ᐅ The siphon or shower drain empties when the toilet is flushed.

Created on: 8 Jan 2021 11:26

Hello everyone,

We have been living in the house for about 7 weeks now. During the first 3 weeks, the guest bathroom with a shower on the ground floor was our main bathroom, as the actual main bathroom in the attic wasn’t finished yet. For the past 4 weeks, the guest bathroom has mainly been used for toilet visits (too lazy to go upstairs) but rarely for showering. Now the bathroom sometimes smells a bit like sewage. The odor comes from the shower drain. After 2-3 toilet flushes, the drain and probably the shower trap are empty, allowing the smells to come through. Is it normal for shower water to be drained when flushing the toilet? Where should I start looking to find the problem?

Attached are 2 pictures. One shows the plumbing rough-in. Maybe there’s a visible mistake in the pipe layout. The other shows the almost finished shower drain.

Maybe someone has an idea.

Thanks and regards

Geberit WC-Rahmen im Rohbau-Badezimmer, sichtbare Abfluss- und Wasserleitungen am Boden

Badezimmer unter Renovierung: graue Großformatfliesen, Duschbereich mit Abflussrinne.

Joedreck8 Jan 2021 14:45

#19

It is also possible that you have two pipes leading to the sewer. And the bathroom downstairs simply was not connected to the vent pipe.

pagoni20208 Jan 2021 14:46

#20

Tassimat schrieb:

(Ventilation of the wastewater pipe, not the indoor air!)

Exactly - correct. THIS ventilation, so there is no misunderstanding.

Stefan2.848 Jan 2021 14:55

#21

Tassimat schrieb:

(Ventilation of the wastewater pipe, not the room air!)

🙂 Of course. I am obviously not referring to anything related to the ventilation system. I have now tried to trace the pipe routes using old photos. And if I understand this correctly, it seems that the lower bathroom and the upper bathroom each have two separate pipes that only join “underground.” That would obviously be a problem. I have attached more photos. The main bathroom upstairs is correctly connected. The one downstairs apparently is not.

White PVC drain pipe on the ceiling with clamps, next to copper pipes and heating unit.

Geberit flush tank within wall frame, blue steel structure, visible pipes and yellow handles.

Attic: wooden beams, silver insulated pipe next to white foam insulation on concrete wall.

Boiler room with copper pipes, valves, circulation pump and heating boiler.

Tassimat8 Jan 2021 15:00

#22

Well, this is probably a mistake in the architect’s planning 🙁

I have no idea what can be done about it now.

Please share what solution the plumber suggests, I’m interested to know.

Tolentino8 Jan 2021 15:16

#23

Ventilation valve directly at the toilet.

Joedreck8 Jan 2021 15:18

#24

Tolentino schrieb:

Ventilation vent directly at the toilet.

I have the same setup at my bathtub. Works without any issues.

ᐅ The siphon or shower drain empties when the toilet is flushed.

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