Plumbing in the Home/Slow Flush


QUESTION: I live in one side of a duplex. In the last three months, the plumber has had to come out twice. Once because the toilet was backing up into the bath sink and the shower. The other side of the duplex had been having problems too.

The second time, the toilet was clogged. I live alone, and I started using the Scott's 1000 sheets which are highly dissolvable and paper thin (suggested by the plumber).

Now, the toilet is slow. When I flush, it does not do a normal flush. It does kind of a reverse flush meaning that water gushes into the bowl then slowly drains out.

I have plunged, plunged, plunged to no avail (thinking that perhaps something was stuck further down the line).

Yet, every single time I flush, there's water gushing into the bowl, and then it drains. It drains almost all the water out of the bowl and then there is a bubbling or sucking sound. It is not allowing a lot of water in the bowl. So, now when it is finished flushing, I hold down the handle to let more water into the bowl.

This is driving me insane. I put nothing but this thin toilet paper in this bowl - what is going on?

ANSWER: Kathy, What you may have is a plugged vent pipe. The most important part of any plumbing drainage system is the venting. I will try to give you a condensed reason. All toilet waste lines have to be a minimum of 3" in diameter. In order to flow properly they must be pitched between 1/8 to 1/4" per foot of horizontal run. Within 6 -10 feet from the toilet, there must be a vent stack that rises up through the building and out through the roof to the outside. This vent stack is what allows air to enter and be expelled from inside the drain pipe. When you flush the toilet, the water and debris is sent down into an empty pipe, this pipe is actually full of air, the air is pushed ahead of the water and if there is no place for it to vent out, it creates a vacuum and slows and sometimes stops the water flow. Once the water in the pipe passes by the vent opening in the pipe, the reverse happens. Air is drawn into the pipe from the outside and breaks the vacuum thereby allowing the water to continue on it's merry way to the sewer. Yours appears to be plugged. When you flush your toilet,  it swirls and then, when the vacuum is great enough, it tries to pull air through the toilet causing the toilet to loose all its water after the flush and you get a "gurgle or sucking noise. There are a couple of ways to fix this, one is to stick a drain snake or garden hose in the vent pipe in the roof to push or flush out the clog. Sometimes pulling up the toilet can give you access, it all depends on how your house was piped.
An other possibility: The main sewer is plugged.
You did not mention if you were on a septic system or a public sewer system. If it is a septic, have the tank pumped and make sure they clean the baffle in the tank. It could be just a simple issue of the main line is full and the tank needs service. My last bit of advise..Get a better plumber. Someone more experienced and not those franchised guys.


---------- FOLLOW-UP ----------

QUESTION: Unfortunately, there is no vent over the roof. I looked everywhere. Then my friend told that the vent is this small u-shaped metal thing attached to the wall outside that is closed and does not look as if it has been opened in years. It is actually painted closed.

I am on the public sewer system. I lived here for over 15 months without problems, and now, this is literally driving me insane.

I think I will have to get one of those plumbing snakes or that Johnny Jolter because the plumber just comes over, cleans out the pipe with his big machine, charges my landlord $75, and the whole process starts again.

So, I guess the only thing I can to help myself is let them clear it once more, ask them about the vent, and buy an auger and anytime, it is remotely slow, snake the darn thing.

Seriously, makes me long for the outhouse days.

ANSWER: Kathy, the plumbers who piped the house may have tied both sides of the duplex together and vented out on the opposite side of your duplex. Somewhere in that building there has to be some kind of vent. An auger is only going to unclog a toilet. It isn't long enough to get into the line. Since you are getting a back up in the other fixtures the clog is further down the line.
Lastly, if we go back to the era of the outhouse...I'm out of a job! ;-)

---------- FOLLOW-UP ----------

QUESTION: What will the vent look like? I no longer get backup in the other fixtures; that was only the first time. Now, it is just the toilet.

Can you describe what I am looking for? I can tell you that it is not on the roof because I have looked.

Nah, you wouldn't be out of a job; your job would just change to building outhouses instead of unstopping messes . . .

Also, going to try to do the toilet ports; doesn't hurt.

Btw, this house was not original built as a duplex; my side was added later. Don't know if that helps.


Check out this link

Vent will be a 3 or 4" pipe sticking out of roof about a foot or so if the house was plumbed properly.

If you are only getting a slow flush and no gurgling or water being sucked out of the toilet, then perhaps only the toilet is clogged and needs to be augured out

Plumbing in the Home

All Answers

Answers by Expert:

Ask Experts


Jay Nicholas


Plumbing & Heating (warm air, hot water & steam heat)


40 years in the business, 35 years as a lic. master plumber in NY State. Retired

Graduated Magna cum laude at the School of Hard Knocks

Past/Present Clients
Commercial, residential and light industrial. You name it ...I have probably worked on it

©2016 All rights reserved.