Toto Aquia II tank (ST416M) replacement - can I use an ST412M?

Discussion in 'Toilet Forum discussions' started by Brian Carter, Sep 11, 2020.

  1. Brian Carter

    Brian Carter New Member

    Joined:
    Sep 11, 2020
    Location:
    Philadelphia, PA
    Hi Terry (and community),
    I bought a Toto Aquia II a couple of years ago and just got around to installing it (bathroom remodel taking a long time, but hey, we're staying at home a lot more now, so I have time to work on it - my wife says I should have hired a plumber; she's probably right). So, I got the toilet installed on the floor, holes drilled in my new tile (that pained me), and the "interesting" installation procedure for the bowl all followed to a T, and it's down on the floor. Then I opened the tank, flipped it over to put the supply line on it, and wham-o!, discovered that there was a crack on the side of the tank. It's out of warranty, and I don't know if I cracked it or the Retailer or delivery guy did. So, off to buy a new one. Only, as you probably know, the Aquia II is discontinued, and I can't but a tank ANYWHERE. Even from Toto. The nice tech services guy at Toto told me that I'd need to buy a new toilet, but I asked if the ST412M would be compatible, because I knew where I could get one of those. So he told me he would take my info and email me once he found the answer. I haven't heard back yet. So I thought I'd try here to see if anyone has put an ST412M tank on a CST416M bowl, and did it have any issues. The specs match up on length, width, and height, but I don't know (and Toto couldn't yet confirm) whether the bolt holes will exactly match up. If the inner pieces are different, I don't care, because I can switch those out if needed, but the bolt holes have to match up exactly, I presume. I don't want to buy a complete new toilet for $400 or so if I can buy a new tank for $125 and get a working toilet. And now that the bowl is installed on the floor, I really don't want to be changing that out with one that's installed completely differently either (and I wouldn't know if it the skirt would cover my new holes in the floor until I put it down).

    So, long story short, can I use an ST412M tank on a CST416M bowl if my ST416M tank is cracked and I can't find a replacement?

    Or, in case anyone has an ST416M#01 in your inventory and are willing to sell it, I'd pay a fair price for it, plus shipping.

    Thanks for this forum! Loving the other advice that I've found here!
     
  2. Brian Carter

    Brian Carter New Member

    Joined:
    Sep 11, 2020
    Location:
    Philadelphia, PA
    Well, I never got an answer, even from tech support at Toto, so I had to go experiment and try to find an answer myself. Everything looked like it matched, so I ordered an ST412M (full kit, innards and all), but it arrived cracked. What I could find out, even with the cracked tank, though, is that the tank bolts appeared to match up - they might have been off by 1/4" or even 1/2", but they appeared close enough to make them work - there's enough play with the size of the bolt holes that you could put the bolts through the toilet and tank and tighten everything down and it would still be watertight. So I order yet another tank (from that cheap toilet tank lids place, this time - they had a slightly used one in stock), I received it (uncracked! yay!), was able to move the innards from my ST416M into the ST412M tank, attached it to the toilet (BTW, put your tank bolts on the toilet before you install it on the floor - learned the hard way on that one), got it tightened down, and everything works. I even used the original tank lid from the ST416M tank, with the buttons already installed, and put it on top of the ST412M tank - perfect fit. So everything is now all installed and working perfectly.

    TL;DR - Yes, you can use an ST412M tank to replace an ST416M tank, as long as you switch out the innards (fill and flush) from the inside. (And install your tank bolts on the toilet before you attach the toilet to the floor.)
     

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  4. Terry

    Terry Administrator Staff Member

    Joined:
    Aug 17, 2004
    Occupation:
    Plumber
    Location:
    Bothell, Washington
    Brian,
    Thanks for the update on this. It will help others for sure.
     
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