Replacing a pump seal requires removing the plug that covers the motor shaft. Use a hook tool to hook the impeller to avoid it turning. When holding the impeller, turn the motor shaft screw counterclockwise and loosen the impeller. Remove the 4 through bolts that hold the motor to the wet end. These are usually 5/16″ heads that run all the way through the motor to the wet end. Once removed, the wet end falls off revealing the impeller inside and providing access to the pump seal.
Be sure to have ordered the right pump seal kit ahead of time for replacement once pump is taken apart. Insert the pump seal kit per directions that come with the kit and then replace the impeller and wet end, tighten through bolts and reinstall the pump.
The problem with pump seals is that they are susceptible to chemical damage by out of balance water. That is why it is imperative that the pH in a hot tub is kept between the desired range of 7.2-7.6 which is slightly basic. This keeps it out of the acid range and hence avoids eating at pump seals which in turn can cause a leak at the pump.
Regular inspection of spa pumps can provide early warning of a leaky pump seal and if the seal is replaced in a timely manner, pump replacement can be avoided.
Need a replacement wet end, you can get those too at Hot Tub Outpost USA.