I strongly recommend contacting a professional when it comes to this type of swimming pool maintenance. The following is for educational purposes only and in no way do I recommend attempting to replace your automatic cover on your own.
In the world of in ground vinyl liner pools it is no secret that there are a couple of components that will need to be replaced from time to time. I would say that the biggest of these components is the liner itself. Typically a liner will last anywhere from 5 to 10 years. As with anything there are some exceptions to this. Depending on how a person takes care of their pool I have seen liners that are anywhere from twelve to fifteen years. Conversely I have replaced liners that were a mere two years old. There are several variables that come into play that can affect the life of a liner. I can remember one specific example in which I replaced a liner that was only a few weeks old. That one was a result of a lot of holes put in the liner from the son of the home owner. He and his friends thought that it would be fun to use the telescopic pole and attempt to pole vault over the pool. This resulted in many many holes in the liner at the bottom of the pool. They may have been able to be patched but the homeowner insisted that the liner be replaced. The point of all this is to show that there are variables that come into play.
The other larger item that will need to be replaced from time to time is the automatic cover. It is important to understand that not all pools have an automatic cover. However homeowners with pools that do have an automatic cover will have to have them replaced from time to time. The life of a cover is similar to that of a liner, and will be subject to the same variables that affect their life. There are a couple of things that play a larger role on the cover than they do on the liner. One is the sunlight. Sunlight will start to fade the color of the cover itself and the UV rays from the sun will begin breaking down the material. Over time the material will become more and more brittle and need to be replaced. The other thing that will affect the life of the cover is the fact that it is a moving component. As with anything that moves it is subject to wear and tear as they say. This will result in a need to replace the cover as well. So how does a pool professional replace a cover?
This is a task that requires some know how and an understanding of how the cover functions. One thing that I always check is the condition of the pulleys. If it is the first time the cover is needing replaced then it is likely that the pulleys are still in good condition and will not necessarily need to be replaced. Next, the pool will need to be open. This will allow the installer to more easily remove the cover when the time comes to do so. The rope guides will need to be removed prior to removing the cover itself. The rope guides are located at the end of the tracks on both sides of the pool closest to the cover box. (The box is where the motor and reel are located) Once the rope guides are removed, the leading edge of the cover will be able to be taken out of the track. At this point I would cut the ropes as close as possible to where they attach to the cover itself.
The next step will require the help of another able bodied person. Now that the leading edge is free from the tracks and the ropes are no longer connected, the leading edge bar can be removed and the cover can be pulled out over the pool. Be aware that because the cover is no longer in the tracks it will likely begin to sink. Now that the cover is pulled out over the pool, it can be removed from the reel inside the box. Typically there will be several screws holding it to the reel itself. They will need to be removed and depending on their condition, they may be able to be used again on the new cover. Now that the cover is no longer attached to anything, it is ready to be folded up and disposed of. Again this part is easier with another person. Typically my helper and I will do this by pulling the cover off the pool three feet or so at a time folding it up accordion style as we go. This may take some muscle depending on how much water is sitting on it. Once the old cover is off we would begin the process of installing the new one.
Now what we have is an uncovered pool with the ropes from the old cover still in the tracks. We leave them there for the time being. They will come into play again while installing the new cover. Typically the new cover will come rolled up and wrapped in a piece of cover material. It will be laid out just behind the box on the deck. (Typically the deep end of the pool) Before we get that far we will make sure that the area is cleaned up and free of anything that may tear or scratch the new cover. From my experience most covers will have a warning label on them, usually in the center of the leading edge. This label should face up. If not then the cover is upside down and will need to be corrected. Once the cover is laid out the way it should be we would go on to the next step.
This is where the old ropes that are still in the tracks come into play. Both ends of the ropes will be protruding out into the box area one end is that which we cut free of the old cover, and the other end will be going through a series of pulleys and attached to the motor. The end attached to the motor will have to be removed from the motor and pulleys. This will give us two free ends of the rope on both sides of the pool. We will tackle these one at a time. Over the years I have learned a trick that makes running the new ropes a bit easier. Instead of removing the tracks from the wall, which is time consuming and can be a bit tedious, I will leave them in and just attach the new ropes to the end of the old ropes which are already in the track. To do this I use an awl, a propane torch, some string, some electrical tape, and some magic lube. First I take the end of the old rope that I cut from the cover, heat up the end of the awl with the propane torch, and push it through the rope about an inch from the end. The ropes are vinyl so when the hot awl goes through it the area around the awl will melt, leaving a nice open hole. I do this again with the end of the new rope. Now I will take my string and run it through each of the holes I made in the two ropes. I will then cut the string leaving enough excess to tie the ends together. It is important to butt the two ends of the ropes together rather than overlapping them. Once I have the string tied in a tight not I will wrap the ropes and string up with electrical tape. I want to be careful not to build up too much electrical tape around the ropes. I want to try and make the taped area not too much thicker that the ropes themselves. Now I will apply a good amount of magic lube to the taped area to make sure it slides through the track as easily as possible. Next I will pull the new rope through the track by pulling the old rope out. I will pull from the end that was previously attached to the motor. Once the taped area reaches the pulley at the other end of the pool it will become tougher to pull. With some steady and gentle pressure the taped area will slide through the pulley with the help of the magic lube, and become easier to pull again. If I were to pull too hard, the string would break and I would have to remove the track and feed the ropes through by hand. Once the taped area comes back out of the track in the box I can cut the old rope free of the new rope and now I have the new rope in place, and ready to be run through the pulleys in the box, cut to the proper length and attached to the motor again. This process will be repeated at the other side of the pool with the other rope. Once that rope is through it will go through the proper pulleys, cut to the proper length and attached to the motor.
Now I am ready to attach the new cover to the leading edge bar and insert it into the tracks. I will then replace the rope guides at the end of each track. There will be some slack in the ropes and I will again need the assistance of a helper to operate the switch while I ensure the ropes get wrapped up properly. Once all the slack is out of the ropes, my helper will continue to operate the switch to close the pool. The new cover will begin to slide out over the pool and I will go back and forth to make sure that the cover is sliding through the rope guides properly. Once the cover is entirely over the pool we are ready to attach the end to the reel again. Again depending on the condition of the screws we took out of the old cover, we will use them again to attach the new cover. If they are in bad shape I will use new screws to attach the cover to the reel. Once the new cover is attached to the reel I will have my helper start to open the pool. I will make sure that the cover wraps around the reel properly. After that it is a matter of running it open and close a couple of times to ensure that it is functioning properly.
As with anything regarding in ground swimming pools it is almost always best to leave it up to the professionals. There are many components and things that require experience to assess and properly address. In addition to that most reputable pool companies will guarantee their work so if something does happen they will come back and take care of it. I never recommend taking on anything of this nature by yourself. It is always best to leave it up to the professionals.