Toilet and its replacement losing water

In My Humble Opinion
1

What would cause a toilet and its replacement to lose water in the bowl?

My dad had a toilet that needed the arm mechanism replaced in the tank so he called a plumber to make the fix. The very next day the bowl water level would empty within a few hours after a flush. This problem was not happening before the plumber visit.

The plumber told him the toilet bowl had a leak which caused the water to drain out (there’s no puddles so this is all internal). The plumber suggested he buy a new toilet which he did.

The plumber installed the new toilet and immediately my dad noticed again after a few hours the bowl water level emptied. The plumber was mystified but did check the air vents at my dad’s request to see if that would help, it didn’t.

Now the plumber is suggesting he buy yet another toilet.

I don’t know anything about the inner workings of toilets but having two different toilets with leaks sounds a bit far fetched. Is there anything else that could be causing this problem?

2

The drain pipe for a toilet (and all the drains in your house) also have an air hose that goes to the roof. That’s to allow the water to drain smoothly by sucking in air from the top rather than having it bubble up from the bottom. It’s the same principle as when you pour water out of a jug. If you just pour it out, the water glubs out the spout. But if you cut a hole in the top, the water flows out smoothly.

I’m not a plumber, but I’m guessing there’s some weirdness in the air pipes such that water flowing down one pipe is creating suction in the pipe which goes to your toilet. So when water drains out of one part of the house (shower, washer, etc), it’s creating suction that’s pulling the water of of the toilet bowl. This might happen because other air pipe is clogged.

If you have any experience with a bong, it’s sort of the same principle. Lowered air pressure in the toilet vent is sucking bowl water over the hump in the toilet drain and it’s draining out.

You may be able to figure this out yourself. If no one is in the house, does the bowl drain? If not, then it’s likely because some other drain is sucking the water out. Try to check the bowl after different water usages (shower, dishwasher, etc). and see when the bowl lowers.

3

Seems to me the most likely point of failure to cause a toilet to lose water if there’s no puddles is a failing flapper valve. 2 toilets, though? Sounds more to me like there’s a plumber who wants a new inboard/outboard motor on his boat.

4

I’m with Ranger Jeff. A flapper valve you can do yourself.

5

I agree that the flapper valve in the tank is the most common leak point in a toilet, but I’m not sure that would be the case here. If the tank is leaking, it will leak into the bowl. I’m not sure exactly how a tank leak could empty the bowl. Maybe if it’s leaking a lot, eventually enough water will get into the bowl to cause the water to reach the point at which it siphons out like in a typical flush.

One way to test for a leaking tank is to put food dye in the tank. If you see color in the bowl, then the tank flapper is leaking.

6

If the vent is clogged then a sewer system can suck the water out of the bowl. I imagine it could happen with a septic tank that rapidly drains also. But either way the vents would have to be clogged.

7

FWIW, when the wind is blowing hard out of the south, the water level in the bowl of one and only one toilet in my house will drop. So yes, it can be caused low pressure in the vent tube. No idea why it would start happening out of the blue though, unless some other plumbing work was being done.

8

I would not discount the possibility of two faulty units in a row, but I would still set up cameras to watch the toilet.

9

:confused: That can’t possibly be legal. Toilets get used. Recording people using the toilet must violate an assortment of privacy and anti-peeping laws.

If you prevent anyone from using the toilet, then sure, record away. But that wasn’t said.

10

How would filming the water level in the toilet bowl in one’s own home violated any laws? And why would you assume the situation is anything but that?

11

One other thing to check is to see how level the toilet is, especially front-to-back. If it was tilted slightly back, I could see it being a bit easier for the water to be pulled out of the bowl and into the drain.

You should also try to check that the toilet isn’t leaking into the floor. Even if you can’t see puddles, that doesn’t mean it’s not leaking underneath the floor. Go to the floor/basement below and make sure you don’t see any water leaking through.

12

True. Actually there is a pretty easy way to see if the flapper valve has a good seal or not: Vaseline.

When the tank is empty, coat the rim of the top of the pipe that your flapper valve seats against with a thick coating of Vaseline. Then coat the entire under rim of the flapper valve (where it seats with the pipe) with a thick coating of Vaseline.
Let the valve drop into place naturally with gravity only and then fill the tank with water. Then flush.

You shouldn’t hear any water trickling sound once the tank is full. If the problem is with the flapper valve, the tank shouldn’t empty.

13

Does your dad have a dog?
(I can’t believe it has taken 13 posts to ask this)

14

I’ve changed flappers before to fix the problem where water was leaking into the bowl but this type of leak never caused the bowl water level to drop (actually the level stayed the same even though there was extra water leaking into the bowl).

Either the plumber said this or my dad misinterpreted but I’m under the impression the bowl actually has the leak, not the tank. An internal bowl leak, if that’s possible, where there is no viewable puddle but the water drains from the bowl down into the pipe.

From what was said here I’m going to have my dad flush the toilet to fill it then use the shower, the other toilet, washer, sinks, etc. to see if any of them might be affecting this particular toilet.

15

Good one - the plumber asked this too. He does have a dog but it’s small and doesn’t drink out of the toilet. As far as we know… Maybe this is why someone suggested filming the toilet.

16

Did you try unplugging it for 30 seconds and plugging it back in?

17

Try using a plunger on other toilets and sinks, while someone watches the toilet bowl. If there is a vent problem that is causing water to be sucked out, the plunging should rile up the toilet water.

18

Please update us with the results. I always enjoy learning how mysteries turned out.

19

I am no expert, but have redone the different aspects of the toilets in the house.

Toilets have a certain “equilibrium”. That is if you notice, you cannot fill a normally working toilet to the rim of the bowl. Adding water to the bowl will always cause it to act like it is flushing.

It could be possible that the toilet is leaking from the tank into the bowl slowly and that over time it builds up and “flushes”, but then I would expect it to slowly rise again. You also generally can hear the water leaking from the tank to the bowl.

The flapper valve leaking (IME) generally is heard as running water and seldom empties the bowl (as it is maintaining a slow state of equilibrium).

The fact that two different toilets are doing this at the same outlet would seem to indicate (as others have suggested) that there is an external problem.

Does the toilet flush normally and refill normally?

When the plumber replaced the arm mechanism, was just the arm replaced? the entire flushing mechanism? was the tank removed?

When the new toilet was installed was everything replaced? Including the wax ring under the toilet?

One thing I did not know is some plumbing companies (I am sure this depends on the requirements of plumbers in the area) do not always send out fully trained plumbers. My BIL started working at a plumbing company and had very little training and if he started a job and had to go back, he did not get paid extra and if another plumber had to be sent to fix his mistake, the other plumber got paid and he did not. My point is, if they sent out a rookie because it was just replacing the flushing mechanism, he quite possibly knows nothing about “difficult” plumbing situations and could just be guessing at the solution and figures that saying replace the toilet is the easy fix. Then when that did not work, he does not have anything else to offer but do it again.

Could a bad seal on the wax ring cause the bowl to drain (ie letting air escape due to a faulty ring)?

In looking online, one place had 4 reasons, 1 was a leak (not likely since the first toilet was working fine and the second one was new), 2 fill valve not working properly, but you said it filled fine, just did not stay there, so this is likely not the issue. 3 something caught in the trap and causing a wicking effect, but since the toilet was replaced, again this seems unlikely. leaving the 4th reason a clogged sewer vent pipe.

I assume this is not occurring at any other toilets and there are no strange sounds in the pipes.

So from this I would have to go with the blocked sewer pipe.

20

Blocked sewer VENT pipe. It’s an important distinction.