Anyone who has been delegated the task of cleaning the swimming pool  knows that purchasing an automatic pool cleaner is money well spent. Automatic pool cleaners move along the floor of the swimming pool sucking up trash and debris while you sleep, so the job of pool cleaning is greatly reduced.  Some pool cleaners will even climb the walls of the pool removing loose debris and scrubbing the pool surfaces. Automatic pool cleaners come in three different varieties: Suction Side Pool Cleaners, Pressure Side Pool Cleaners and Electric Robotic Pool Cleaners
   

Automatic Pool Cleaners - Pressure Side: An automatic pool cleaner that’s pressure side oriented is driven by water pressure from the pool pump itself which actually drives the pool cleaner around the pool collecting trash into the collection bag.  This type of cleaner or pool vacuum may be ran by the main pump, or from an individual pump dedicated just for this purpose.  Positive attributes on a pressure side automatic pool cleaner would be that it affords one more time in between pool filter cleanings.  This is due to the fact that the pressure side cleaner doesn’t allow trash to be pulled into your pump basket or pool filter.  Obviously, the automatic pool cleaner that operates on water pressure would be the route to go if your pool is surrounded or has trees nearby.

"Pros" of the dedicated pump - The overall suction power of your automatic pool cleaner will be intensified allowing the pick-up of larger debris, all around improved pick-up and collection into the cleaner bag.  

"Pros" of the non-dedicated pump - Cost of pool cleaner type should be less expensive.  Installation cheaper due to less components (booster pump and dedicated line for cleaner) All trash collected is deposited into the automatic pool cleaner bag.  Collection of larger trash more efficient.  Provides ease in filter maintenance.   

Automatic pool cleaner - Pressure-Side "Cons": Does not act as a moving filter suction device.  Allows small particles of dirt and sediment through.  Does not do a thorough job in cleaning/scrubbing walls of pool.

Automatic Pool Cleaner/Suction-Side: What drives this type of cleaner to move about the pool and vacuum as it goes is suction itself.  This cleaner works as a moving filter.  A bonus to this type system is as it is cleaning it brings water in taking it through the filtration system.  This provides a quicker water turnover in less time.

As far as scrubbing walls some of the suction-side pool cleaners actually agitate as they maneuver around the pool producing a scrubbing action.  As the cleaner is scrubbing and losing tiny particles these are sucked down and enter into the filtering system.  This method removes much smaller particles than a pressure-side cleaner that deposits debris into the cleaner bag.  No installation of additional plumbing or pumps is necessary therefore, this type of cleaner would be a lot less expensive to install.

Suction side automatic pool cleaners operate off the suction created by the pool pump. They are usually connected to a skimmer in the pool and as they move along the pool floor debris is sucked up and trapped in the swimming pool filter. If your pool is such that gets a fair amount of leaves and larger debris in it, the filter and pump basket will need to be cleaned regularly using this type cleaner. On the positive side they are capable of removing smaller particles much better than pressure side cleaners that use a net type bag to contain the debris they pick up.

Robotic automatic pool cleaners are self contained units that run off electricity. They have a power pack that is plugged into household current, the voltage is reduced to avoid electrical shock , and the robot is powered by built in motors. Most robotic cleaners have brushes on them and actually scrub the pool walls and floor. Some robotic pool cleaners have on board computers so it can (learn) the shape of the pool to more effectively clean all areas. Robotic cleaners catch all the trash and debris they remove in a self contained filter. The true advantage to these type cleaners is the scrubbing action. No more walking around the pool scrubbing the walls. Robotic pool cleaners are the most expensive of the three but for the job they perform you may decide it’s a great investment.  

The Robotic pool cleaners vacuum debris into the self contained filter via a separate pump located inside the cleaner.  Typically there is a computer chip located on board the robot enabling diagnostic measures to discern any technical issues with the cleaner.  This chip is also responsible for aiding the memory of the cleaner with such things as "shape of the pool".  A remote control comes with some units allowing the robotic pool cleaner to be manually directed to areas for cleaning that may have been missed.

Unique to the Robotic pool cleaner is the fact they not only scrub the walls; but, clean the tile line as well.  As previously mentioned there is a self contained pump inside the unit that vacuums trash and debris.  As an added benefit this helps to supplement the water circulation.  While the automatic robotic pool cleaner is the most costly it is an excellent purchase in the long run.  This type of pool cleaner is one of the best in picking up small particles of sediment, sand or small debris.

Robotic pool cleaner "Cons": Not withstanding the price range Of $700 to over $2,000, if there is a systematic problem with the cleaner you would possibly need to ship it to an authorized service dealer or back to the factory.  Another issue could be the fact that it is the manufacturer’s recommendation to remove the cleaner from the pool following each use.

This about sums it up on the various types of automatic pool cleaners.  I have tried to convey the merits/shortcomings of each type of unit.  Hopefully this information will assist you in selecting the right pool cleaner for you and your family.