my toilet is backed up

I have experiense. I agree the problem is frustrating. We bought a new Cameo, and one month later it was doing as you describe. Everything was checked. Finally dealer took it in and took apart. Sure as the world we had a pyramid. We were using an enzyme tank additive, but I've learned since if they freeze bad it kills the active enzymes. Dealer put U digest it, enzyme, and in 24 hours he was able to clean. He went and looked at my trade in and it had the same problem. I always use U digest it now, and only had a problem once because I let it freeze. Also still use a lot of water. Just like you my tank would drain, I would use the built in spray system, and fill and drain till it looked perfectly clean. Still the pyramid was there. Must use a lot of water, and an enzyme not frozen. Good luck. I feel your pain, and I'm not laughing!!!!!