In case people are needing full instructions:
(from Haywards Manual)
Servicing and Cleaning the Aqua Rite cell: Turn off power to the Aqua Rite before removing the electrolytic cell. Once removed, look inside the cell and inspect for scale formation (light colored crusty or flaky deposits) on the plates and for any debris which has passed through the filter and caught on the plates. If no deposits are visible, reinstall. If deposits are seen, use a high pressure garden hose and try to flush the scale off. If this is not successful, use a plastic or wood tool (do not use metal as this will scratch the coating off the plates) and scrape deposits off of plates. Note that a buildup on the cell indicates that there is an unusually high calcium level in the pool (old pool water is usually the cause). If this is not corrected, you may to have to periodically clean the cell. The simplest way to avoid this is to bring the pool chemistry to the recommended levels as specified.
Mild Acid Washing: Use only in severe cases where flushing and scraping will not remove the majority of deposits. To acid wash, turn off power to Aqua Rite. Remove cell from piping. In a clean plastic container, mix a 4:1 solution of water to muriatic acid (one gallon of water to one quart of muriatic acid). ALWAYS ADD ACID TO WATER - NEVER ADD WATER TO ACID. Be sure to wear rubber gloves and appropriate eye protection. The level of the solution in the container should just reach the top of the cell
so that the wire harness compartment is NOT submerged. It may be helpful to coil the wiring before immersing the cell. The cell should soak for a few minutes and then rinse with a high pressure garden hose. If any deposits are still visible, repeat soaking and rinsing. Replace cell and inspect again periodically.
I live in So Cal where the water hardness is off the charts. Keeping the pool balanced using the tips from this site (even only waiting for rain water dilution to bring down the hardness slightly), I have not had to use an acid bath to clean the cell. A high pressure hose off has worked until it hit the year mark today. I found some deposits on the outside of the internal cell frame. I split a paint stirring stick (plenty around from never ending house remodel) and was able to scrape off the deposits then hit the cell with another blast of the hose. Clean, installed, and reset in quick time.
Hope that helps!