We have never had any problems with smells in our 3 bed bungalow in Spain, until we had a new bathroom built next adjacent to the old bathroom. The new bathroom pipework was connected to old bathroom wastepipe which feeds into a septic tank (100metres from house). The old bathroom does not smell, but there is a strange smell in the new bathroom.

We have put in another stink pipe closer to the house (in case the old one next to garage where septic tank is located was perhaps blocked. (and now I can smell something outside the house, whereas before I couldn´t. But there is still the same smell in the new bathroom. We have had the septic tank emptied. The plumber who installed the new bathroom has put down a camera and said that there is no blockage - but how can we tell if there is perhaps a tiny crack causing a leak?

Another possibility is that an overflow pipe from large water cistern under the house has overflowed and there is a pool of stagnant water under the new bathroom causing a smell. We are finding it impossible to locate the problem. In desperation, we have put some bacteria/enzymes down the loo today to see whether that helps.

How can we know whether the smell is dangerous or not?

Can you point us in the right direction please.

Thank you!

What thoughts were offered by the plumber, did he smell the odor and identify it?

The plumber´s solution was to put in another stink pipe closer to house, outside kitchen (7m from new bathroom) and put down the snake camera to identify any blockages.

Unfortunately, the plumber is now getting stroppy, and says it has nothing to do with his workmanship. Last year, when he installed the new bathroom, the smell was much worse, and he had forgotten to put silicone around base of the toilet. He did this, and the smell slightly improved for a while. Now he says he can´t smell anything - he is being difficult. He says that if all 3 bathroom pieces have their U bends - it´s not possible for smells to pass through the water - This I know is not the case, as gases are heavier than water.

The smell is always there, and we have the window open all the time. Sometimes it is not as offensive. Occasionally it smells slightly 'sweet'?

I wonder whether the smell is coming from the bathroom rather than from the septic tank.

Someone suggested putting 1/2 gallon of bleach down shower/loo/sink, but won't this harm the septic tank. Or should I wait for the bacteria/enzyme sachets I put down the loo yesterday to work, before I try bleach??

If there is a slight leak, how can we detect this?

Hello, is there a exhaust fan in the bathroom ? If so is the sewer vent stack on the roof far enough away that sewer gasses can't get drawn into the room by a backdraft? Or you might consider having a smoke test done to see if there is a breach in the system, if there is you will most certainly see smoke coming from somewhere showing you where exactly the sewer odor is coming from. Goodluck ----Zeke----

Hi Zeke

Thank you for your reply. There is no exhaust fan in the bathroom, and the sewer vent stack on roof is on the other side of the house about 10metres away.

What is a smoke test? They don't seem to do that here in Spain. Could you explain it please step by step, so that I can understand. Thank you, Carolina

Good morning Carolina.
A smoke test is simply placing a smoke bomb in your drainage system and checking the joints for any leakage.

the plumber is now getting sloppy, and says it has nothing to do with his workmanship. Last year, when he installed the new bathroom, the smell was much worse, and he had forgotten to put silicone around base of the toilet. He did this, and the smell slightly improved for a while
This points to a wax seal on the toilet that has ruptured allowing sewer gas to escape into your bath room. I don't think adding another vent will help a bit. Sounds like your plumber was stumped and just threw that out in hopes it would help. I would pull the toilet and reset it using a new wax ring.

Another possibility is that an overflow pipe from large water cistern under the house has overflowed and there is a pool of stagnant water under the new bathroom causing a smell.
This condition is unhealthy and should be corrected ASAP.

The plumber says that if all 3 bathroom pieces have their U bends,("P" traps) - it´s not possible for smells to pass through the water - This I know is not the case, as gases are heavier than water You are in error about that. This is why we have traps on all fixtures. The water acts as a seal against sewer gas. But I would take care of the lake of stagnant water under your house and replace the wax seal. Good luck, Tom

I agree with Tom and further think you need a new plumber. If you were getting sewer gas from the base of the toilet the correct fix is not silicone. If this is how he fixes things I can only imagine how poorly he installs things. PS cubic foot of water weighs 62.4 lbs while a cubic foot of air weights only .8 lbs