Sounds from soil stack

[redlagoon]

First of all, i realise this is an extremely generic query and unlikely to produce a specific answer. My intention is only to see if anyone has experienced something similar or might suggest avenues that i can pursue to investigate the matter further.


A short time ago, i instructed some builders who replaced the rear soil stack that receives flows from an upstairs bathroom and loft shower.
This was part of a larger job and the property was empty at the time.

I have now got the situation where if anyone uses hot water in either of these 2 bathrooms, there is a knocking noise emanating from the soil stack. It sounds like it's coming from somewhere near the connection from the 1st floor bathroom. However, there is now an extension built at the rear and the connection is boxed in so i can't see or pinpoint the noise easily.


Looking for suggestions on what this might be and how to locate the issue.....

 

[doitall]

Easy

As the hot water drains away the pipe expands.

The pipes is touching wood, plaster etc perhaps ina boxing or where it goes through the ceiling.

 

[wedge69]

Cor, you have answered a question that had been bugging me for ages!

Our soil pipe is boxed in and runs from the bathroom down through the kitchen. I always wondered why there was a knocking sound (almost like a dripping) when someone used the shower, but not when the chain was flushed.

Now I know!