I'm not home to look at it but to the best of my recollection, the difference is that the porcelain has a cast-in pass through that allows both the bidet water supply and electrical cord to drop down through the porcelain rather than drape off the side.
This arrangement makes the water supply line virtually unnoticeable. The electrical cord is still visible because the electrical outlet has to be roughed-in just outside the metal frame of the carrier. But again, the cord is routed from the bidet seat down through the pass-through in the porcelain and then over to the outlet.
I did recently see a unit that completely concealed both the electrical and water connections but as I recall, it was stupid expensive; in the several thousand dollar range. Maybe Kohler? I just can't recall.
Thanks for more information. Here is what I have understood until now:
- As you said, the Toto AP toilet porcelain has a hole through which the bidet and electrical cord will pass through. It doesn't matter whether a Geberit or Toto wall carrier is used with it. However, it does matter whether a Toto Bidet seat versus some other manufacturer is used with it. Toto designs their bidet for the connection to go through this hole. Biobidet has electrical and water connection on two sides of the bidet - so definitely cannot hide both. Brondell bidet has the potential for its connection to go through this hole but they don't know - they should be researching this kind of compatibility stuff. I believe that the EP toilet has a similar hole. Also, when buying the toilet - you can buy the toilet with/without the hole - so you have to be careful.
- Toto has two different carriers that can be used - WT173M and WT173MA. Both of them have the tubing that will ultimately connect to the bidet. WT173MA also has an additional connection to the S550E bidet for the autoflush - i.e. if somebody is buying the S550E for the autoflush capability, they must buy the higher priced WT173MA carrier to work with it but otherwise stick to WT173M.
- Geberit 111.902.00.5 (1.28/0.8GPF), (2x6 construction) is compatible with the AP toilet. However it doesn't have the water connection for the bidet. That can be had with part 249.801.00.1. However, that part is not really necessary - the plumber can directly add another water line for the bidet - definitely true for new construction. Geberit does not have the autoflush connector.
Geberit wall carrier price is all over the place. Even though the list is $672, I have seen a couple of places sell for below $300.
But ignoring the price of the wall carrier, I am thinking of the AP toilet with C5 bidet seat and Geberit carrier - seems like they have been building carriers for a while - hoping for longer reliability and let the builder add the additional water connection for bidet during construction. All told, should be around the $1500-$1600 price range (without installation).
As you said - there are other things out there that are fancier but somehow the price seems to increase exponentially with every little feature. The salesperson even mentioned a $5,000 toilet - probably just priced for the bragging rights for for people who have money to flush down the drain
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