Toilet Mystery

[N80]

Whenever I have any sort of technical or mechanical issue I know I can come here and you guys will solve it.

I have a toilet mystery.

Background: I have repaired toilets many times. I have replaced toilets. I have installed new toilets and even the entire drain-waste-vent system in my cabin. And yet there are still things I don't understand about toilets.

My problem: 3-4 months ago our previously functioning master bathroom toilet (2nd floor) stopped maintaining the bowl water level. It flushes normally. The bowl fills back up to the normal level. But over 5-10 minutes the water level in the bowl (not the tank) goes down to about 1/4 of the normal level. I see no cracks in the bowl or waste channel. There is no water on the floor. There is no water or stains on the downstairs ceiling below the toilet.

It might be something obvious but I cannot figure this one out. Open to any and all suggestions. Thanks in advance.

 

[Peter 315]

Dogs?

 

[cholland]

is it vented properly? or is something obstructing the vent pipe? I have heard squirrels will sometimes fill vent pipes with acorns.
Poor venting, could create a vacuum and pull water down?

 

[MoKelly]

Other than dogs, there are 2 possible causes that I am aware:

1. Hairline crack in the tank allowing water to escape down the drain. You’d never see this on the floor or in the basement.

2. Clogged air vent. If there is a blocked vent, water drained on the first floor will result in drawing air from 2nd floor fixtures causing the water level in toilet to fall.

MoKelly

 

[MossRoad]

A vent pipe could be blocked or pitched incorrectly.

Or the toilet could have an internal crack in the S bend.

 

[N80]

Dogs? That's thinking out of the box and a good thought! Yes, we do have a dog but that's not it. You can watch the level go down.

Crack? I thought of that but I can't see how that is it. The S pipe on this toilet is visible. No visible cracks. For an internal crack to leak into the drain the crack would have to be in the upper part of the S and communicate with the lower part.

Clogged vent? Possible. However, when I had that problem before on another toilet the toilet would not flush properly because it could not draw air through the vent. This toilet still flushes briskly. Also, the vent on this toilet does not vent any first floor fixtures.

I'm not ruling any of these out except for the dog. The vent is on the roof. I'll have to have someone check it for me. It is nearly three stories high and a steeply pitched roof and I don't go up there. To find some sort of internal crack the toilet would have to be removed. I may do that if the the vent is not the issue. It will be hard to get myself to do that since it is otherwise working properly.

To be honest I'd thought of both of those but couldn't figure out how they could cause this issue. Certainly open to other thoughts or corrections in my reasoning (or lack thereof).

 

[Wagtail]

There could be a partial blockage at the bottom of the waste water pipe where it meets the 'main' pipe.

Due to the drop from the second floor, enough flushed water could be causing a slight suction (enough to claim 1/4 of the 'bowl' level) until the vacuum effect evens out.

 

[kennyd]

As mentioned above several times, I too suspect a vent issue.

 

[MossRoad]

At our current house we have a vent pipe that runs basement to roof. I found it had slipped in its brackets and dropped a couple inches. That allowed water to pool in the bottom of the elbow right below the vent vertical. I had to push it back up to correct pitch, then brace it permanently from the bottom to hold it up, because the brackets were buried in a wall I did not want to tear into. The issues caused by that situation were strange flushing(just didn't look like the normal swoosh), gurgling sink drains, and occasional sewer smell after gurgling events. Took a while to figure out, but visual observation and a level can tell you if pipes are pitched correctly.

 

[fidowanttobe]

Before you go to bed, put a drop of food coloring in whatever water is left in the bowl to see if it is still there in the morning. If it is not, you have a leak.

 

[nybirdman]

If you are on a septic tank system;I would guess the tank is full and need of pumping.

 

[MossRoad]

How to test the toilet for internal leaks in the S.

Requires removing the toilet, placing it on a drip tray, filling the bowl with water, and watching it pour out the bottom. Pretty foolproof, quick and easy way to determine if its the toilet or a vent issue.

Should only take about 10-20 minutes to rule out the toilet this way.

 

[k0ua]

Watching this thread with interest. I don't have a problem, but I am always looking to learn new things. I don't have much experience in these things.

 

[N80]

To address some of the last few posts:

Not sure food coloring would help as the bowl is not refilling from the tank unless it is flushed. I think, maybe incorrectly, that if the bowl was leaking and I put blue food coloring in the water all I would see is less blue water but not diluted blue water.

Not on a septic tank. And importantly, everything else in the house is working fine (I hate to even say that, sure I'm jinxed now). Even the sink and shower in the same bathroom are draining perfectly.

I really don't want to remove the toilet. For me, things that take twenty minutes usually end up taking an hour plus a trip to the hardware store. The question I have is that if the part of the S pipe that holds the water had a crack in it, I should be seeing water on the floor, right? I just don't see any way the the upper part of the S is cracked and leaking into the lower part of the S and thus down the drain. On this toiler the upper and lower parts of the S do not communicate except through the channel. In other words, as far as I can tell they do not share a common wall. The floor of the upper S pipe is not the ceiling of the lower part.

I will go in the attic and see if everything looks okay with the vent pipe from that vantage point. It is hard to see on that part of the roof but from what I can see everything looks okay from the ground.

I don't think a plumber is going to go up on my roof. Where the vent stack comes out is three stories up and steeply pitched. I might have to get a roofer to come out and inspect it.

 

[MossRoad]

To address some of the last few posts:

Not sure food coloring would help as the bowl is not refilling from the tank unless it is flushed. I think, maybe incorrectly, that if the bowl was leaking and I put blue food coloring in the water all I would see is less blue water but not diluted blue water.

Not on a septic tank. And importantly, everything else in the house is working fine (I hate to even say that, sure I'm jinxed now). Even the sink and shower in the same bathroom are draining perfectly.

I really don't want to remove the toilet. For me, things that take twenty minutes usually end up taking an hour plus a trip to the hardware store. The question I have is that if the part of the S pipe that holds the water had a crack in it, I should be seeing water on the floor, right? I just don't see any way the the upper part of the S is cracked and leaking into the lower part of the S and thus down the drain. On this toiler the upper and lower parts of the S do not communicate except through the channel. In other words, as far as I can tell they do not share a common wall. The floor of the upper S pipe is not the ceiling of the lower part.

I will go in the attic and see if everything looks okay with the vent pipe from that vantage point. It is hard to see on that part of the roof but from what I can see everything looks okay from the ground.

I don't think a plumber is going to go up on my roof. Where the vent stack comes out is three stories up and steeply pitched. I might have to get a roofer to come out and inspect it.

Not necessarily. It could be an internal leak. I know it seems unlikely, but hey.... (insert ____ happens joke here).

I'd guess that even with a blocked vent that after you flushed, it would eventually stop sucking water out of the toilet until some other device was flushed.

Maybe try filling the bowl with water slowly up to normal level with a bucket. Make sure no other fixtures are draining and watch the water level. If it drains down, there's probably a leak in the S pipe on the toilet. If it doesn't leak down after 15 minutes, turn on the sink and shower and see of it pulls water out of the toilet. If not, try some other fixtures in the house. Stuff like that. If other fixtures cause the toilet to drain, it's probably a vent problem.

 

[N80]

I’ve done the bucket test. The water level starts going down immediately. Slowly but visibly.

This is with nothing else running or draining.

I guess I am going to have to pull the toilet.

 

[MossRoad]

Bummer.

 

[MossRoad]

My dad always told me to buy 2 wax rings when pulling a toilet, because you'll mess one up putting it back in place. I'm so good at it now I buy 3.

 

[JPRambo]

Have you tried a toilet snake? Maybe something got partially flushed and creating a siphon. I worked in a hospital maintenance department for 19 years found a lot of weird things happen.

 

[MossRoad]

Have you tried a toilet snake? Maybe something got partially flushed and creating a siphon. I worked in a hospital maintenance department for 19 years found a lot of weird things happen.

That's definitely worth a try before pulling the toilet.