back syphonage

[Col25]

Not sure if my description is correct. Have just bought old flat which has been empty for 9 months. Every thing fine except everything rather old.
Suddenly other day noticed lot of gurgling in sink in bathroom then later heard and saw water coming into the bath through the plug hole. After a few minutes it emptied itself. I think it coincided with a bath or shower in the flat above.
Any advice about causes and cures.
Thanks

 

[ChrisR]

You have a blocked waste/drain pipe somehwere. If it were plumbed properly it would be very unlikely to happen anyway.

 

[meldrew's_mate]

You have a blocked waste/drain pipe somewhere....

...and the blockage is downstream of your flat. Lift the inspection covers and observe the flows. Rod the drain back from the first "empty" gully.

 

[Col25]

Thanks for the replies. As it clears after a few minutes does that mean it is partially blocked.
What do you mean " if it was plumbed properly I would't have the problem"? I (or someone else) will be putting in a new bathroom suite soon so is there something I need to get done.
Thanks.

 

[ChrisR]

Well, drainage design isn't quite as trivial as it might look.
A blockage in one place shouldn't affect anything else. Eg all the thin pipes should go to the stack pipe (which generally doesn't block) separately. It doesn't often happen that way - which is why bathroom basin wastes can make the bath trap bubble when they share a waste pipe.
Yes you have a partial blockage, probably hair and soap, but could be plastic. I'd first pour a large pan full of boiling water down the waste, which would hopefully soften the grot, then get a bottle of serious drain cleaner which contains sulphuric acid and slowly pour that down. It's very nasty stuff but it often works - unless there's plastic.

Never NeverNeverNeverNeverNever mix drain cleaners with anything else like bleach, caustic soda etc. If anything else has been used flush it best you can and try a little - cold.