In 2019, I got a call about a pool in Granite Bay that was losing 500 gallons a day. No visible cracks. No equipment problems. Perfect plumbing pressure tests. After two days of investigation, I found the culprit: a family of ground squirrels had chewed completely through an underground return line, creating their own personal water fountain 30 feet from the pool.

I’m Cooper from Pinnacle Pool & Spa Services, and after 10 years of tracking down leaks across Northern California, I thought I’d seen everything. Turns out, pools have more ways to leak than you’d ever imagine—and some of them are downright bizarre.

While most pool leaks come from obvious sources like worn gaskets or structural cracks, about 20% of the leaks I find fall into what I call the “you’re not going to believe this” category. These are the leaks that keep pool professionals humble and remind us that sometimes, the problem isn’t what—or where—you think it is.

Tree Roots: The Underground Menace

Let me tell you about the beautiful heritage oak in El Dorado Hills. The homeowners loved that tree—it provided perfect afternoon shade and looked gorgeous next to their pool. What they didn’t love was losing 200 gallons of water daily with no explanation.

That oak tree sat 40 feet from the pool. Seemed like a safe distance, right? Wrong. Tree roots can extend two to three times beyond the tree’s canopy, and they’re surprisingly strong. This particular oak had sent roots under the deck, around the pool, and eventually created enough pressure to crack the pool shell near the deep end. The crack was hairline—barely visible even when we drained the pool—but it was enough to create a serious leak.

Tree root damage happens two ways: pressure and penetration. Pressure damage is more common—roots grow, expand, and essentially push against your pool shell or plumbing until something gives. Penetration is rarer but more dramatic—roots actually grow through joints or existing small cracks, making them progressively worse.

Here’s what to watch for before roots become a leak problem:

• Deck lifting or cracking in a line pattern (following root growth)
• Tiles popping off in specific areas
• Plumbing that mysteriously clogs despite regular cleaning
• Consistent water loss near landscaped areas

Prevention is simpler than you’d think. Root barriers work well if installed properly—think of them as underground walls that redirect root growth. When planting new trees, follow my rule: keep them at least as far from your pool as their mature height. That 60-foot oak? Keep it 60 feet away. Fruit trees, Japanese maples, and most palms are generally pool-friendly if you must have trees nearby.

“Cooper was able to come out quickly and inspect my pool, he performed pressure tests to check the plumbing and also did a dye test throughout the pool, he ended up finding and repairing multiple leaks and at a reasonable price! Thank you sooo much!”

— Sofia Ramos, El Dorado Hills

Rodent Damage: More Common Than You Think

If you’d told me 10 years ago that rats would become a regular part of my pool leak vocabulary, I would’ve laughed. I’m not laughing anymore. Rodents—rats, ground squirrels, even gophers—cause more pool damage than most people realize.

My education in pool pest damage started with a Walnut Creek customer who couldn’t figure out why their automatic pool cover kept needing repairs. Turns out, rats were chewing through the $3,000 cover to get water during a dry spell. But that’s just the beginning. I’ve seen rodents chew through:

• Flexible PVC pipes behind waterfalls
• Automatic pool cleaner hoses (apparently they taste good?)
• Underground electrical conduits, causing equipment failures
• Spa air lines, creating mysterious bubbling

The signs of rodent involvement are usually there if you know where to look. Small, parallel bite marks on exposed pipes. Droppings near your equipment pad (yes, I look for poop as part of leak detection). Mysterious electrical issues that come and go. If your pool cleaner hose keeps developing holes in the same general area, you might have a midnight snacker.

Prevention involves making your pool area less attractive to rodents. Remove food sources (including pet food), trim vegetation away from equipment, and consider hardware cloth barriers around vulnerable pipes. If you already have a rodent problem, handle the pest control first, then repair the pool damage—otherwise, you’re just providing fresh chew toys.

Shifting Soil: Northern California’s Special Challenge

Northern California soil and swimming pools have a complicated relationship. Our expansive clay soil acts like a sponge—swelling when wet, shrinking when dry. Add our cycles of drought and heavy rain, and you’ve got soil that can’t make up its mind about where it wants to be.

I’ll never forget a Pleasant Hill pool that moved three inches over one winter. Not cracked—moved. The entire shell shifted as the hillside soil expanded with heavy rains. The homeowners first noticed their pool deck pulling away from the coping. By spring, they had a legitimate lean to their pool that you could measure with a level.

Soil-related leaks develop slowly, giving you warning signs if you’re paying attention:

• Doors or windows in nearby structures starting to stick
• Cracks appearing in your deck following a pattern
• Pool deck separating from the coping
• Water level dropping more on one side than the other
• New cracks in surrounding hardscape

The frustrating part about soil issues? The leak is just a symptom. You can patch the crack, but if the soil keeps moving, you’ll get new cracks. Sometimes the solution involves drainage improvements, soil stabilization, or in extreme cases, underpinning. It’s complex stuff that often requires engineering expertise beyond pool repair.

“I highly recommend Cooper at Pinnacle Pool and Spa Service. He recently performed a complex leak repair for me, including a leaking underground pipe. Aside from being a pleasure to work with, he is knowledgeable, thorough, reliable, hard-working, honest and reasonably priced.”

— Jon Chang, Walnut Grove

The Weird Ones: Stories from the Field

Some leaks defy categories. These are the ones I tell at pool industry conferences and nobody believes me until I show photos.

Lightning strikes: An Auburn pool where lightning hit a nearby tree, traveled through the ground via rebar in the pool shell, and created a series of pinhole leaks throughout the structure. The pool looked like someone had poked it with needles from the inside. Took us three days to find and seal all the tiny leaks.

Construction vibration: New home construction 100 yards away used pile drivers for foundation work. The vibration traveled through the ground and created multiple cracks in a 20-year-old pool. The homeowner thought it was coincidence until we mapped the crack pattern—all on the side facing the construction.

Gopher engineering: Different from surface rodents, gophers go deep. One in Napa Valley created a tunnel system that undermined an entire shallow end, causing it to settle and crack. The tunnel network looked like a subway map when we excavated.

Ghost equipment: Previous owners had buried old pool equipment instead of hauling it away. Years later, the metal rusted, soil collapsed into the void, and created a sinkhole that cracked the nearby plumbing. The current owners had no idea there was a pump and filter buried under their deck.

How I Track Down Mystery Leaks

When the obvious causes don’t pan out, it’s time for detective work. At Pinnacle Pool & Spa Services, we use several methods to find even the sneakiest leaks:

Pressure Testing: We isolate and pressurize individual plumbing lines to identify which ones hold pressure and which don’t. It’s methodical but effective.

Dye Testing: Still one of the best methods for finding structure leaks. We use special dye near suspected areas and watch where it gets pulled.

Sonar Detection: For those hard-to-find leaks, sonar equipment can detect the sound of water escaping, even underground.

Helium Testing: For the really tricky ones, we inject helium into pipes and use detection equipment to find where it escapes. Helium molecules are tiny and escape through even the smallest leaks.

Want to learn more about our professional leak detection methods? Visit our leak detection services page for detailed information.

The key is being systematic. Random testing wastes time and money. We start with the most likely causes and work our way to the unusual ones, documenting everything along the way.

Prevention and Early Detection

The best leak is the one that never happens. Here’s my simple annual inspection checklist:

Spring: Check for winter damage, inspect coping and tile, look for deck separation

Summer: Monitor water loss during peak use, check equipment pad for leaks, inspect skimmer and returns

Fall: Clear drains before rain, check for cracks before wet season, trim back vegetation

Winter: Watch for soil movement, monitor unusual water loss, check for storm damage

You can perform your own preliminary leak detection too. We’ve created a guide for at-home pool diagnostics that walks you through the bucket test and other simple checks you can do yourself.

For landscaping, stick with pool-friendly plants. Avoid trees with aggressive root systems like willows, poplars, and large oaks near pools. Keep irrigation zones away from the pool shell—you don’t want to create soil movement by overwatering one area.

What These Unusual Repairs Might Cost

I always hesitate to talk prices because every situation is unique, but I know it helps to have ballpark figures. Keep in mind these are general estimates—your actual costs may be less depending on the specific situation:

Tree root damage: Typically ranges from $2,500-$8,000 depending on extent and location

Rodent damage: Usually $500-$3,000, depending on what they’ve chewed through

Soil-related issues: Varies widely based on engineering requirements

These figures are just general guidelines. Many repairs cost less than these ranges, and we always provide free estimates so you know exactly what you’re looking at before making any decisions. Contact Pinnacle Pool & Spa Services for an accurate assessment of your specific situation.

“Best and most knowledgeable pool person that I’ve ever had work on my pool. He fixed my pump and fixed a leak in the pool. Fast, efficient and affordable.”

— Steve N., Loomis

What to Do If You Suspect an Unusual Leak

First, don’t panic. Even the weirdest leaks usually have solutions. Document everything—take photos, measure water loss, note when it started and any recent changes around your pool. This information helps tremendously in diagnosis.

Try the bucket test to confirm you actually have a leak versus evaporation. Place a bucket on your pool step, fill it to match your pool level, mark both levels, and check after 24 hours. If the pool drops more than the bucket, you’ve got a leak.

Most importantly, get professional diagnosis sooner rather than later. Water loss isn’t just expensive—it can undermine your deck, erode soil, and create bigger problems. The sooner we identify the cause, the less damage occurs and the simpler the fix.

Your Pool Has Stories to Tell

After 10 years of finding bizarre pool leaks, I’ve learned that every pool has its own personality and challenges. That gorgeous oak tree, those cute ground squirrels, even the soil your pool sits on—they’re all part of your pool’s ecosystem, for better or worse.

The good news? Unusual doesn’t mean unfixable. I’ve yet to meet a leak I couldn’t eventually track down and repair. Sometimes it takes detective work, occasionally it requires creative solutions, but there’s always a way forward.

Your pool is talking to you through small signs and changes. Learning to recognize those signs—whether it’s a slight deck separation or unexpected water loss—can save you thousands in repairs and countless gallons of water.

If you’re dealing with mysterious water loss or just want peace of mind about your pool’s condition, we’re here to help. From basic leak detection to solving the truly bizarre cases, Pinnacle Pool & Spa Services has the experience and equipment to get to the bottom of any leak.

Contact Pinnacle Pool & Spa Services for professional leak detection:

Sacramento Area: (916) 530-2096 | Bay Area: (925) 849-6545 | Toll Free: (888) 994-7665 (POOL)

Professional leak detection and repair services throughout Northern California. Using advanced techniques including pressure testing, sonar, dye testing, and helium detection to find even the most unusual leaks. Free estimates available.