Determine the type of leak. Leaks can occur from a leak in the spa shell or though one of the jet bodies that blows air or water into the spa.
Insert dye or food coloring into the water, and observe the water flow of the dye. The dye will follow the flow of water to where the leak is located.
Perform a water level test on the pool spa. Fill the pool spa with water, and mark the level with a crayon or other mark that easily can be removed. Turn on the spa, and let it sit for at least 24 hours. You should locate the source of the leak above the level at which the water stopped dropping.
Repair any cracks in the acrylic shell using an acrylic repair compound. (See Resources.) Apply the compound to the crack, and let it dry. Refer to the instructions with the repair compound for proper use and application instructions.
Replace the gasket if the leak is at a jet body. A pool spa jet body has a gasket that is tightened to the inside surface of the acrylic shell. If the gasket has gone bad, it will need to be replaced.
Access the jet gasket by removing foam insulation or any plastic fittings that surround the jet.
Disconnect the jet from the inside of the acrylic shell using a socket wrench. Take off the old gasket from the jet, and insert the new one.
Reattach the gas jet, and tighten it using the socket wrench. Apply caulk or silicone sealant around the outside of the gasket and acrylic shell to prevent future leaks from occurring.