Which system is controlled based on a preset time interval for regeneration?

The correct answer is Timer Controlled because this type of system initiates regeneration based on a predetermined time schedule, irrespective of water usage. It operates on the principle that after a set period, the system will regenerate itself to maintain optimal performance. This is particularly beneficial in scenarios where water usage is relatively consistent or predictable, as it ensures that the system is regularly refreshed and operating efficiently.

Regarding the other options, the Brine Tank Float Control manages the level of brine in the tank and does not dictate regeneration timing directly. Demand Flow Controlled systems determine regeneration based on actual water consumption rather than a fixed time interval. A Contact Tank is involved in the treatment process but does not specifically control regeneration schedules based on time intervals. Thus, Timer Controlled systems stand out as those that specifically rely on preset timing for initiating regeneration.