Hello all,
I have a fairly small, old house with a similarly small, mostly old (and probably incorrect) plumbing system. Upstairs is a toilet that had a mechanical vent in the wall behind it. In the downstairs bathroom is a washer, shower, sink and toilet, all going into a septic tank. The downstairs appliances were built without any vents, but the toilet did have a 3″ pipe extending from below the closet flange into a wall cavity, and traveling about 7′ up and dead ending with a cap on it. There are no through the roof vents.This system worked without any apparent problems for 8-10 years.
In the past few months, the upstairs toilet has started to bubble (furiously at times) when the downstairs toilet is flushed. Not every time, but enough to make the user of the upstairs toilet nervous, and occasionally unhappy. My first thought was that the mechanical vent had failed, so I replaced it with an AAV (Magic Vent by Rectorseal). Still the problem persisted, but again, not every time. I cut open the wall behind the downstairs toilet, shortened the 7′ pipe to 3′, and installed another AAV. Still, the problem occurs, but not every time.
What is going on? I assumed the bubbling upstairs toilet was due to the downstairs toilet not being vented properly, but it is still happening. The fact that it worked for years with only a mechanical vent upstairs keeps haunting me.
Any ideas? Could it be an intermittent clog somewhere? The septic tank isn’t full. It’s only been a few years since it was emptied.
Thanks!
Here’s a drawing of the current setup:
Replies
Dollars to donuts your septic tank is failing. If not that then there's likely a partial clog between downstairs toilet and the tank.
But what do you mean by "mechanical vent"?
(And yes, the setup is out of compliance about five different ways.)
Hi Dan,
Thanks for the reply. When you say the septic tank is "failing", exactly what does that mean?
By mechanical vent, I mean a spring operated $6 part,View Image
as opposed to a gravity operated $25 part. View Image
I agree with Dan. The bubbles come when the lead pipe to the septic fills up past the bottom of the ground floor vent stacks. Whever I notice a toilet bubbling I start looking at a septic problem or a clogged drain. I would snake the drains first, and then get the tank pumped (do both).
It may just be that the scum in the tank is causing the line to back up but have the guy inspect to be sure the intake and exit baffles are OK.
Yeah, "only been a few years"
Yeah, "only been a few years" since the septic was pumped is plenty of time for it to clog, especially if it's not serviced regularly.
Both of those are "air
Both of those are "air admittance valves". And the operative word is "admittance" -- they let air in but not out.
All plumbing systems require one "true" vent that can let gasses escape, and that goes double for a septic system.
Thanks for all the comments. I'll try snaking the drains first and take it from there. I appreciate the advice!