Why does this one toilet in my house flush poorly?

[JEG in Raleigh]

I don’t think there’s a solution to my problem without some serious demolition of my tiled bathroom floor, which I’m not going to do, but I’m hoping the pros can weigh in and confirm what I’m thinking is the cause of the problem. I built a new house and moved into it back in 2016. It’s on septic. It’s modern and unconventional. It’s built to Passivhaus standards for energy efficiency so there is 5” of polystyrene insulation under the slab and about 24” of gravel under the polystyrene. The front and back exterior walls are 10” thick precast insulated concrete. I took a lot of photos while the structure was going up so I’ll try to explain what is showing in the photos.

I’m old, been a carpenter/builder for 40 years, and am familiar with basic plumbing mechanics. I have 3 toilets in the house and all 3 are American Standard Model 2004 / Champion 4 one-piece toilets. 2 of them flush great. The one in my hall bath doesn’t. If you take a big dump, you have to double flush. It flushes fine when you pee, but it definitely does not flush as powerfully as the other 2 toilets in the house. The flush valve is fine, and water does not leak out of the tank. I check the water level in the tank regularly and it is right at the top of the flush valve. The characteristics of the poor flushing are not consistent. 25% of the time, it will flush a big dump, but 75% of the time it won’t. There is no rhyme or reason to when it works and when it doesn’t.

So, I took a lot of photos when I had contractors doing work during the construction and I was purging and organizing the photos and came across my photos of the waste lines being roughed in and plumbing rough-in after framing. I’ve circled the stack for the toilet and the sink in that hall bath in the photos of waste lines under the future slab. I also have a couple of photos of framing rough-in that show a vent stack where the sink will be, but no vent for the toilet. It looks to me like the waste line running from the sink that wyes into the toilet waste line, also serves as the vent path for the toilet. Is what you see in those photos the cause of my poor flush performance and if (big if) I were to seek to correct the problem in the future, what would I need to do.

Does what you see in these photos explain why I have poor flushing performance from this toilet? Is there anything I can do to improve the performance without tearing up the floor?


Thanks for your input.

 

[MicEd69]

The wye where the sink drain enters the drain line from the toilet should have been rotated up a bit so it would enter the drain line from above the centerline of the line. But that shouldn't really be too much of a problem is the sink is not draining during a flush.

Just a question, it's a little hard to tell, but is almost looks like the vertical to horizontal fitting from the sink isn't a 90-degree elbow. Surely, it's just the direction the picture was taken. It isn't a P-trap is it?

It could just be the toilet itself that is causing the problem. Even new toilets sometimes have flaws.

 

[Twowaxhack]

Before I chased this ghost I would buy a $200 toilet and install it. I’d pick one out I liked and if it corrects the problem great and if not you’ll most like benefit from a camera inspection.

 

[JEG in Raleigh]

The wye where the sink drain enters the drain line from the toilet should have been rotated up a bit so it would enter the drain line from above the centerline of the line. But that shouldn't really be too much of a problem is the sink is not draining during a flush.

Just a question, it's a little hard to tell, but is almost looks like the vertical to horizontal fitting from the sink isn't a 90-degree elbow. Surely, it's just the direction the picture was taken. It isn't a P-trap is it?

It could just be the toilet itself that is causing the problem. Even new toilets sometimes have flaws.

Thanks for replying. The fitting you asked about is a 90 and the sink does drain fine. I think will try a new toilet as you and Twowaxhack suggested.

 

[Rickyman]

Before I chased this ghost I would buy a $200 toilet and install it. I’d pick one out I liked and if it corrects the problem great and if not you’ll most like benefit from a camera inspection.

Yep, one of the workers probably dropped a vape machine down it and it's causing a partial blockage.