Caroma trapway to drain connection

[El Conquistador]

Great advice on this site and I really appreciate all I've learned here.

I'm considering getting a Caroma toilet for my bathroom renovation and I had a question regarding the 4" trapway. The toilet being replaced is a 30 year old Kohler. All other discussions aside, my son clogs this old toilet regularly due to the large diameter of his BMs. I've become quite adept at using a plunger.

The existing waste drain from this bathroom is 3" from the toilet to the 4" main house drain. The potential reduction in size from the 4" toilet trap to the 3" bathroom drain is giving me some heartburn. Is it acceptable/safe/code compliant to reduce the size of the drainage system from 4" to 3" to tie to the existing system? And if so, where would be the best place to do this. I have never had a problem with the 3" system beyond the clogged toilet.

I'll also add that it wouldn't be that much of an issue to upsize this 3" bathroom drain, it is easily accessible, I just really don't want to have to go through the expense and headache if it didn't need to be done.

Thank for the advice. It is greatly appreciated.

 

[Reach4]

I think you would find that a modern toilet with the better-formed trapway is much more resistant to clogging than the older toilets. It is unlikely you would have the problem with a good modern toilet. The Caroma toilet with the big trapway may not be needed, but being extra-sure makes sense.

I was at first thinking you were exaggerating about the 4 inch trapway. I now see that is a thing. If you are going that far, then putting in 4 inch pipe for that to feed into makes sense. I am not a plumber.

 

[Sponsor]

 

[WJcandee]

Personally, I think it kind of obviates the point of the big trapway if you are going to kluge it down to a 3" drain. And if there's something that would clog a 3" drain passing through your 4" trapway, you're gonna be pulling that toilet a lot to get it out and/or snake your drain line. Why borrow that trouble?

For 99 percent of the population, the giant Caroma trapway provides no benefit; otherwise, all toilets would have it. And frankly you're just passing the clogging material down into your house piping in the same shape it went into the toilet. For the 1 percent that can benefit, it is the rock-hard consistency of the BMs that is usually the issue, not as much the diameter. Even so, if your son can generate a BM that can't pass through a 2.125" trapway (i.e. its diameter is indeed bigger than that), that would be surprising. I don't want to be gross, but I would measure before I bothered to rip out my plumbing to put in a 4" line, which I think you basically have to do if you want the Caroma.

My advice would be to just get yourself a good Toto. Even the entry-level Entrada is an excellent-flusher and non-clogger. And at plus or minus $200 (even less if you shop carefully and negotiate a little), it's a best buy.

 

[Terry]

The 270 bowl is sort of a folded 4" trapway. Not round, but does come out to a round 4" adapter.

The 270 adapter

The 270 bowl

The 305 bowl is a 3" trapway.

Caroma 305 bowl with 3" trapway

There are some that will plug the 2" trapways. The old 30 YO Kohler would have been about 2".

The TOTO will flush better with their 2" trapway and larger flush valve to push it. Some options are pressure assist or Caroma. The Kohler Highline with Flushmate is a good bowl with pressure assist.

 

[El Conquistador]

Thanks for the feedback and helping me to think this issue through.
Based on what I'm reading, I think I'll install the (more readily available) TOTO in at this time. If the clogging problems persist, I can always move the TOTO to the other bathroom and pursue the options with the Caroma or the pressure assist .

Again, thanks for the great information, I've been a lurker here for quite a while; glad to be a part of this community.