Sink gurgle when toilet flushes, plumber cant figure it out

I live in a one story manufactured home.

Remodeled half bath but did not change any plumbing just added a new toilet and vanity. The plumbing is identical to the original.

When I flush the new toilet a AS Cadet 3.

I get a gurgle in the 1/2 bath sink and my kitchen sink which is next down the line from the 1/2 bath.

At first I thought it was a vent problem with siphoning, so I put new air admittance valves on. Even got the really expensive 20 dollar a pop ones. nope that did not fix it. Note that when i take the air admittance valves off there is no gurgle. I believe that I don't have an air admittance problem at all. Air is not being drawn in from the sink past the trap. I believe air is being forced past the trap up in to the sink.

So I put water down my roof vents and nothing backed up and then called a plumber.

I am on a septic and unfortunately they did not install a clean out on the septic side. so we started at the end of the house and ran the snake as far as the guy could it went past my house but I don't think all the way to the tank as I think we had too many bends and friction fighting us.

Plumber think there is a blockage from the house to the septic tank.

I can run all water sources in the house at once and no back up at all. I can flush every
other toilet in the house and no gurgle just the one in the half bath.

I already shelled out 325 dollars for the guys to snake etc and he wants to charge another 300 (discounted price) to send a camera down and inspect for a blockage.

So my question is if there was a blockage would it not just cause a slow draining toilet? Why would it gurgle in the sink? The toilet flushes fine it actually drains fast mush faster than the Mansfield that was put in the house when new and the old toilet that I replaced did not cause this issue.

So I'm leaning toward a vent issue as the culprit. The volume of water going down the drain has to push the air somewhere and the roof vents are not adequate enough to evacuate the air so air is being pushed past my two traps. I cant see how a blockage that has no effect on drain time would cause an issue with air blowing past my traps.


My thoughts are to perhaps hand snake my roof vents perhaps water passes through but there is an obstruction not allowing air to move fast enough. Perhaps even putting a shop vac on the vents to see if something has got caught up in the vents.

Any and all help appreciated. I'm an internet educated DIY homeowner looking for help.

AJ

An AAV does nothing for positive pressure in a drainage system. This is one reason they are not recommended for many installations.

cacher_chick said:

An AAV does nothing for positive pressure in a drainage system. This is one reason they are not recommended for many installations.

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cacher_chick thanks for the response and its exactly what is said in my post. i don't think i have an air admittance issue. I have a pressure release issue. i have a vent problem with the stacks that go to the roof. In addition to the AAV i also have a through the roof vent right at this toilet and one past it at the laundry room which is right before the wasteline exits the house.

NCMIIW but shouldn't those two vents be adequate enough to release the air pressure from the toilet water going through the pipe?

AJ

In a properly installed plumbing system, every fixture in the building is vented. It can be plumbed so that the vents are tied together before they exit through the roof, reducing the number of penetrations required. Without seeing how the drains and vents are installed in your house, we could only guess as to the exact source of the problem.

cacher_chick said:

In a properly installed plumbing system, every fixture in the building is vented. It can be plumbed so that the vents are tied together before they exit through the roof, reducing the number of penetrations required. Without seeing how the drains and vents are installed in your house, we could only guess as to the exact source of the problem.

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Yeah i know its hard to diagnose over the net however hypothetically could a newer toilet that sends the water out faster than the previous one cause the issue I am presenting? Basically could the the venting I have either be inadequate or potentially obstructed not allowing the air out and then forcing the air through the p-trap?

The plumber that came to my house did not look at the vents. I said I ran water down but they did not back up. I guess he thought that was enough. In this scenario I guess pressure is better than vacuum as water will just run back down into the p-trap from the drain vs being siphoned out and allowing sewer gas in the house. But I dont like the sound of it. Wish I still had my old toilet to test it with.

AJ

If everything is vented properly and there are no obstructions, things should not gurgle.

hypothetically could a newer toilet that sends the water out faster than the previous one cause the issue I am presenting?

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Yes.

The newer toilets with a 3" flush valve push air and water much more forcefully than before.
If you can extend the vent up through the roof, you should be fine. As you know now, it's not admitting air, it's giving air a place to go. You have a "positive" pressure when the new toilet is flushed.
I see it all the time.

The new wet venting codes were put in practice "before" the advent of the new high performance toilets.
My guess, is that it will take years to convince some of the older plumbers that times have moved on.
Plumbing design must take into account the new performace levels that we are seeing.

Terry said:

Yes.

The newer toilets with a 3" flush valve push air and water much more forcefully than before.
If you can extend the vent up through the roof, you should be fine. As you know now, it's not admitting air, it's giving air a place to go. You have a "positive" pressure when the new toilet is flushed.
I see it all the time.

The new wet venting codes were put in practice "before" the advent of the new high performance toilets.
My guess, is that it will take years to convince some of the older plumbers that times have moved on.
Plumbing design must take into account the new performace levels that we are seeing.

Click to expand...

Ok so im not crazy!!! The plumber who came to the house was convinced I have a drain issue. I let him snake it I guess I know now that its not. I mentioned the vent issue and he was not convinced.

The 1/2 bathroom does have a vent to the roof but the next fixture down the line does not which is the kitchen sink. however about 5 feet from it is the laundry drain that does have a vent. I suppose they just arent big enough to handle the amount of air. For good measure though I will run my shop vac in the vents again and run water down and an auger.

If that does not work I guess I will look for a toilet in the same style that does not have a 3" flush valve.

Terry I want to thank you so much.

You're welcome.

But I would be inclined to keep the toilet and just figure out a solution for the venting. So maybe the sink should have a vent, besides the AAV.
The Cadet has been working well, and most are going in that direction.

Terry let me start over.

The bathroom is wet vented like this. so it has roof vent and an AAV under the sink.



Then the main drain line goes to my kitchen sink which looks like this. There is no vent to the roof.it only has an AAV.



On the other side of the wall on the left of the kitchen is the washing machine which has a vent to the roof which I think is supposed to help vent the kitchen. after the laundry its out to the septic system which was recently pumped.

There is other vents in the house upstream. I guess in a wet vent system they are all supposed to help each other so perhaps one still has an obstruction some where.I know there are rules on distance etc but im no professional. I do understand science and higher pressure will always seek lower pressure to take its place.

I only ran water down the one in the laundry and the 1/2 bath. The kids bath is under a large cedar tree that lets needles out like crazy. perhaps its got some issues. I dont hear gurgling in there but really havent even listened in there. perhaps it may help to clean it out if its got a clog in it.

in worst case not enough venting and I will have to add one which in a case of a manufactured home with no attic space is gonna be a major PITA. I will be on the roof tomorrow and tackle the vents one more time and will let ya know how it all goes down.

ajohansson said:

Terry let me start over.

The bathroom is wet vented like this. so it has roof vent and an AAV under the sink.

Then the main drain line goes to my kitchen sink which looks like this. There is no vent to the roof.it only has an AAV.

On the other side of the wall on the left of the kitchen is the washing machine which has a vent to the roof which I think is supposed to help vent the kitchen. after the laundry its out to the septic system which was recently pumped.

There is other vents in the house upstream. I guess in a wet vent system they are all supposed to help each other so perhaps one still has an obstruction some where.I know there are rules on distance etc but im no professional. I do understand science and higher pressure will always seek lower pressure to take its place.

I only ran water down the one in the laundry and the 1/2 bath. The kids bath is under a large cedar tree that lets needles out like crazy. perhaps its got some issues. I dont hear gurgling in there but really havent even listened in there. perhaps it may help to clean it out if its got a clog in it.

in worst case not enough venting and I will have to add one which in a case of a manufactured home with no attic space is gonna be a major PITA. I will be on the roof tomorrow and tackle the vents one more time and will let ya know how it all goes down.

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Apparently you guys don't work on too many mobile homes. It gurgles because there a sag in the drain line and there's a sag in the drain line because it's ABS and it's hung with mechanics strap every 10 feet or so. Mobile homes are notorious for that problem. Solution, open up the under belly and hang it right. While you're at it, hang it all right.

COmbine a septic system and an AAV, and you CAN get gurgling even if the line is NOT clogged. It may have NOTHING to do with it being a manufactured structure, OR the ABS being hung under the coach.

Tom Sawyer said:

Apparently you guys don't work on too many mobile homes. It gurgles because there a sag in the drain line and there's a sag in the drain line because it's ABS and it's hung with mechanics strap every 10 feet or so. Mobile homes are notorious for that problem. Solution, open up the under belly and hang it right. While you're at it, hang it all right.

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Ok im following with a sag. The sag would cause the water to slow down. I can tell you that I have no problems with drainage as the toilet flows fast but i am going to fill a few 5 buckets with water to day and do the pour test. Can you explain how that would cause air to get pressurized past my trap and blow into the sink instead of out the through the roof vent? Prior toilet had no problem at. Cadet 3 with its 3" drain valve is causing problem.

hj said:

COmbine a septic system and an AAV, and you CAN get gurgling even if the line is NOT clogged. It may have NOTHING to do with it being a manufactured structure, OR the ABS being hung under the coach.

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Thanks for the response. Could you explain a bit further on this. What issue should I be looking for? The how is not solely vented with AAV It is wet vented with 4 separate vents to the roof. One for each bathroom and one for the laundry room.

I really appreciate this forum. at the very least its getting me closer to ruling out certain issues. I do agree with Terry about the large valve pressurizing the drain pipe and that air is getting pushed through the trap not siphoning it out do to vacuum.

Will be home in a few hours and up to the roof I go.

Look at your diagram of the toilet & sink vent. If someone really plumbed the base of the stack with a tee instead of a wye, that alone could contribute to the problem.

As they say, the devil is in the details.

Could ajohansson maybe get a deeper trap to increase the water seal from 2 inches to 4 inches? I am suspecting that might compensate for imperfections elsewhere in the system.

Got to the roof. flowed massive amounts of water down vents. vacuumed vents. everything is running super clear.

cacher_chick said:

Look at your diagram of the toilet & sink vent. If someone really plumbed the base of the stack with a tee instead of a wye, that alone could contribute to the problem.

As they say, the devil is in the details.

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I guess I will have to get under the house and see how they tied the vent in to the main drain. Thats what your referring to correct when you say "Stack". To confirm this is a wet vent system. Everything is exposed under the house its just a 40 foot crawl to go look.

Reach4 said:

Could ajohansson maybe get a deeper trap to increase the water seal from 2 inches to 4 inches? I am suspecting that might compensate for imperfections elsewhere in the system.View attachment 23690

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Ok I confirmed it is pressure thats the issue. First I poured 20 gallons straight down the toilet, i couldnt pour fast enough the cadet just flushed and flushed. I really dont think I have an obstruction or even a sag as it just takes the water down like a champ. Next I took the drain into the p trap off and got a flash light. Ptrap was full of water. I flushed the toilet and the water rose up a 1/2 inch then back down and bubbed which is the gurgle i hear.

Would adding more water via longer trap seal keep the gurgle out? maybe force it out the vent stack to the roof? Is this something I just extend using my previously installed trap or is better find one pre made.

I guess the good thing is that its not vacuum but pressure Im dealing with. I get a small air bubble of sewer gas that comes in which it never smells. the p trap stays full as the air pressure causes the water to rise not siphon out. I suppose its the lesser of two evils.



as always any help appreciated.

A wet vented system works because there is never enough water in the pipe to completely fill it. If the vent is too far from the trap or the drain is not properly pitched, the vent path will be broken.

You have a sag in the line which effectively double traps the fixture.

IF it worked, it would be because it is covering the symptoms, not curing the problem. IF the septic system is "flooded" the house line will fill with water, even without a sag or stoppage. Once the level covered the toilet
s connection, then any time the toilet was flushed it would have to either NOT flush, or force the trapped air up against the AAV, and since it could NOT evacuate the air it would have to escape through the sink trap.

Tom Sawyer said:

You have a sag in the line which effectively double traps the fixture.

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Yeah I will check when I can get under the house. WOuld a sag slow down the flow? I did the bucket test and man it flowed very well. I am going to have to draw it our and see what you mean by "double trap" the fixture.

hj said:

IF it worked, it would be because it is covering the symptoms, not curing the problem. IF the septic system is "flooded" the house line will fill with water, even without a sag or stoppage. Once the level covered the toilet
s connection, then any time the toilet was flushed it would have to either NOT flush, or force the trapped air up against the AAV, and since it could NOT evacuate the air it would have to escape through the sink trap.

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Thanks hj for the response but im not following what you are saying. Are you saying if the 4" trap worked it would be covering the symptoms? I dont think my septic is flooded. My perk rate is incredible. Just had the tank pumped. Bucket test poured 20 gallons of water like a champ.

This is going to suck if its really like Terry says just too much pressure for the existing wet vent system. I really want to replace all my toilets but if I cant remedy this im going back to the 2" flush valve and slower draining toilets.