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Thread: Converting from gravity to tank toilet

  1. #1

    Default Converting from gravity to tank toilet

    I live in a NYC co-op apartment, and I find, if during the day while I'm at work, they turn the bldg water off, when I get home the toilet is flushing, i.e. the water is swirling and swirling, sometimes actually spraying outside the bowl. So far it hasn't caused a problem for the resident below me, but I'm concerned that should something like that happen in the future, while I'm out of town, there could be a problem.
    I was told by the Super, that the only way to prevent this is to convert to a tank toilet. Is this true? If so, is there anything vastly different between a gravity flush toilet and a tank toilet installation? For instance, do I have to have a plumber go into the wall and change any type of pipes, etc.? Will I have to install all new pipes? Or will the installer be able to work with the pipe I now have coming out of the wall?



    Thank you for your expert opinions and advice. I'm am a total novice at any kind of home renovation.

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    Yes, you'd have to tear up the wall and replace and move the water supply to use a tank type toilet. If you measure from the finished wall to the bolts holding the toilet down, that will give you the rough-in dimmension. If it is 12", that's fairly common, and would support most toilets.

    While I've used that kind of valve as a consumer, I've not torn one apart or service one. I'd call the manufacturer - it may be that your valve just needs servicing, or possibly just replacement with a newer style. It should not just run. Now, when the water is off, then turned back on, it can dislodge all sorts of crud, and that could be caught in the mechanism preventing it from closing, but I'm not sure why it turns itself on in the first place. See what the pros have to say...
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3

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    Thank you for your prompt reply. I was afraid that tearing up the wall would be necessary. Darn.
    I have noticed that if the toilet is flushed AFTER the water is turned off, but we as residents don't know it was turned off (such as in an building emergency situation) , is when the swirling happens. In other words, the pipes apparently still have enough water in them that it isn't obvious that the water has been turned off, so it flushes normally. However, in this last case, there was a pipe that burst in the basement. The toilet was last flushed at 8AM, but the water wasn't turned off until 9:30AM, so I'm at a complete loss as to the reason this time.
    Perhaps the answer is to lower the flush power or shut the cold water valve a bit? Maybe completely when we go away for more than a day or two?

  4. #4
    Master Plumber Redwood's Avatar
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    The problem is that your flushometer valve could probably be in need if servicing, in many cases this will fix the problem. Valve specific repair kits are available. The labeled parts #7, #13, & #16, in the generic diagram below should all be replaced to ensure proper operation. The Parts on the upper right side above the vacuum breaker label are the stop/check valve. This is not normally replaced as it is the point where the flushometer valve is isolated for servicing. A screwdriver is usually the tool required to shut the stop.check valve off.



    There is also a possibility that these parts will not fix your specific problem. The flushometer if flushed while the water is off will cycle 1 time when water pressure is restored. If the water supply for your building is inadequate to support the volume of all these flushometers triggering at once some of the flushometers will continue to run. If this is the case a plan to resolve it would be the installation of more valves to isolate smaller areas of the building so that pressure drops do not occurr. This would be a good idea anyhow as it is always a good idea to have as few people as possible affected by a plumbing emergency. Usually all that is required to restore the valve to proper operation while it is running as you describe is to turn it off at the stop/check valve and turn it back on.

    The theory of operation of this valve is a little difficult to grasp but essentially water pressure is built up in the area under the #1 & #2 caps above the #7 diaphragm and relief valve in the center of the diaphragm by water that flows through an orfice in the diaphragm. This holds the #7 diaphragm and relief valve down against the sectioned valve body. The outer ring of that valve body is the incoming water supply and the inner ring is the water that is discharged into the bowl or urinal below the valve. The diaphram against the partition between the inner and outer ring is what shuts the valve off. The downward pressure is greater than the incoming water supply because of the hydraulic principle where the larger dia. cylinder under the #1 & #2 cap is larger than the area of the ring where the incoming water supply is located.

    When you press the handle there is a plunger that pushes on the lower stem of the mushroom shaped relief valve which is in the center of the #7 diaphragm and relief valve pictured above. This tipping allows the pressure built up under the #1 & #2 caps to run down the tube of the #7 Diaphragm and relief valve into the bowl or urinal below. This release of the pressure allows the #7 diaphragm to spring upward and opens the flow of water into the bowl or, urinal below. The water then flows through the orfice until the valve closes again when the pressure has built up under the # 1 & #2 cap.

    In your case with a low water supply pressure there may not be enough pressure under the diaphragm to flow water through the orfice. The water going through the orfice is caused by a backpressure of the water flowing down into the bowl or urinal below. If the flow is not high enough to generate this backpressure water will not flow through the orfice.

    If the orfice is blocked by scale or dirt water will also not go through the orfice.

    Did you get that explaination? Probably not but maybe the super will!
    In any case I'd try to get the existing flushometer operating before making major changes.

  5. #5
    Retired Defense Industry Engineer jadnashua's Avatar
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    You might be able to find a different brand flush valve that would fit what you have. The internals would likely be different, and may not experience that problem.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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