A pool leak is a relatively common event. Most are relatively small leaks from relatively small sources. While the construction of the pool may appear simple, even the best-designed and built pool will ultimately develop leaks over time. There are a number of types and locations of leaks.


Pool leaks are common. There is a complex system of materials that form the pool and its equipment and each piece and all connections must be watertight. A typical in ground pool is a concrete shell covered by a plaster (DiamondBrite for example) surface, tile, and grout.


The concrete shell and its surface are penetrated to allow for the installation of other pool components such as skimmers, returns (sometimes called “jets”), the main drain, lights, and vacuums. Each of these components is then connected to the pool’s operating equipment. The operating equipment such as the motor, pump, filter, and controls are typically located away from the pool. Underground lines connect the operating equipment to the pool components.


Each of these pool features and components can leak over time. As the pool and its equipment ages various chemical and physical changes occur. Grout becomes brittle over time and can crack. A pool uses a surprising large amount of grout. Typical pools have tile rows at the pool’s waterline and may use tile in other underwater surfaces such as steps and ledges. Each of these areas is grouted between each tile. Grout cracks typically begin happening in pools 5 years old and older. These grout cracks and the amount of water leaked begin small and may be difficult for the homeowner to know if a leak is present or if water loss is due to evaporation. As the pool, and its grout lines age further more and larger cracks develop in the grout and pieces of the grout may begin to fall out. The amount of water lost due to these leaks can be significant.


Other pool components such as the skimmer, returns, main drain, lights and vacuums rely on both the component and the caulk being watertight. Specialty caulk designed for pool use is employed to secure these pool components to the pool with a watertight seal. Caulk, like grout becomes brittle over time and can develop cracks. These cracks can leak allowing water to flow through the previously watertight seal. Caulk leaks also typically occur in pools at least 5 years old. Caulk leaks can develop very quickly and can cause the pool to lose a very large amount of water.


Pool leak operating equipment can also contribute to pool leaks. The pool motor, pump, filter, and valves are all connected by PVC plumbing and epoxy sealants. The underground plumbing which connects the operating equipment to the pool is also made of PVC plumbing. All of the above ground PVC and epoxy are exposed to the weather and elements 24 hours every day. They are also exposed to the vibrations of the motor and pump 6-8 hours every day. Leaks develop as age related cracks in both the PVC plumbing appear. These leaks can begin small and gradually leak small amounts of water around the pump, motor, or filter. These can appear as persistent damp areas around the operating equipment. They can also be quite large and dramatic. When a PVC line breaks with the pool’s pump running a large flow of water is released. If not stopped this can empty the pool in a matter of hours.


Pool leak operating equipment, PVC, and sealant cracks produce two different types of leaks. These cracks may leak water or they may suction air into the system. The pool pump is the heart of the pool’s operating system. Like human hearts, the pump pulls water from on side and pushes water out the other side so that it circulates throughout the system. When a crack develops in the PVC or sealant of the equipment on the “Push” side water is pushed through the crack. The water flowing through this push side equipment and PVC is under pressure. Pools typically operate between 15 and 30 PSI water pressure. Lower pressures are best for the system and PVC. Higher water pressures place additional stress on the equipment and connections. Filters typically cause higher water pressures. Pool filters which are dirty or need replacement cause pressures to rise as the water can not flow easily through a dirty or damaged filter. A regular routine of filter maintenance and replacement helps avoid leaks.


Cracks that occur on the “Pull” side of the pump where water is being pulled to the pump will pull air into the system. The effect of the water being pulled through this side of the system will create suction around the pool leak. This water is also under higher pressure than the surrounding air so air is sucked into the system and travels through the equipment and plumbing along with the pool water. Ultimately this air is pushed into the pool by the returns. When this type of crack exists the returns will blow bubbles into the pool leak while the motor is running. These air leaks usually begin small but they grow. While a small amount of air entering the system does not usually have a significant effect, as the cracks grow the amount of air in the system increases. If not repaired, eventually the excess air will prevent the pool motor from priming and may result in an expensive burned out pool motor.


The final category of pool leak is underground leaks. These pool leaks are fairly rare but can be very serious and difficult to detect and repair. Underground leaks only represent 5% of all leaks. The PVC plumbing used in the underground lines that connect the pool to the pool equipment is not exposed to sunlight and weather. It is stabilized against vibration by the surrounding soil and does not experience large temperature variations. The effect of these factors is that the underground PVC ages more slowly and is significantly less likely to crack. However, cracks and leaks do occur and excavation of parts of your pool, pool deck, or yard may be necessary to correct them.