testing to isolate the leak — whether it's in the shell, the plumbing, or the equipment. We find it, mark it, and hand you a report so your pool contractor knows exactly where to repair.

We serve pool owners across Phoenix, Scottsdale, Gilbert, Tucson, and all of Southern Arizona.