What is lost when condensate is dumped
Condensate is the water left after steam has given up its heat, and it is still hot. Send it to drain and three things go with it: the remaining heat, the water itself, and the treatment chemistry that made it boiler-feed quality.
The make-up water replacing it is cold and untreated, so the heat has to be produced again and the water conditioned again. In effect you pay for the same water a second time.
Where condensate stops returning is usually a steam trap
A steam trap passes condensate and holds back steam. It can fail in two directions: stuck open it blows live steam, stuck closed it backs condensate up and kills heat transfer. Neither is visible from the outside.
So traps get checked on a schedule, by ultrasonic listening or temperature measurement. In an unchecked system the proportion of failed traps grows quietly over time and fuel consumption rises without an obvious cause.
The return line is designed too
A condensate line carries two-phase flow: water and flash steam together. Size it like a single-phase water line and it runs noisily, water hammer appears, and fittings suffer over time.
Flash steam is itself a usable resource. Directed to a low-pressure consumer it does work instead of venting to atmosphere — one of the improvements achievable in an existing plant with a relatively small intervention.
Insulation comes before recovery
Before recovering condensate, make sure the heat is not being lost along the way. An uninsulated steam line, or a valve whose insulation was never refitted, spends much of the gain before recovery can deliver it.
Removable points such as valves and flanges get opened during maintenance and their insulation often never goes back. Removable insulation jackets exist for exactly these places, and they deserve the same attention as the pipe run.