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Why do you need a side opening of the toilet bowl tank: plumbing answer

Not everyone knows why you need a side opening of the tank. This design element is not on every model. Around the purpose of this hole are several myths that are not true. I will tell you why this window was added to the design, I will analyze the incorrect hypotheses about its purpose and explain how it should be used, and how - it is impossible.

Side hole in the toilet bowl

Hole purpose: plumbing answer

The question about the extra hole in the tank I was asked by a little nephew. I used to connect the toilet myself several times myself, but I couldn’t immediately answer why they were doing this window. The question was all the more complicated because on some tank models it is, and on some it is missing.

First I went over several versions:

  • The window does not allow the tank to overflow.
  • Through the hole on the side air enters, equalizing the pressure at the time of draining the water.
  • This is a purely decorative element that is needed to install a beautiful stub.

However, these versions did not seem convincing to me or my nephew. Indeed, it is unreasonable to make decoration on the side where few people see it. The version that the window plays the role of protection against overflow also does not hold water: after all, water would pour out of it onto the floor, just as it would pour over the edge of the tank.

The second version seemed somewhat more convincing. Indeed, when draining a large volume of water in the tank, the pressure should drop sharply, which will prevent the water from going out. Air from the room will be sucked into the side window, which will compensate for the pressure drop and drain the water without interference. However, upon closer inspection, this version also disappeared: after all, tanks without a hole work no worse than models that are equipped with it.

In search of an answer, I turned to the forum of plumbing professionals. The answer was simple and clear: two holes made on the left and on the right allow you to connect the tank to the water supply in tight toilet rooms. If the hole were made only on one side, there would be a risk that it would not be possible to supply water from a pipe placed on the other side of the tank.

After connecting the supply to one hole, the second remains unoccupied. It is closed with a decorative cap or left open. That’s the whole secret!

End cap on the toilet bowl

Which tanks have an additional side window?

The received answer turned out to be simple and clear, it completely arranged for my nephew, and it seemed to me exhaustive. To completely close this question for myself, I studied several more publications and pages of specialized forums.

First of all, familiarity with the variety of models of modern toilets showed that not all compact tank models actually have an additional window. Its availability depends on the type of water connection:

  • The traditional type involves the supply of water from the side. This design was first developed in separate toilets, in which a drain tank was placed on the wall, above the seat. With lateral supply, it is important on which side the water pipe is located.
  • A more modern design involves the introduction of water from the bottom of the tank. In this case, there is no need to make symmetrical windows for water supply: the distance between them is small, and even if the hole is located on the opposite side of the pipe, the hose easily reaches it.

Thus, an additional lateral hole is an attribute of models in which water is introduced from the side.

How not to flood the neighbors: adjust the fittings correctly

The hole on the tank looks like a dangerous structural element: if the water level rises above, the excess will spill onto the floor. With such an accident, you can even flood the neighbors. However, having studied the design of the fittings in my tank, I realized that such an outcome is unlikely.

Two mechanisms serve as protection against the flood:

  • A tap with a float through which water enters the tank. When the level rises too high, a light plastic cup will pop up and pull the bar on which it is attached. The other end of the rod will act on the tap and block the water.
  • Overflow pipe. Its height is adjusted so that the upper edge is below the hole, but above the water level at which the float cuts it off. If the float valve fails and water continues to flow into the tank, its surface will rise above the neck of the overflow pipe. After that, all excess water will go into the drain of the tank and will be discharged into the sewer, and not onto the floor.

To make sure that water does not pour out of the toilet tank, place a dry newspaper under it. Each drop will be visible on paper. Even if drops rarely fall, a leak can be noticed by the deformations of wet and then dried paper.

If you find that water has seeped from under the plug of the sub window, check that the float valve is working. This is easy to do: remove the tank cap and lower the float by hand. Water should come from the tap. Then raise the float and make sure that the water has stopped flowing.

You can adjust the position of the float by shortening or lengthening the rod on which it is attached. For example, I decided to shorten it a little, in order to avoid water leakage with a guarantee. To do this, on plastic structures, there are toothed bars with clamps. It is enough to bend the metal wire slightly.

Washing machine connection

Can the washing machine drain be connected to the side window?

Another interesting idea that I met on the forum while I was looking for the answer to my nephew’s question is to connect the drain of the washing machine to an additional window. Technically, this is easy to do: insert the hose into the tank and fix it with a rubber sealant or sealant. The idea promises two advantages:

  • Water saving. This effect is achieved due to the possibility of using the drain of the machine repeatedly for flushing in the toilet.
  • Simple and clean wastewater disposal. When connected to the tank, the hose is fixed, and there is no risk that it will pop out.

However, upon closer examination, this tempting idea has several drawbacks. First of all, at the time of draining the water with a machine, the tank will already be full. This means that the drains will create an excess volume that either goes into the overflow pipe, or even spills through the top to the floor. Of course, you can drain the tank before washing and block the flow of water from the water supply, but this complicates the scheme.

In addition, the wastewater from the machine will contain powder residues, dirt, possibly thread particles and other garbage. All of these contaminants can clog drain valves, resulting in incorrect operation. Therefore, in my opinion, it is better to abandon the implementation of this idea.

So, finding the answer to my nephew’s question helped me to better understand the principle of the drain tank and take a fresh look at the usual plumbing device. I hope that this material seems interesting to you too!

Author: Yuri Mikhailovich

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  1. Vitaliy
    09/02/2019 at 12:13 Reply

    Unbelievable! These holes are for the choice of installing a crane with a float on the right or left, depending on which side is more convenient! And millions of people did not know! But actually, looking at the installed tank, and noticing the complete symmetry of the holes, only a moron can not guess.

  2. Nikolay
    09/02/2019 at 13:44 Reply

    Interestingly, I am the only one so “smart” that I know this since childhood because my father told me this, to whom my grandfather told me in childhood ...
    By the way, on cast-iron tanks there were also 2 recesses under the valve

  3. Tinplate
    09/02/2019 at 14:08 Reply

    I'm in shock, invented toilet paper (maybe someone does not know)

  4. Alanian
    09/02/2019 at 20:04 Reply

    I do not need a monument in life. just say thank you

  5. Alanian
    09/02/2019 at 20:17 Reply

    I did not know what it was intended for and adapted a drain outlet from the washer into this hole

    • The serpent
      09/07/2019 at 02:27

      Plumbers anathema will betray you !!! I adapted the drain from the washer !!! )))) well done!!! Saving water)))

  6. Alexander
    09/03/2019 at 11:08 Reply

    In addition to connecting water to one of the holes, a flush handle with side fittings was installed.

  7. Fima
    09/03/2019 at 21:19 Reply

    author, I’ll tell you the topic, why the elevator in the house?

  8. Gleb
    09/04/2019 at 18:49 Reply

    I wonder why the windows on the windows.

  9. Gregory
    09/05/2019 at 13:18 Reply

    In short, the kulibin, water was connected to one hole, and the drain mechanism to the second, before it was on its side. Only then did the upper lever (button) appear for draining.

  10. Vova
    09/06/2019 at 08:31 Reply

    and also through it you can charge flavoring tablets

  11. Sergey
    09/06/2019 at 12:42 Reply

    I was killed by the beginning, “I myself installed toilet bowls many times,” how can I do something without knowing the subject?

    • Lelik
      11/23/2019 at 22:35

      I killed the heading of the article and further in the text: “In search of an answer, I turned to the forum of plumbing professionals.” This is from the section: “I advise everyone to do this, I don’t know why, but my mother does it.”

  12. Dima
    09.09.2019 at 20:58 Reply

    This is about an additional hole in the tank to breed such a discussion! And if the nephew asks where the children come from? You see, dear tribe, women have an extra hole here ...

  13. Dima
    09.09.2019 at 20:52 Reply

    There you can also +18

  14. Alex
    09.09.2019 at 21:45 Reply

    Awesome discovery! Extraordinary intelligence and the power of engineering.
    On the plumbers website of course.
    And the author had to make a written request to the manufacturer.
    And then they will make holes, but why - a secret. Inhumans.

  15. Yuri
    09/10/2019 at 12:39 Reply

    And the article and comments of some sketch ... you burn of course

  16. Vadim
    09/25/2019 at 08:34 Reply

    The author has amused!

  17. Yuri Mikhailovich
    11/01/2019 at 16:16 Reply

    I used to install toilet bowls many times, but I never thought about why I need a tank. He takes a place that is not enough in the toilet, but does not bring any benefit. But I began to study this issue and realized that I needed a tank to put a roll of toilet paper and an air freshener on it. You can also put a book / magazine on it for reading in the outhouse. A convenient thing turns out. But that’s not all, because for some reason it is connected to some pipes. I began to study why they were doing this and realized that it was possible to drain the drain from the washing machine through a hole in the side. I plan to find out why the toilet itself is needed, otherwise it is inconvenient to wash in it, there is not enough space and you constantly slip into the drain

  18. Alex
    11/04/2019 at 19:46 Reply

    The author also tell why the hole in the ass. And no one knows, everyone wonders ...

  19. Reader
    11/07/2019 at 08:46 Reply

    Neighing from the heart.

  20. Pavel
    11/15/2019 at 23:52 Reply

    Give Dude Nobilevka. And then the whole world lived and the factories riveted two openings on the tank under the valve and did not know why.

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