Bits of something from black tank

[MikeAronhalt]

Hi all. I dumped my black tank and it was very slow in draining. After I dumped many buckets of water into the toilet, it worked better. After flushing the sewer pipe, all this gunk came out. Kind of looks like rusted pieces and very brittle. Calcium deposits? The black tanks are plastic correct? We go camping about every 6 weeks here in Florida. After dumping, I always put in about 3-4 gallons of non-potable water and about 4-6 ounces of the orange TST Max toilet treatment from Camco. Attached is a picture of of the “gunk”. Anyone have any idea what is going on? Thanks.
2018 Sundance TT 221RB

 

[Golfish]

Well i doubt you have cast iron pipes . My guess is scum/hard water deposits and poo formed a coating on the tank and broke loose