Hi,

I have moved into an 18th century cottage, but the house has been redone about 15years ago. The property has a septic tank.

The shower is on the second floor. When the shower is used there is a bad odour, I think coming from the drain. This happens 90% of the time in the evenings and the smell is very strong. It happens 40% of the time in the mornings, however the smell is not as bad. All the other taps and drains in the house do not emit this smell.
There is a 'shallow' S trap due to the floor being really close to the bottom of the bath/shower. And the drain pipe runs almost parallel to the ground around the bathroom until it drops down in the corner. The water runs down the drain sporadically, sometimes its fine, and other times there are pauses in the drainage,
I have also been advised that due to having a septic tank, pouring bleach down the drain will not be good for the septic tank.
Is this smell from the septic tank or is it something else?
What can be done to stop this unpleasant smell creeping into our house?
Please help
Ben

You have sewer gas coming back in from your septic tank. DO NOT PUT bleach into your septic tank. You may not have a proper vent installed on your trap and/or the trap is not adequate. Due to the age of the home I can't give you much more. Call a plumber who knows what he is doing.

A vent pipe is either broken or incomplete. Does the toilet rock?

Thanks for the advise!

The toilet doesn't rock...

What is a Vent? Sorry I am not very accustomed to plumbing terminology.

And is the trap the S bend under the drain hole?

This may have nothing to do with your sewer... it may be sulfer bacteria coming through your pipes... I've gone through the whole process and it ended up being a simple issue with the filtration system on the well...

First question is this a well system, or city water?

Secon question, do you have any filtration systems on it...

"What is a Vent? Sorry i am not very accustomed to plumbing terminology."

On a two bath house, as a rule you have three vents. One each on a bathroom lavatory that vents the group, and a kitchen sink vent. If you have a laundry room that could be another vent. Sometimes we tie them all togather in the attic so that we only have one pipe coming out the roof. This is called reventing. It is possible that the bulder terminated the vents in the attic but I don't see how that would pass inspection. A vent that does not terminate through the roof is called a local vent. I am giving these terms so that when you talk to your plumber friend you will be on the same wave length. There is only one way to prevent sewer gas fron escaping from a local vent that terminates inside a wall. This is a mechanical vent that is spring loaded so that it lets air in to vent but stops sewer gas from getting out. This vent is called a Studor Vent. A plumbing drainage system has traps on each fixture. These traps keep sewer gas from escaping into your house. On a unvented system the water draining sets up a suction that syphons the water out of the trap letting sewer gas out into your house. I have tried to explain how vents work and the different kinds. You asked how important venting is. Vents are necessary for a plumbing system to function.

"And is the trap the S bend under the drain hole?"

Yep! That's a trap OK, however, if you have a "S" trap instead of a vented "P" trap then the fixture's unvented. Regards, Tom