Plumbing/drainage issue please help

[vanessa1357]

Hi I have recently moved into a 50 year old house. I have noticed that after draining water out of my bath and sinks a strange tapping noise starts in the pipes as if air is hitting into the water in the p trap and causing the noise. The noise starts about 30 seconds after the water drains and lasts various times depending on how long much water has been drained (the noise lasts longer if more water is drained). The water drains in all areas of the house fine and the toilets drain and fill up fine and there is also no sewage smell in the house. I had a plumber out a few days ago as the noise in my downstairs sink drain was really loud and he cleaned out that drain area with a vacuum type device and said it was filled with gunk/food etc but the noise is still there and in the bath pipes and other sinks. I will post a video for reference. Any advice would be great as I am so worried it’s going to be a very costly repair. Thanks

 

[vanessa1357]

Sorry the video won’t upload but it sounds like a loud tapping noise in the p trap area when the air hits the water in it.

 

[terryplumb]

Probably waste pipes expanding when hot water is running through them, and rubbing against timber or plasterboard etc

 

[vanessa1357]

Hi thanks for your reply, it happens when I drain the cold water as well the hot water

 

[terryplumb]

Hi thanks for your reply, it happens when I drain the cold water as well the hot water

Would that be because the waste pipes warm ,and cold water is cooling it causing contraction ,which would make the same noise ??
Really could do with hearing the sound,why can't you upload a video ??

 

[vanessa1357]

 

[vanessa1357]

Hopefully that works, thanks

 

[oldbutnotdead]

That sounds like a flat (or dipping) pipe run semi airlocking. Unlikely to cause any damage, it might get a bit stinky if it was left unused for a few weeks and it will be prone to debris buildup cos wrong gradient (or maybe undersized for the length of run)

 

[terryplumb]

Where do the waste pipes expel water, do they go into a vertical soil pipe externally or internally ?
Or do they go outside into a grid of some description ?

 

[vanessa1357]

The plumber said we have some sort of internal stack whatever that means and there is a manhole in the back garden which I can see water running through but not standing in. Sorry if that doesnt help much I know nothing about plumbing.