TOTO Plumbing Issue

[fled57]

Just finished remodeling both first floor bathrooms with TOTO Drake elongated ADA toilets installed. Toilets are installed back to back using existing double sanitary tee. When toilet is flushed, water in the bowl of the other toilet is partially siphoned out and preceded by a large air bubble. Bowl can be refilled by an additional flush. My plumber is dumbfounded and has no fix. Vent pipe is clear. Septic tank recently cleaned. Never had this happen before with my old 1972 toilets.

I spoke to TOTO tech service rep who recommended replacing the double tee with a double wye fitting for this G-Max toilet. Will this solve the problem?

Need some advice on how to fix this unacceptable installation.

 

[Herk]

The old 1972 toilets didn't move water as quickly as the Totos. What size is the vent?

 

[Sponsor]

 

[fled57]

I believe the vent pipe is 3 inch.

 

[MG]

Just finished remodeling both first floor bathrooms with TOTO Drake elongated ADA toilets installed. Toilets are installed back to back using existing double sanitary tee. When toilet is flushed, water in the bowl of the other toilet is partially siphoned out and preceded by a large air bubble. Bowl can be refilled by an additional flush. My plumber is dumbfounded and has no fix. Vent pipe is clear. Septic tank recently cleaned. Never had this happen before with my old 1972 toilets.

I spoke to TOTO tech service rep who recommended replacing the double tee with a double wye fitting for this G-Max toilet. Will this solve the problem?

Need some advice on how to fix this unacceptable installation.

My unprofessional opinion says the wye should fix it (and I think is also the recommended fitting because of the exact problem you describe) and you'll probably need a couple of 1/8 bends as well to get that setup right. The throat of the double ST is shorter than the wye and that's what is probably causing the siphon effect.

I'm happy with my Toto Drake on the redo of the CI line now...that thing flushes like a champ now that there is a clean run of PVC for it to empty into. I might replace the old AS in the smaller bathroom w/one down the road.

 

[fled57]

Just had the drain reconfigured. One Toto was changed to a wye fitting. Fortunately, access was in the garage, so minimal cost. Problem solved. Both Toto Drakes work like a charm.