Decalcification

Chalk is a form of limestone. It's white & porous and is composed of the mineral Calcite. It's that Calcite that's responsible for clogging the pipes. It's dissolved in water and if you don't want clogging, the trick is to keep it dissolved.

One way to beat chalk an lime residue is using chemicals. A cheap and fairly harmless tip is using white vinegar. if that doesn't work, you can buy commercial products that are both stronger and far more harmful to the environment and your own health.

A second problem is if the affected area isn't reachable. For some applications, commercial tabs are available to fix this (toilet, washing machine, dishwasher), but if no specific product is available (example: pipes, pumps, boilers), you'll have to resort to other means.

Water softeners are placed where the water comes into the system. The tricks with a softener is it replaces the calcium and magnesium ions in the water with sodium ions. Sodium doesn't have the bad habit of clogging up the pipes. The water is run through a zeolite, a chemical matrix covered with sodium ions.
When the water flows past the zeolite, the calcium ions swap places with the sodium ions and the water no longer contains dissolved chalk.

Obviously, when the sodium ions run out, the machine has no use. They can be recharged by draining them in a bunch of sodium ions. Most machines use salt for this. Waste products by the machine are then the salty water used to soak the zeolite.

Clear disadvantage with this approach is the fact a machine can run out and will no long do what it is supposed to. And advantage is that the water actually contains less chalk, this isn't the case with the next solution.

Another solution to chalk problems is a way of making sure the chalk won't settle on the pipes.
An example of such a device manufacturer is Cleantronics.
Their devices generate an electronic and ultrasonic pulse, causing the free Ca++ ions to bind and structure into a strict pattern. This pattern makes the ions unable to tie to any other material (like pipes).

An advantage of this solution is the device only needs electricity, nothing more. it also doesn't need to be regenerated or refilled. The method is environment friendly and doesn't change the chemical compound of the water in any way.

A disadvantage is that the chalk is still in the water. So appliances like aquariums that require soft water will not benefit from this.

Cleantronics devices are usually placed in industrial or bigger appliances.