Bubbling toilet and shower

[jpb116]

- I have a basement bathroom with 2 sinks a toilet and a shower.
- The home has 2 septic systems so the basement setup has a dedicated septic system.
- When my sinks run the toilet bubbles and burps. If you were to flush it while it were bubbling the water would not go down and the shower will spurt a little bit from its drain.
- The toilet drain is in the concrete and my assumption is the shower drain is as well.
- there is no sewer gas smell in the room
- Nothing overflows.

There are two vents I can see, Vent #1 in the picture is an under sink type and the #2 is a long 2" vent that seems to twist and turn up through the attic and out. My assessment, from what I can see without demo'ing half of the house is that this vent #2 has quite a few sharp bends in it before exiting.

There is an iron domed clean out outside the house

When I bought the home 3 years ago this condition existed and I had a plumber snake out from the toilet to the tank to attempt to remedy the issue, which seemed to help, although I can't say for sure.
My only thought is that there is a venting problem somewhere. Does anyone have any thoughts? What is occurring that causes the bubbling?

[Inspektor Ludwig]

Sounds like you have a positive air pressure situation. If the vent under the sink is an "AAV" or a Studor vent then it would only alleviate a negative pressure situation. When you have a plug of water going down the drain the vent, if properly ran, would allow positive pressure (air in front of the water) to escape and then allow negative pressure ( air behind the water) to come in and would balance the pressure in the plumbing pipes. When you run your sink the air has no place to go. Depending on how the vent was pulled off of the toilet and how the sink waste line was tied into the toilet drain can also be a factor since the you'd think the positve air would exit out of the toilet vent, which should be the case. The fact that the toilet does not flush tells me that the vent is not installed correctly. So all of this positive air pressure has to have somewhere to go and that means out of your toilet, hence the bubbling and out of your shower which explains the splashing of the trap water as the air escapes. I have a feeling that your shower may not be vented correctly if not at all. I would check to see if the shower has a vent and if the toilet has a vent installed correctly. If the vents on the toilet and the shower are ran correctly then the Studor vent under the sink should be ok for the application but I strongly advise running a conventional vent for the sinks. If the plumbing system has a venting problem this causes the solids to drain very slowly and can cause the line to back up which would make all of the other problems worse. And of course I have to ask the obvious, has the septic tank been pumped?

[jpb116]

The tank is pumped yearly, and being only a basement bath tank means it doesn't get used too often.

On the vent subject I should mention that the two vents are about 3 feet apart. This is a small room. The under sink vent looks like an add on where the 2" vent pipe next to it is house built original. i don't know if this basement had a bath built with the house or if this is a handi man (or not so handi) addition over the years.

[Inspektor Ludwig]

It sounds like a venting problem. You really need to check and see if 1. the shower has a vent and 2. the toilet is venting correctly. The only way to know for sure without breaking up the slab is to camera the lines. This can tell you how the piping was ran, what size pipe and where any vents may be pulled off. Other than that you'll need to find a way to get access to the drain piping. My guess is the home did not originally come with a bathroom in the basement, it was added later by the homeowner and probably not done right.

[hj]

A flooded septic system, (for whatever reason, such as heavy rainfall), will cause the same symptoms as a clogged main sewer or vent problem. The fourth possibility, the tank itself, does not seem to apply if your tank is being pumped periodically. There is NO WAY to tell which of the three problems you have without a complete testing of the system, and possibly examining the tank condition itself.

[jpb116]

So, if the tank is pumped and the environmental conditions are consistent... is the vent config in the drawing correct enough to be functional? Another question... Does the outside clean-out act as a vent or is it closed? Mine looks older with a domed top and some for of gap around the dome

[Inspektor Ludwig]

Does the piping going to the septic tank have proper grade? If any portion of the main is backgraded, that could cause a problem too. The clean out is not a vent. The vent system you have in your picture is not correct as shown. The shower needs a vent and the sinks should have a conventional vent instead of a studor. I wonder if that vent for the toilet is actually for the toilet or if it was for something else. If a vent was that accessible, why would they install a studor vent instead of just tying into the toilet vent? Between the septic tank, lack of proper vents, everything buried in concrete and a homeowner install , it could be anything at this point. You need to do some basic troubleshooting based on the advice given here by the plumbing pros. I suggest calling a plumber to help you figure this out.