Water in sink trap bubbles when shower is running?

[humanracer]

My shower/bath and sink share the same drain. No water travels to the sink when the shower is on. However when I have the shower on the water in the sink trap starts to bubble. It doesn't come up the sink but I can see it bubbling away in the trap. Is this an issue with pressure? What would cause this?

 

[CBW]

Sounds like a partial blockage or incorrect fall on wastepipe. It’s not pressure related.

 

[Hugh Jaleak]

Where do they all drain to? Possible blockage downstream somewhere, and as the water cannot get away properly, it is displacing the air in the pipework as it fills up, this air is then finding the easiest escape route, i.e. the basin trap.

 

[humanracer]

Where do they all drain to? Possible blockage downstream somewhere, and as the water cannot get away properly, it is displacing the air in the pipework as it fills up, this air is then finding the easiest escape route, i.e. the basin trap.

Thanks. The water in the sink goes to a drain outside via a pipe on the floor. This outside drain is shared by the bath/shower. So you think the block is potentially between the bath and the sink under the floor?

Last time this happened and there was an actual sink blockage, the plumber used "one stop drain cleaner" which I believe is like acid. He left some of the bottle here. Maybe I should pour the rest down the pipe in the floor.

 

[CBW]

If it’s like acid, make sure you’re careful and wear suitable gloves. You could try a plunger or a drain auger.

 

[Madrab]

one stop drain cleaner

Do you mean One Shot? If so, please don't use it, it's concentrated sulphuric acid and should only be used by professionals. It's not really a DIY product and it shouldn't have been left with you, especially if he didn't make you aware of the dangers of using and storing it.

 

[humanracer]

Do you mean One Shot? If so, please don't use it, it's concentrated sulphuric acid and should only be used by professionals. It's not really a DIY product and it shouldn't have been left with you, especially if he didn't make you aware of the dangers of using and storing it.

Yes one shot instant drain cleaner with sulphuric acid.
It did get the job done last time although it did smell of eggs.
I can't think how else to fix it. An auger won't go that far.
would you advise against using it even if I wear gloves and goggles?
Maybe I need to call a plumber.

 

[CBW]

An auger won't go that far.

How far is it?

 

[humanracer]

Problem solved thank you. Went outside and there was a dead mouse at the end of the pipe!