Black water tank

[Ace]

I have a 1998 Gulfbreeze Sea Hawk. The black water tank has given me problems since I purchased it 2 years ago. It does not want to drain it from time to time it would with a vaccum truck but I have it plumbed to a sewer system now and it is full or a least I think it is full to the toilet. Has anybody had this problem before? I havre used a rod to get it to drain a little but it seems that something is in the tank preventing it from free draining.
Any help would be appreciated.

[Nanaeve]

I've heard that far too many times the factory makes the cutout for the toilet that the plastic piece is allowed to drop into the tank and "forgotten". It then causes the type of problem you discribe. You might want to check it with a light and mirror next time its empty.

[Timothy]

You are leaving your valve closed until the tank is full, right? If not that is your problem. If the pumper truck can clean it out the vent must be okay.

[squid]

Howdy, I also have a black water holding tank issue, won't drain. I'm meeting a man monday at camping world in troutdale oregon.
Hopefully he'll get it fixed, I'll keep you informed. Sincerely Sidney FW