Pool Leak Detection & Repair in Altadena, CA
Sonar, dye testing, and pressure testing for residential pool and spa leaks across the SGV. Drought-aware service with no unnecessary draining.
A pool leak is any unintended water loss from a swimming pool or spa system. The water can be escaping through a crack in the shell, a failed fitting at a skimmer or return line, a deteriorated seal at a light niche, or a leak in the underground plumbing that connects the pool to its equipment pad. Southern California has more residential pools per capita than almost any region in the country, and Altadena, Pasadena, San Marino, and Arcadia together hold thousands of them. With ongoing drought conservation requirements across LA County, an undetected pool leak now costs both money and water-rights goodwill at the same time.
How to tell a pool leak from normal evaporation
SoCal pools lose water to evaporation every day, and the rate varies by season, wind, and surface area. In summer, a typical residential pool in Altadena or Pasadena loses about a quarter inch per day. Winter rates are lower. Splash-out from swimmers and backwashing the filter also remove water without being a leak. So the first job in any suspected leak case is separating real leak loss from normal water loss.
The bucket test is the standard homeowner check. Fill a bucket with pool water, set it on a step submerged to match the pool's water level, mark both levels with tape, and check 24 hours later. If the pool has dropped more than the bucket, you have a leak. If they match, you're seeing evaporation. We run the same test as part of our diagnostic when leak presence isn't already confirmed.
Sustained water loss of half an inch or more per day, after evaporation is ruled out, almost always means a leak. At that rate a typical residential pool can lose 800 to 1,500 gallons a week.
How we find pool leaks without draining
Pool leak detection has moved beyond the era of guessing where the leak might be and excavating to find out. We use a combination of methods to locate leaks while the pool stays full, which preserves both the pool's chemistry and the water itself.
Sonar leak detection
Underwater listening equipment picks up the sound of pressurized water escaping from a fitting, line, or shell crack. A trained technician can isolate the leak source to within a few inches. Sonar works on full pools and is the primary method for first-pass leak location.
Dye testing
Once sonar has narrowed the search area, dye testing confirms specific leak points. A small amount of colored dye released near a suspect fitting, light niche, or shell crack will be drawn into the leak if one exists. Dye is non-toxic and dissipates quickly. The visible flow into a crack or fitting is unmistakable.
Pressure testing of plumbing lines
For underground line leaks, we isolate each plumbing run (return, suction, main drain) using plugs and a pressure pump. A line that loses pressure over a timed interval has a leak somewhere along its length. We then trace the leak point with acoustic equipment to plan the most targeted repair.
Helium leak detection
For especially small or hard-to-locate leaks in pressurized pool lines, helium tracer gas can be introduced into the line and detected at the leak point using a specialized sniffer. This method is used when sonar and pressure testing don't fully isolate the leak.
Repair methods we use after a pool leak is located
Once the leak is pinpointed, the repair approach depends on where the leak is and what it's leaking through.
Skimmer reseal or replacement. Skimmers separate from the pool shell over time as the bond breaks down. We reseal the skimmer-to-shell joint with pool-grade epoxy or, when separation is severe, replace the skimmer body entirely.
Return line and suction line repair. Underground plumbing leaks can sometimes be repaired by exposing the leak point and replacing the affected section. For multiple-leak older systems, rerouting the line above grade or relocating it through accessible decking is often the better long-term move.
Shell crack repair. Plaster, pebble, and fiberglass pool shells crack differently. Plaster cracks can often be ground out and patched with matching material. Fiberglass cracks need resin and reinforcement. Vinyl liner pools may need a patch or full liner replacement depending on tear size.
Light niche repair. Pool light niches often develop leaks at the conduit penetration. We can reseal the niche in place or, for severe leakage, replace the niche assembly.
Spa and hot tub leaks. Spas have similar leak modes (fittings, lines, shell, jets) but compressed into a smaller footprint. Spa leak detection often runs faster than full pool detection.
Cost of pool leak detection and repair in the SGV
Typical price ranges (Altadena / SGV market, 2026)
Detection only: $300 - $650 depending on pool size and methods used.
Simple repair (skimmer reseal, fitting replacement): $250 - $800.
Underground line repair: $800 - $2,500 depending on access and length.
Light niche reseal: $400 - $1,200.
Shell crack repair: $500 - $3,000+ depending on size, surface type, and whether color matching is required.
Full line reroute (return or suction): $2,500 - $6,000 depending on length and access.
San Marino and La Cañada Flintridge tend toward the higher end of these ranges, where larger pools and longer plumbing runs are common. Detection itself is roughly consistent across the SGV. We give a firm price for repair after detection is complete and we know what we're actually fixing.
Other pool plumbing work we handle
Beyond leak detection and repair, we work on pool equipment plumbing at the equipment pad, including pump and filter plumbing replacement, multiport valve repair, heater connection plumbing, and gas line work for pool heaters when natural gas service needs upgrade or relocation. We also test and replace residential irrigation backflow assemblies under California's Title 17 program when the irrigation system and pool fill line share a connection point. For pool fill compliance and conservation guidance, the California Department of Water Resources publishes regional drought-era requirements.
Frequently asked questions
How do I know if my pool is leaking or just evaporating?
The bucket test is the standard first check. Fill a bucket with pool water, set it on a step submerged to match the pool's water level, mark both levels, and check after 24 hours. If the pool drops more than the bucket, you likely have a leak. Normal SoCal evaporation runs 1/4 inch a day in summer, less in winter. Sustained loss above that is a leak indicator.
Do you have to drain my pool to find the leak?
In most cases, no. Sonar leak detection and pressure testing work on a full pool. We only drain pools when a specific repair requires it, such as a structural shell crack repair on a plaster or pebble surface. Drought conservation in LA County makes drain-free detection even more important.
What is sonar pool leak detection?
Sonar leak detection uses underwater listening equipment to pick up the sound of water escaping under pressure from plumbing lines, light fittings, return jets, and the shell itself. The technique can pinpoint a leak source within a few inches without draining or excavating.
How does dye testing work?
A small amount of dye is released near suspected leak points (skimmer joints, light fittings, shell cracks). If a leak is present, the dye is drawn into the leak path and visible as a stream. Dye testing is most useful for confirming a leak at specific known suspect locations after sonar has narrowed the area.
What about leaks in the return or suction lines underground?
We pressure-test each plumbing line individually using a system of plugs and a pump. A line that won't hold pressure has a leak. We can then trace the line to the leak point using acoustic equipment and either repair the line in place or, in older systems, reroute it.
How much does pool leak detection cost in the SGV?
Detection typically runs $300-$650 depending on pool size and the number of methods needed. Simple repairs (skimmer reseal, fitting replacement) range $250-$800. Line repairs range $800-$2,500. Shell crack repairs vary widely based on size and surface type.
Does drought policy affect pool leak repair?
Yes, indirectly. California's ongoing drought conservation guidance and LA County water restrictions mean that pool leaks waste water that is increasingly expensive and regulated. Many SGV homeowners now treat pool leak detection as a routine inspection rather than waiting for a visible drop, which is the right call.