New toilet selection for double santee fitting.

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Jm66208

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Need to replace two toilets in back to back installation that uses a cast double san tee. 1920's house & both baths have been remodeled, except the original cast iron stack was left in place, and the old toilets.:confused: Room below has coved ceiling & ornate plaster moldings. I suspect that's why they never replaced the cast iron. Closet bends are both 4" ABS.
Toto advises against this setup, but I have no choice. Do I look for "slow flush" toilets, or use Toto's & hope for the best?

back_to_back_kohler.jpg

Kohler Advice for the new toilet.
 
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Terry

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I would look for something with a 2" flush valve.
I have used a TOTO with 3" on a double fixture fitting, which is inbetween the two fittings shown above. The water will still skip across on a back to back and force a bit of water out the other bowl.
I have not done that with a double santee.

 
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Jadnashua

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FWIW, older toilets used lots of water, often nearly filling the bowl, before the weight of that water caused then to start to siphon and flush. Since there are regulations that reduced the amount of water that can be used for a toilet to flush, most get the siphon started in a different manner - a large flush valve and a siphon jet that gets a shot of water rushing out the outlet that then helps start the siphon, and therefore clear the bowl. Going down in flush valve sizes means less water can get out at once, and a likely decrease in flush efficiency. So, depends on your typical usage habits (like how much TP is used, how big and hard the deposit is) whether there's enough oomph to really flush the mess down the drain. You will have a hard time finding a good flushing toilet that can perform as well as one with a larger flush valve, and depending on your actual needs, it may or may not solve your issue about skipping over. This is not a Toto unique situation...it is shared by most (all?) modern toilets with larger flush valves and probably all pressure assisted ones.

Terry has a fair amount of info on his storefront...I'd start there. Toto, last I checked, still makes a few with a 2" flush valve. You may or may not be satisfied with their installation in your situation. Someone sitting on the opposite toilet when the other is flushed may be in for a surprise, and a lowered water spot in the toilet may affect its ability to flush since, instead of starting full, some of the water released during a flush has to fill the bowl to 'design' level, before it can then start the actual flush action. That may or may not happen, sometimes requiring a second flush to clear the bowl from the now full bowl.
 

Terry

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It pushes a column of air ahead of the water. It pushes the water upward in the bowl slightly, which allows water to slip up and over the high point of the trapway bend and down the drain. The more times you flush the opposite bowl, the more is lost.
It's not too bad if both bathrooms are used equal number of times.
 
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