It's an easy DIY job to replace the lamp and service an Excelight Ultraviolet System.  Just follow the steps below:

1) Unplug the system from the electrical outlet and turn off the water supply to the unit and release pressure by opening a faucet until water slows to a trickle.

2) Carefully remove the lamp connector from the electrical end cap assembly to just expose the top of the UV lamp. While holding the lamp base firmly, disconnect the lamp 4-pin connector by pulling off lamp. Lamp base can be very hot - be careful not to drop the lamp into the quartz sleeve as both are easily broken.

3) Carefully slide the lamp out of the quartz sleeve and discard.

4) Loosen and remove both end caps. Roll back the o-rings at both ends and remove. Carefully extract the quarts sleeve from the reactor housing. The quartz sleeve is very fragile and is easily chipped or broken - use extreme caution when installing or removing it from the reactor vessel. NOTE: Do not touch the lamp or quartz sleeve with your fingers. Handle by the ends only or wear soft non-abrasive gloves.

5) Clean the quartz sleeve with vinegar or a scale-removing product. (Lime Away, CLR)

6) Examine the quartz sleeve o-rings. If they look worn or cracked, replace them and reinstall the quartz sleeve.

7) Install new lamp by reversing the procedure described in item #2 above, being careful not to touch lamp with bare hands

8) Slowly open shutoff valves and purge the air from the system.

9) Ensure there are no leaks at the end caps before connecting the power to the system.

10) Reset the UV Power Source. The Lamp Life Days (lamp change reminder timer for models built after February 2011) is reset by disconnecting the UV power source from the AC power supply, waiting for 15 seconds and then reconnecting the AC power supply with the push button depressed till screen displays “rSEt” followed by a short audible beep, the number “365” shows on the screen indicating that the reset was successful. (For models prior to February 2011 a three seconds beep indicates the successful power source reset)