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Thread: older toilet and (mismatched) 1.6 GPF tank

  1. #1
    DIY Junior Member rgar98's Avatar
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    Jun 2011
    Miami, FL

    Default older toilet and (mismatched) 1.6 GPF tank


    I replaced a cracked older tank with a smaller 1.6 tank and the toilet only flushes intermittently and fills incompletely. When it fills properly, it flushes. There are no blockages (I used a closet auger); the holes along the rim are cleaned out and the tank fills properly. But, the flush is weak and sometimes nonexistent. If I hold the lever longer than normal it will sometimes help the flush strength.

    To complicate matters, the toilet needs an offset flange, but it doesn't have one now. However, it flushed properly without the offset flange prior to the cracked tank problem.

    Woe is me.

    Last edited by Terry; 06-22-2011 at 04:15 PM.

  2. #2
    Forum Admin, Expert Plumber Terry's Avatar
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    Aug 2004
    Bothell, Washington
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    Installing a 1.6 gallon tank on your old 3.5 or more bowl is like sending your kids to school without breakfast.

    Next time, get the bowl with the tank.

  3. #3
    In the Trades Gary Swart's Avatar
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    Sep 2004
    Yakima WA


    Your comment about the offset flange would indicate that a regular flange would set too close to the wall. If that is the case, there are ways to deal with that problem and still use a regular flange. More details and even a picture or two would help with that. I do think you are in need of a complete toilet. Terry's comment is a good one, I'd add another. Buying a 1.6 gallon tank for a 3.5 toilet is like buying a set of new Ford piston for a Yugo. LOL But, gimmicks not much different than that were what many manufactures tried when the new low flow requirements came in. Mixing old technology with new just didn't work. That's what gave low flow toilets a reputation that low flow toilets would not function right and would constantly clog. Many people still believe that, and sad to say some of the big name manufacturers are still trying to tweak the old technology with limited success. Toto redesigned the entire lower portion of their toilets, but kept the flushing mechanics pretty much the same...simple, cheap, and available. Let us know about how your flange is located, and perhaps we can offer some suggestions.

  4. #4
    Plumber jimbo's Avatar
    Join Date
    Aug 2004
    San Diego


    Your bowl was engineered to need probably 3.5 gallons per flush, if not more,
    So when you give it only 1.6 gallons, it can't really get the siphon action going to pull all the waste out.

  5. #5
    Moderator & Master Plumber hj's Avatar
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    Aug 2004
    Cave Creek, Arizona


    Depending on the toilet's age, it COULD use 6.0 gpf, but regardless it is NOT engineered for a 1.6 gpf tank and there is NOT enough water to flush the bowl properly. In fact, many manufacturers designed their 1.6 gpf tanks so they WOULD NOT attach to the older bowls for just that reason.

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