Septic System Problems

[TheFarmerInAdell]

I have a old septic system put in WWII era. Small tank (500 gallons). Last spring I started having trouble with the 1st floor toilet bubbling when a large amount of water went into the system (drain the tub for instance). It was only the 1st floor toilet, not the sink. There is no gurgling sounds from anywhere indicating the vent is plugged. In fact, there are 2 vents in the system (one tied to the 1st floor bathroom, one tied to the 2nd floor bathroom/laundry room, plus an AAV on the kitchen). The venting on the 2nd floor is new. I installed it when I added a bathroom and moved the laundry room up there with all new plumbing about a month after this trouble started. I had the system pumped when this trouble started, assuming the tank was getting full and blocking the exit to the drain field. The pumper said everything was good, and no "runback" -not sure if that's the right term, basically when he ran water from the tank into the drain field it didn't come back indicating a blockage. Also the drain field vent was dry. The bubbling starts after probably 30 gallons or so in less than a 2 hour time window, doesn't matter where the water comes from, and the bubbling always comes from the 1st floor toilet. Also, any other fixture will drain properly, but the 1st floor toilet will back up when flushed if it's gone to the "bubbling stage". I've attached a diagram of my system to give some insight. If I open the inspection cover at the piping leading to the tank the problem seems to go away indicating that the air is not escaping from the system. Why would the air escape there, but not through the vents in the roof? I'm at a complete loss as to the cause of this...

Anyone have an idea on the cause of this? I don't want to install a new septic system if I don't have to right now. I know I need a new one in the future, but I'd rather wait to install it until I have the area for it cleared first.

 

[CobyRupert]

Your diagram may be more "intuitive" if you'd drawn 2nd floor on top, 1st floor in middle, tank on bottom and vent connections at appropriate elevation.

It sounds like a venting problem. There's also the twist that you have an air make-up valve at kitchen sink.

Any chance a vent pipe got frozen?

 

[TheFarmerInAdell]

I sounds like a venting problem. There's also the twist that you have an air make-up valve at kitchen sink.

Any chance a vent pipe got frozen?

I would have thought a vent problem at first, but adding the 2nd floor vent didn't change anything.

It happens in summer, too. I sure hope the vent isn't frozen in summer! (it is Wisconsin, though...)

 

[Beltzington]

I am not a plumber but have installed and repaired several plumbing issues and I agree, it sounds like a vent issue on your 1st floor. Get somebody to make sure you're not overflowing the sink and toilet and stick a hose in your 1st floor roof vent and see if drains. Maybe being on your roof this time of year is unsafe, but it was 80-degrees here in Georgia yesterday.

Good Luck.

 

[CobyRupert]

So it's "venting" through 1st floor toilet, even when you've run water from 2nd floor, even though you have a 1st floor vent.

So....why doesn't it vent through first floor vent? :confused3:

 

[Beltzington]

I would have thought a vent problem at first, but adding the 2nd floor vent didn't change anything.

It happens in summer, too. I sure hope the vent isn't frozen in summer! (it is Wisconsin, though...)

You replied while I was responding
If your diagram is fairly accurate the 2nd floor vent is not going to provide much or any venting for your first floor drains.

 

[TheFarmerInAdell]

I will try to run a snake through the 1st floor vent.

I'd also like to be more specific, it is not gurgling (sucking water) it is bubbling (pushing air out). Not sure if that makes a difference. I would think that any air pressure built up in the system would push out the 2nd floor vent if the 1st floor vent was plugged. When I drain the 1st floor tub (down stream from the toilet) I get air bubbling out the toilet.

The vent pipe on the 1st floor is easily accessible from a ladder so I'll try a snake on it. I don't have any running water outside right now so I can't do that trick.

 

[CobyRupert]

It happens in summer, too. I sure hope the vent isn't frozen in summer! (it is Wisconsin, though...)

Is there cheese stuck in it?

 

[TheFarmerInAdell]

Is there cheese stuck in it?

I wouldn't be surprised. We have tons of cheese here! Not sure if I would eat that cheese though...

 

[jfh28]

you may also have a partial blockage on the drain lines which is backing things up temporarily until it clears....this would force air upstream until it clears and also account for the toilet backing up....buildup over the years especially from tub soap scum and hair can slowly reduce the width of the drain line......I would pull the toilet and snake the drain to the tank if you can ......Jack