My house was built in the 1930s. The basement has been finished with tile and carpetted areas.

We have a common occurence of sewer smell in the basement. I know of two places that this might be comming from:

1) PVC drain pipe from the bathroom sink slips into an iron pipe and there is no slip ring or gasket on that connection. Sometimes it seems this is the source of the smell

2) A drain in the concrete floor of the former garage was filled with cement. Other times, it seems this is the source of the smell.

I really don't want to tear up the floor to access these areas unless its the only way to fix this problem.

My suggested solution is to dig up the sewer pipe outside the foundation of the house and put in a p-trap on the main line. Will this work or will it cause other nastier problems like plugged lines?

Thanks in advance for any advice.

Item # 1 is a definite problem and needs to be corrected. After correcting it, see if the smell disappears. If not, move on to # 2.

if he is describing the tailpiece sticking into the trap with no slip nut, that is a problem but should have nothing to do with a smell. it is on the inlet side of the trap if i read the post correctly?

The option of installing a "house trap" on the main sewer lateral can cause even more problems of blockages. I'm not sure but i dont think that the main plumbing codes allow them? Local codes might allow them under certain circumstances.

Given the nothing but bad news that i've heard about them i'd steer clear of installing one.