While surface repairs may be adequate—and certainly cheaper for the customer—a better repair is possible if the entire depth of the crack is filled and sealed with epoxy or urethane. Low-pressure crack injection methods provide this solution and fit the lucrative ‘middle-ground’ option. It gives the customer a lasting repair, but does not involve extensive and expensive concrete modifications.
This method requires the pool to be drained and the surface of each side of the crack to be dry. Special injection ports are adhered to the surface of the pool, over the top of the crack at 300- to 450-mm (12- to 18-in.) intervals. The crack is then covered with the same epoxy to close it and prevent the injected sealant material from draining back into the pool.
Once the surface epoxy has cured, injectable urethane foam is forced into the crack through the injection ports using a special, dual-cartridge gun that maintains a constant pressure of approximately 0.275 MPa (40 psi). The constant pressure and low viscosity of the injection material, before it cures, ensures complete crack penetration.
The foam then expands up to seven times it’s volume, filling not only the crack, but also any voids behind the pool shell. (Injectable epoxy can also be used for this step, however it may require more material and may not completely fill the crack.) After the foam has cured, the ports and surface-seal epoxies are removed using a portable grinding disc. The crack is v-cut and a cosmetic layer of plaster repair compound is used on top.
While low-pressure injection offers the ability to perform permanent repairs, this method can also be adapted to provide some benefit for more serious problems. For example, in situations where future crack expansion is anticipated, the best way to spread this force over a wider area is to install staples or ‘stitches’ across the crack at 200- to 300-mm (8- to 12-in.) intervals.
Staples are made of high-tensile-strength material, such as rebar, stainless steel or carbon fibre. These staples are imbedded into the concrete below the plaster surface with special epoxy before the injection process. The staples and epoxy are covered with the same plaster repair compound used to fill the v-cut of the crack.
Once the pool is drained, a basic 3-4-meter (10- to 15-foot.) crack injection repair can generally be completed in about a half a day. The staple process will add another half day. Pricing is generally based on the job, as this repair will last longer than a simple surface fix.
Another common structural leak, which develops between the skimmer throat and the shell of the pool, can also be fixed with injectable urethane foam. These leaks are often repaired with putty; however, it must be replaced annually. For a permanent solution, the water level should be lowered below the skimmer opening before injecting the expandable foam through a pre-drilled hole in the bottom of the skimmer throat. Any void around the skimmer body is then filled, permanently sealing the leak from the backside. This repair method is more permanent than putty, but less involved than a complete skimmer replacement. It also provides a profitable yet affordable alternative for the leak professional and pool owner.
Calling in a specialist
It is important to keep in mind cracks can indicate a more serious problem. Those who are new to finding and repairing leaks should not hesitate to seek a second opinion from a more experienced builder or structural engineer when faced with a questionable repair. Once familiar with the types of cracks common to a particular area, it will be easier to suggest and deliver effective repair solutions.
Lance Anderson is the owner of Anderson Manufacturing Co., Inc., in St. Paul, Minn. He has been providing leak location and repair solutions to the pool industry for over 20 years. He can be reached at firstname.lastname@example.org.