Michelle,
You can siphon off the sludge into a 5-gallon bucket, let the contents of the bucket settle out, then decant the electrolyte back into your cooker. Or, you can just dump the entire bucket. In my opinion, it is a good idea to "blow down" the electrolyte every now and then. Some undesirable ions, like chloride, build up and need to be purged periodically. Chlorides and stainless steel do not get along together. A rule of thumb is dump 1 or 2 gallons for every 10 gallons of water added to replace what has evaporated.
Jeff