I want to install a water softener for my house.I am using a salt based softener now which requires me to change salt frequently.Is there any salt free and low maintenance softener exists ,is it effective and how do they work?
The only thing that comes to mind for a practical "salt-free-softener" is a Reverse Osmosis (RO) system. You could also distill the entire water supply, but it's not practical unless you happen to be sitting on a lot of excess power/heat.
An RO system is rather costly and wastes a considerable quantity of water, so they are more commonly used for drinking & cooking water rather than for the whole house. The principle of operation is that the water is forced through a membrane that does not allow dissolved minerals to pass through it, but a significant amount of water has to be diverted to carry that material off.
I don't think they normally are set up this way, but it's always seemed to me that the waste-water from the process could be collected and used for toilet-flushing, irrigation or the like.
Depending on the age and condition of your salt-based softener, and the hardness of your water, you might find that you can reduce salt use considerably with a more modern unit - many older units simply recycle on a time switch, while newer ones actually pay attention to the amount of water used.