A boiler economizer is a device that is designed to increase the operating efficiency of a boiler, cutting down on its operational costs over the lifetime of the boiler.
Although the savings on any given day may be relatively small, the impact over time can be significant; some boilers are designed with economizers built in, while in other cases, an economizer can be fitted on after the act.
The boiler economizer acts as a waste heat recovery device, ensuring that this heat does not go unused. 
Instead, the heat is used to essentially preheat the water, so that less heat is required to bring the water to a temperature high enough to make steam.

Pls note :The economizer pipes is ok for customized