We have a bad odour (greeny smell, like algae or old water) coming from the floor waste in our bathroom. We’ve tried bleach, bicarbonate soda, etc and it comes back. Can we use caustic soda?
If these smells are from bacteria living in the build up of debris on the piping walls most chemicals are completely useless.
If you pour any chemicals in as soon as you use water these chemicals are flushed away.
Your best bet is to hire a licensed Drainer Or plumber and have them water jet these lines to a like new condition as the debris is also flushed away it scours these lines clean.
Carina, Stay away from the caustic stuff. Throw one part baking soda in drain and then one part vinegar. Let it sit a few hours and sometimes overnight. Do this periodically to all drains to keep them smelling nice. Bill The Local Plumber Tustin, California http://www.TheLocalPlumber.com