Tools and Materials
Adjustable wrench (two preferred), PTFE thread seal tape, a shallow pan or bucket to catch trapped water when disconnecting supply lines, and a standard Phillips screwdriver for the timer. The Bosch Comfort System box includes the pump body, adapter kit (thermal bypass valve assembly), two braided supply hoses, mounting hardware, and a 24-hour programmable timer. Verify supply hose length (typically 12 inches) is adequate for your under-sink configuration; extension hoses are available at hardware stores.
Under-Sink Connection Procedure
Step 1: Shut off hot and cold angle stops under the sink. Step 2: Disconnect the existing hot supply hose from the angle stop; let residual water drain into your pan. Step 3: Install the Bosch adapter kit between the hot supply angle stop and the faucet hot inlet -- it intercepts the hot line and adds a port that connects to the cold water line. Step 4: Connect the thermal bypass tube from the adapter to the cold water angle stop or cold supply line using the provided tee fitting. Step 5: Mount the Bosch pump to the wall or cabinet interior using the provided bracket. Step 6: Connect the pump inlet to the hot water angle stop using one braided hose; connect the pump outlet to the adapter inlet using the second hose. Step 7: Open both angle stops and check for leaks at all connections.
Electrical Connection
The Bosch Comfort pump plugs into a standard 120V outlet. Most kitchens and bathrooms have an outlet under or near the sink for garbage disposal or similar; if not, a licensed electrician should add one before installation. Route the power cord clear of the drain and supply lines and secure with a cable clip to prevent chafing. Plug the pump into the timer module; plug the timer into the outlet. The pump is now powered and controlled by the timer schedule.
Timer Programming
The 24-hour mechanical timer has 15-minute interval pins around its dial. Press in the pins corresponding to your desired run times -- typically 5:30 to 8:30 AM and 5:00 to 10:00 PM. Pins that are pressed in correspond to ON periods. The timer clock sets by rotating the dial to the current time indicator. After programming, verify the pump activates and deactivates at the correct times during the first 24 hours.
Troubleshooting: Cold Water Coming from Hot Faucet
If cold water arrives at the hot faucet after installation, the thermal bypass adapter is not closing properly. Check that the adapter orientation matches the arrow direction marked on the body (flow direction). Verify the cold supply connection is secure and not cross-threaded. Allow the system to run for one full cycle -- the thermal valve calibrates on the first few cycles and may deliver slightly cool water initially until the valve seat learns the temperature differential.