p trap in 4" waste pipe


  #1  
Old 08-03-16, 10:15 AM
Q
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p trap in 4" waste pipe

I have a family member who has property in a country where code requirements are not exactly strict
The septic tank smells in the house.

There is a section of the plumbing for the main waste pipe that comes from the house and runs a70 ft (slight angle from horizontal) before running down 20 into the septic tank.

There is either a problem with the venting at the top of the house - the pipe does not extend beyond the roof but rather into a little roof cap.

No-one knows if there is an open pipe in the house (in the concrete cavities) or some other problem but when the central ventilation/AC is turned on, septic tank smell comes out of the AC vents.

To try and improve this, they added a vent in the main waste pipe and knocked a hole in the wall of the house underneath one of the toilets!
I can only assume this was a way to increase the ventilation of the tank but it has made no difference.

Can you add a p trap in a long section of 4" pipe or will this cause back up problems?
 
  #2  
Old 08-03-16, 11:02 AM
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Some areas do require house traps (U-traps to be precise), so it shouldn't cause any problems.

Since the smell is noticed when the AC is on, I think it's one of two issues, neither really having to do with the plumbing system:

1) Where does the condensate drain from the AC? If it drains into the sewer piping, try changing it to drain outside. The condensate drain can pull air up from the drain pipe, which if not properly air-gapped and trapped, can pull sewer gas into the air system.

2) Try pouring some bleach down the condensate drain line. I had this exact problem and it turns out that there was gunk/mold/mildew growing in the condensate drain and condensate pan. The pan can be quite difficult to get to, but the drain is a good place to start. It wasn't actually sewer gas, but instead the mildew being pulled back into the system. Ick!
 
  #3  
Old 08-03-16, 11:25 AM
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It smells even when AC is off.
For example, I I turn on a bathroom extractor fan, you can then smell all the sewer gas in that bathroom coming through the ceiling cavity.

Main issue is accessibility I think. The 70ft run is just on the underside of the ceiling in a very high basement room - you can only reach the ceiling by being on a long ladder so if it ever blocked it wouldn't be easy to get to - not for an old person anyway.

One possibility is on the run that goes down into the tank but it's a vertical run so it would have to be some type of s bend?

Also, if I do this, won't the tank then have no venting at all?
 

Last edited by qwertyjjj; 08-03-16 at 01:28 PM.
  #4  
Old 08-04-16, 09:37 AM
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If I do this, won't the tank then have no venting at all?
 
  #5  
Old 08-05-16, 08:01 AM
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on a 70ft run, doesn't waste stay in the pipe?
You'd have to have loads of water flushing to push it all the way along the 70ft?
 
  #6  
Old 08-25-16, 04:18 AM
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Condensate lines look like this. I cannot see them draining into anything:






 
 

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