Hi Everyone,

First time poster here, and I'm turning to you all with the hopes someone can help me; at least get some brainstorming going. I've had numerous plumbers visit and none have been able to assist. Rather than continue to call plumbers and sink more money into this (which I would gladly do if I had some degree of certainty the next plumber I hired would be able to diagnose my issue), I figured I would see if the expertise on this forum can point me in the right direction.

Here are the key facts of my situation that I am certain of:

We moved into a new home about 5 years ago. We have 4 toilets in the house - 1 in the basement; 1 on the main floor, and 2 on the second floor. The normal resting water level on all 4 toilets has gone down since moving in. This started maybe 2.5 to 3 years after moving in (so has been ongoing for quite awhile, despite attempts to have plumbers come and try to diagnose). When we flush, the water level rises in the bowl as you'd expect, then drops at a normal rate as it balances with the trap as you would expect. However, after this, the water extremely slowly continues to drop. In the dead of the night, if you put your ear close to it, you can hear an extremely faint trickle. This happens to a point and then it stops. It does this to the same point each and every time, so there is consistency. There is still water covering the hole and everything, but again, the "new" resting water level is much lower than what the normal resting water level was since we moved in. It seems like there is some sort of siphoning happening sucking additional water over the weir that shouldn't be going over.

Our toilets are on at least 2 different vent stacks, so I don't believe it is a blocked vent, as I'd assume only the toilets on the blocked/partially blocked vent stacks would be impacted, not all 4 toilets.

Further, unless I'm going crazy, this issue only started with the 2 toilets on our second floor. Then seemed to notice it with the 1 toilet on our main floor, but to a lesser extent (the "new" resting level still being different from when we first moved in, but higher than the "new" water resting level for the 2 toilets on the second floor). And initially no issue was noticed with this for the toilet in the basement.

Now, it appears as though this issue is just as bad for the 1 toilet on our main floor as for the 2 toilets on our second floor. Further, it now appears that the basement toilet is being impacted; however, the extremely slow water recession seems to take even longer than the other toilets.

I have brought in someone to do a camera inspection on 1 of the 2 toilets on the second floor, and the basement toilet. Nothing out of the ordinary was discovered; however, we couldn't run the camera all the way to the main sewer line from the basement toilet to check if there was a partial clog way down our line or possibly the main sewer line. We did get a fair distance, though, and again, nothing unusual could be seen. For at least these 2 toilets, lines looked clean, indications slope was fine etc.

In terms of slow or sluggish drainage around the house - at times when running our master bedroom sink (same bathroom as 1 of the toilets on the second floor), bubbles start to form at the sink drain after 10-20 seconds, and then the sink starts to fill up. When I turn the faucet off, the water drains slow until almost fully drained and then there is a noticeable "glug" as if a bubble/air pocket is popping and the small amount of water left then quickly drains. Sometimes I can turn the faucet back on right after full blast and just constant, steady, fast draining as you would expect. Literally right after this "bubbling back up" happens. This never was the case when we first moved in. I want to say this started around the same time as the toilet situation above, but I'm not entirely sure on that. For clarity, there are no signs of any sort of debri backing up or what have you; it is just this bubbling. I have a video I could try and post to illustrate. It is almost like some sort of air pocket is being creates or at times exists and not letting the water drain freely until it pops. It seems totally random when this is happening and when it is not - i.e. it doesn't seem tied to when other fixtures are in use, not in use, etc.

This is happening in the other spare bathroom sink also on our second floor, but only on very rare occasion.

We have not camera inspected these sinks; however, I don't think there is a clog or I assume this would be happening 100% of the time we turn on the faucets and that we wouldn't get that pop/glug when the water is almost fully drained with the small amount of remaining water speeding up back to normal drain speed.

I have no clue if this sink issue is related to whatever is going on with our toilets.

The other thing to note, which again I have no idea if this is tied to these issues or just coincidental - around the time this started happening, we had our ducts cleaned. The day they were cleaned is was an extremely cold day, -25 to -30 degree Fahrenheit. This created a crazy negative pressure in our house to the point where, when the front door was opened during this process, if you just let it would go it would slam shut with a lot of force by itself.

In addition to hiring plumbers, I've spent hours upon hours Googling trying to educate myself on what could be causing this toilet issue/sink issue.

Could we have a vent blocked, despite the toilets being on different vents?

Does this sound like siphonage?

Could this just be crappy toilets (all of which are the same) wearing out or something?

Could we have some sort of blockage further down than the camera got?

Is there any way the duct cleaning negative air pressure has caused damage/screwed something up with our plumbing?

Could this be some sort of stack effect with respect to hour air is being distributed in our house with certain vents closed/open (we do have a bonus room 3rd floor, but no toilets up there, so it is a fairly tall house)?

Could this be a water pressure issue?

I have honestly spent so much time on this and am desperate as can be to find out what is going on. I'm tempted to just replace all the toilets, but feel that isn't needed and would just be even more of a waste of money.

Any thoughts anyone can offer would be very much appreciated. I'll try anything. Also, if I need to provide additional information or clarify anything, please do ask.

Thank you to this community in advance! If there is anyone near Edmonton, Alberta Canada on this forum that knows how to fix this, I will pay you extremely good money!

You can remove a toilet and set it on bricks/blocks, so a drain pan can be slid under it. Pour water in the bowl to the "normal" level and see if it level drops on it's own.



Edited 1 times.

Thanks, Steve. I wouldn’t be able to do this myself and am hesitant to call more plumbers in without some idea of what this might be.

I also should add that, even if I just add a small amount of water to the bowl with a cup to bring the water level up, the water level still seems to go down to a lower than normal resting level without flushing.

Have ALL the vents inspected/cleared from the roof.

==============================================

"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638



Edited 1 times.

I have managed to get to 2 of 3 vents, blasting a garden hose down them. The last one is difficult to reach without a massive ladder, which I do not own and the plumbers I had come out also did not.

Do you think even just one blocked vent could be causing this?

One vent blocked will not cause this to happen
A partial blockage will cause this to happen in the 1st floor toilets
Have you had the sewer main cabled and video inspected
Also do any of the other lav drains have the slow/bubbling issue



Edited 1 times.

I have not had the sewer main camera inspected. Definitely open to doing so; however, would like to rule out other possibilities first.

Regarding the bubbling, the two sinks in our master ensuite on the second floor do this, and also a sink in the spare bathroom on the second floor does this but not near as often. The master ensuites sinks do this at least once a day, often multiple times but not every time. The sink in the spare bathroom on the second floor will do this every now and then but definitely not every day. Why would this bubbling be so inconsistent in our master ensuite if this is some sort of blockage? Would you expect it to happen each and every time?

Thanks to everyone who has responded so far.



Edited 1 times.

does the blowing wind affect this situation?

another thought.
i know its wasteful but leave a faucet dribbling all knight.
see what happens?
check the toilets every couple hours.



Edited 1 times.

The blowing wind does not affect the situation, given we had windy days before this started happening 2 years ago. But even now whether windy or not it doesn’t seem to matter. On windy days, I can see movement in the water.

What would letting the faucet dribble do? what should I check for?

have a read about oscillation.

[www.google.com]

the dribling water is just a guess.
if there is a partial stoppage in the sewer main and it is creating a suction that is causing your problem, then perhaps trickling a little water will satisfy the suction and the toilets will not syphon ????



Edited 1 times.

? Were the 'plumbers' you have called licensed, insured, and BONDED ?

If not, how much did you save ?


Your main sewer line needs to be 'videoed' and then cleared or repaired as required.

At this point you need to work backwards from the main drain.

==============================================

"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638



Edited 1 times.

Yes, all licensed plumbers - I didn't hire cheap plumbers; all reputable and so no money saved.

Except for posts I've seen on this forum, it just seems many plumbers are lacking some of the science behind these types of issues, and consequently, just give me blank stares when trying to discuss with them.

So am I correct in that something definitely seems off, and that this is not just me being crazy?

Any possibility that these issues could be connected to the immense negative pressure in our house caused by the duct cleaning? Or is that a red herring/coincidental?

If this seems to be an issue and not just me being crazy, my next steps seem to be to start with the main sewer and work backwards. Is it worth confirming no vents clogged at all first?



Edited 1 times.

vents are the last possibility.

have a sewer camera run down the main.

So, it clearly seems there is an issue with pressure differentials between your local house sewer system and the atmospheric pressure in the house. Only that would account for all four toilets going down consistently.
Bern's comment about cleaning out the vents is because he is guessing the vents are clogged. This is a distinct possibility - the vents _should_ equalize the pressure between the internal sewers in the house and the atmospheric pressure. The way your sewer drains into the main sewer _might_ be such that water (from other houses) running in the main drain past where your drain the main, can reduce the pressure in your drain (Bernoulli effect). If the vents at your house are clogged, then the pressure will not equalize, and the toilets may drain slightly. Also, if the vents are clogged, it might account for the behaviour you are seeing when draining your sinks: if you fill a sink with water and then pull the plug, the water draining into the drains can create a slightly high pressure in the air in the drain pipes. When the water has partially or completely drained, that increased pressure can cause a bubble-back through the trap. Even clogged drains can cause this.

If the vents on your house are not clogged, Packy's question is again related to Bernoulli effect: wind blowing past the opening of a vent can produce a low pressure in the vent (Bernoulli effect), so if your vent openings are situated where there is always wind, this could be the issues. You say that wind levels are irrelevant, so perhaps not. But perhaps some opening is beside a wall of your house where there is a constant wind? Small possibility.

Is your house particularly well sealed, so that pressure inside the house is different from the outside world? Not sure how you could consistently get the house pressure consistently _above_ outside pressure, but have a think about the systems in your house.

Perhaps there is some secondary trap elsewhere in the drains that is causing a "pressure" trap? Not likely, but... Or maybe just a clog?

I have a house in Toronto that I rent out. When it sits vacant for a while, the toilets always drain a bit, from temporary pressure differentials. Nothing really that can be done about it, but so long as the toilets are being used and refreshed, it's not a big deal.

Fundamentally though, there is _some_ issue with the venting of the sewers in your house preventing quick pressure equalization.



Edited 2 times.

There is another possible cause of siphoning toilets, that I will put here just in case other users read this. It is almost certainly not your case here, because all four of your toilets are behaving the same.

If you have kids and you flush down wipes, it is possible for a wipe to get caught and be hanging over the back of the trap. The wipes never degrade and can act as siphons. I had this happen once to one of my toilets, was a mystery for a couple of years until I replaced the toilet, but that is an uncommon occurrence, and highly unlikely to happen to four toilets at once.

DIYer here and not a plumber so my comments could be way off.

You mentioned you have two different vent stacks. Four toilets, one in basement one in main floor and two in the second floor. Are these two vent stack independently penetrating the roof? I ask because sometimes the vent from the basement reconnects to the one on the first floor which connects to the one on the second floor. Do you know if they are all tied together?

Further, do you have any AAV in the house?

Third, when you say the water level goes down, and it goes down in every toilet, but the amount varies. This may seem far fetched, but is it possible this can be caused by evaporation? My swimming pool drops 1/4" a day due to evaporation in a 90% humidity south Florida. Are you running dehumidifiers in the house?

Florida swimming pools are in hot sun. He is in Canada (though we do get hot days), and toilets are indoors. lol.

Yes pools are under the hot sun, but as the humidity increases, at say 99%, the air is saturated and there is no more evaporation. We are dealing with very high humidity that slows evaporation, and despite a daily rain storm that adds water to the pool we still end up with 1/4" of loss a day. It would be significantly more in a dry place like Las Vegas. That's why I asked if he may be running dehumidifiers that may be pulling water from the air.

Thanks for the detailed response!

Our home should be fairly tightly sealed and I do believe our house is slightly at constant negative pressure. Not a crazy amount, but slightly. Perhaps I should try and increase air intake on our hrv? During the summer the hrv doesn’t run (to avoid just pulling in hot, humid air) and this issue still exists. That’s the only reason I don’t think it’s an hrv adjustment. I’m not sure what other system could be causing a negative pressure? Maybe I need to balance out my actual vents?

Definitely not evaporation - this is happening within an hour or so, faster on the second floor than the main floor. And faster on the main floor relative to the basement. Everything is worse higher up and gets better as you go down floors.

There are actually 3 vents I can see sticking out of my house, so don’t believe they are tied together.

No AAVs I don’t believe.

To clarify with the sinks - if I fill a sink up and open the drain, I don’t get the slowed water drain near the end. It drains nice and fast as expected and no pop/belch at the end. This is also why I don’t think it’s a clog in the drain. This water starting to “back up” with bubbles, slow drain, then belch noise and fast drain only happens when the drain is open and water running on full blast, and like I said, not every time. So I guess the question is, what would cause this to happen but not when I’m draining a full sink?

Based on this new information, any other recommendations? Or should I try and bring out an experienced plumber for a full day to check vents, camera main sewer, and as much else as possible?



Edited 1 times.

RE - Lav sinks draining slow -

Remove the stopper, run water and if still does not drain, stoppage is further down the pipe. If it does not back up etc., then it is just the design of the stopper and how the water is hitting it.


Can also try running the water with stopper in place like normal and use your hand to direct water away from stopper. If it drains fine, it is again just design of stopper and how water is hitting it.

Can also try running the water at different flow rates and see what happens.

Some stoppers are adjustable for height. If the one you have is, trying raising it to allow more water to enter drain.

Post is pretty long and maybe I missed something and this has already been covered......

If you really feel it’s negative pressure caused by your duct system. Shut off the heat And then flush the toilets leave the heat off for a couple hours. See if this scenario is still the same.

The negative pressure scenario is highly unlikely But technically Could happen

Yeah I think I've ruled out negative pressure, bsipps, thanks!

Curly - it happens without the stopper but very rarely. Perhaps some sort of build up.

I will likely try and bring a plumber in to just camera everything starting with the main, and also look at the vents. Not sure I have another choice at this point.

Thanks all for the responses.



Edited 1 times.

I wouldn't worry about your sink drains. I think the point of Curly's post was, it happens. It's not such unusual behaviour.
The toilet drain issue would be caused by positive (not negative) pressure in the house relative to the pressure in the drains in the house, pushing the water up over the trap. Now, presumably your vents keep the sewer drains at the same pressure as outside the house, but that is not certain.



Edited 1 times.