The Polaris 280 pressure side cleaner and booster pump is what I like to install on old pools without dedicated cleaner ports, or an in ground cleaning system. There are products available that will allow you to run a cleaner using the skimmer at a low cost, but this often makes the pool more labor intensive. What do I mean by labor intensive? Products like the Zodiac Flow Keeper render the skimmer useless as the basket has to be removed to plug it into the suction hole.
With out a skimmer, nothing skims debris from the surface of the water leaving a less attractive pool and more netting for you. There is very little control over the cleaner with this kind of device. The Vac Mate is another product that allows you to run a cleaner. Its a step up from the flow keeper, because it has a basket and a tiny weir gate that retains the function of the skimmer. There is even a valve providing control between the cleaner suction and the amount it skims. However, these are press fit hose connections that wear out and come loose. The water level has to be kept higher to keep these press fit connections under water so they dont leak. The gasket stretches out frequently and needs to be replaced. Over time, the pressure cracks the body of the vac mate too. Any of the above stops the cleaner from working. It is a nice product and one I've sold many times, however both the flow keeper and Vac Mate restrict water flow, forcing the water to run thru the 3/4" hole at the cleaner and 30' of cleaner hose and can make the pool more difficult to care for.
A better way is running a cleaner off the return side of the system with a booster pump. This increases water flow dramatically by using the pools drain and skimmer instead of the restricting water through a hose and a cleaner. The Polaris cleaner shoots water out of its tail, stirring up dirt so the pool drain and skimmer can take it out. The cleaner is very fast and it only takes 4 hours to do its job. Depending on the model, there are 2-3 jets of water shooting up inside the body of the cleaner. This creates a vortex that sucks up large debris into the collection bag. The Polaris cleaner does an incredible job of keeping the pool clean while allowing the system to draw from the skimmer and the drain, increasing water flow instead of restricting it.
The Booster pump runs off a 3/4" flex line that is fed from the return side plumbing after the pool filter. It can be tied into an existing 1.5" return line to the pool or the 3/4" aerator line. I prefer to use the aerator line because it is the easiest way to retrofit an old pool with out taking away a return jet. This pump is very small and very efficient. It only needs to run 4 hours a day and draws very little power.
There are less expensive pressure side cleaners available, but they do not have a booster pump. The return eyes on the pool are important for water circulation in the pool and directing debris toward the skimmer. The cleaners that use a return eye are fine in some cases as long as there is still enough water movement left once a port is sacrificed. If the pool has 4 return eyes and after one is taken away there is still 3 remaining that's okay. Many old pools only have 2-3 return eyes and using a pressure cleaner that runs off one of those affects the water circulation in the pool enough I don't use them. The booster pump ensures the cleaner has enough water pressure to run at optimal performance with out effecting water flow in the pool on the suction side, or return side when the 3/4" aerator line is used.
The Polaris has a back up valve in between the wall and the cleaner. Every so often, the water will stop running to the cleaner and instead, shoot out from this valve. The cleaner is picked up, and pulled backward for about 10 seconds. This ensures the cleaner will never get stuck.
This cleaning system is not inexpensive, but it is one of the best options for old pools with out automated cleaning systems.