How to Repair an Underwater PVC Pipe
Locating the leak on a submerged PVC pipe is difficult, but repairing the underwater leak can propose another set of difficulties. When PVC is submerged, the majority of epoxies and pipe repair wraps will not bond to the leaking area of the PVC pipe. The epoxies that do adhere to the PVC pipe are non-adhesive, meaning they do not stick directly to the surface of the PVC pipe and you need to remain in the water go keep the epoxy or pipe repair wrap on the pipe until it semi-cures.
Turn off the supply of water to the leaking PVC pipe by turning the supply valve clockwise.
Squeeze equal parts of the two-part underwater glue onto the piece of cardboard and thoroughly mix the underwater glue with the putty knife. The underwater glue needs to have a uniform color appearance to ensure that glue is mixed correctly.
Load the putty knife with enough mixed underwater glue to cover an area at least twice the size of the PVC pipe leak. If you are repairing a pinhole leak, you should use enough glue to cover an area the size of a quarter.
Apply the underwater glue to the PVC pipe with the putty knife, making sure you have thickly covered the repair area of the leaking PVC pipe.
Allow the two-part underwater glue to cure for 24-hours before you turn on the water to the repaired PVC pipe.