Septic Tank Problems?

I just bought an old farmhouse (really good deal) an am going through all the repairs that need to be done and now have a puzzle.
When a large amount of water is flushed down the pipes (i.e. bathtub emptying) the basement fills with sewer gas. Found a clean-out cover rusted out (and now fixed) but still having the gas odor.
I think that when the waste water enters the tank, the gas gets pushed back. After the fix it has dropped noticeably, but it appears it has now been directed to the tank vent.
There's still some gas in the basement, and a fairly good stench from the septic vent, have I been living in the city so long to forget that this is normal?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
There's got to be something wrong somewhere, there should be no smell inside the house. Have you contacted the previous owners or are they no longer on this planet?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Check to be sure that the vent pipe for the bathtub is also clear. It sou nds like there is a problem with the venting system. The toilet may be cau sing the same problem except that there is not a large enough volume for a long enough period of time. Verify that the vent pipes are clear all the w ay to the roof.
Dan
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Does the tank have its own vent - separate from the roof-top plumbing vent ? < all three homes that I've owned were septic systems - with only the roof-top plumbing vent > What is the elevation of the septic tank inlet pipe - when compared to the cellar floor ? < all three of mine were about 5 feet above the basement floor > The tank on my present home is only about 8 inches below surface - earlier homes were about 12-14 inches down. I've never had any problems - never worried much about them .. Maybe you'd want to pump out the tank and have it inspected - - the baffle on the outlet is important. The consistancy of the septic waste might tell you something also - the tank-pumping guy usually knows a thing or two. Good luck. John T.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 03/24/2017 3:02 PM, Bob wrote: ...

Can't unless there's a line w/o a trap or a trap of a long-deserted or unused trap is empty; if the house has been unlived-in for a while it's quite possible some have evaporated enough to leave a path if not everything is being used.
--


Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Fri 24 Mar 2017 02:54:17p, dpb told us...

We have a number of plumbing fixtures that are seldom used, so we routinely flush those toilets and run water in the tubs and sinks to make sure the traps don't run dry. We're not on a septic system, but all traps, regardless, can potentially run dry if not used.
--

~~ If there's a nit to pick, some nitwit will pick it. ~~

~~ A mind is a terrible thing to lose. ~~
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 3/24/2017 6:04 PM, Wayne Boatwright wrote:

Yep, that's the first thing to check. Find every drain and dump a small bucket of water down it. If any of the traps are dried out, the plumbing stack vent will not have any effect on the situation he describes. It really doesn't take all that long for a trap to dry out if it's not constantly doing its job.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 03/24/2017 3:02 PM, Bob wrote: ...

...
I'd assume since house is old the vent is in the waste line leaving the house, not a vented tank (I guess some are done that way, never seen it though and spent >50 yr in houses on septic systems).
I'd suspect besides the other note on dry traps possibly there's a basement floor drain or unused washer connection or something down there maybe?
Unless the exit vent is blocked or there's a leak in a vent itself, other than coming back through a dry trap there really just isn't a path for gas back into house...it would take quite a lot of pressure to force it back through a full trap.
--


Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Bob wrote:

in a very old home it could even be a cracked pipe some place.
songbird
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

What do you mean by the "septic vent"? Normally, your main drain line should have a vent pipe that runs all the way up to the roof. There should also be individual vents for each fixture (sinks, toilet, tub, etc.).
Some older homes may not have vents for each fixture. This creates a vacuum in the drain line when you dump water down the drain (like the glug glug you get when pouring water out of a bottle). For something like a sink there's usually still air space in the drain pipe that allows some venting. But draining a bathtub may completely fill the drain pipe, so it will be trying to suck air from any place it can in the system.
If the vent extends through the roof, but you're smelling gas in the basement, you have a leak somewhere. If no water is leaking out anywhere, it's probably a leaky vent pipe.
You might try applying some really soapy water around all the joints in the pipe and see if the soap bubbles up anywhere when you drain the bathtub. Though in theory, it should be sucking the soap inward and not exhausting gas out.
Assuming you have a roof vent, you may want to check that it is not clogged with a bird nest or something. I recommend getting a cap for the top that allows air to enter and gasses to escape, but keeps out the birds (available at any home center).
Good luck!
Anthony Watson www.watsondiy.com www.mountainsoftware.com
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sunday, March 26, 2017 at 12:11:55 PM UTC-4, HerHusband wrote:

Older homes I've seen here, built 1950 and earlier, don't have a main vent that runs out the roof. They have one on the sewer line, near ground level, where it exits the house. Then they have vents for bathrooms and such that do extend out the roof.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Interesting, I haven't seen that (in my very limited experience).
My in-laws house is about 100 years old. They had a single main roof vent (only 2 inches for the whole system), but none of the individual fixtures had any vents at all.
Anthony Watson www.watsondiy.com www.mountainsoftware.com
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 03/26/2017 11:13 PM, HerHusband wrote:

Ditto farm house here ca 1916, and I, too, don't think knowingly seen a house entirely w/o stack vent (then again, not something I routinely inspect on drive-by :) )...
--


Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 3/24/2017 4:02 PM, Bob wrote:

Agree with other comments. My tank is not vented but house vents should take out odor. Traps should be filled and vents clear.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Bob wrote:

Not normal. If you haven't had the septic tank pumped out, it may be backing up. You should have it pumped out AND have it inspected to make sure it is in good working order. It's possible you may need a new septic tank AND a new drain field.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.