Once a year prob'ly won't hurt, but...
You're not really accomplishing any more--except in your mind--than you would with plain water either...'cuz bleach doesn't clean, it just kills a few critters and turns dark stuff white. Nor does it break down any of the "goo." You just don't see it any more 'cuz it's no longer black. It's also not a good idea to put a whole gallon of bleach into your holding tank...urine is high in ammonia...it shouldn't be combined with chlorine in large doses. (Before anyone asks, there isn't enough chlorine in munipal treated water to matter). A better way: stick the intake hose in a gallon of water liberally laced with Raritan C.P. Pump until it runs out the rim, then stop and let it sit for a few hours--to let the enzymes in C.P. do their stuff...overnight is best, and you could even abandon it for a day or two--C.P. doesn't have anything in it that can hurt the plumbing...any longer, and what's in the rim will just evaporate. Finish pumping the rest of the gallon through...follow with a thorough clean water rinse...and follow THAT with a pint of undiluted white vinegar. The C.P. will clean out the "goo," and the vinegar will dissolve any sea water crystals in the hoses and the channel in the rim of the bowl. Best time to do this is in the fall, just ahead of winterizing. And if you blow the intake hose and rim out with air after you're done and leave it disconnected from the intake thru-hull, you won't need any antifreeze in 'em.
