Water hammer from pipe outside property when bathtub drains

[wishiknewplumbing]

Hello everyone,

We recently had a scaffold put up on a two storey house to carry out a roof repair and, I am not 100% certain, around that time I started to hear a knocking sound in an outside pipe when the shower was used. Specifically, when the water drains from the bathtub (not when the tap is opened) into the outside pipe of the property. I have only noticed this with the hot water tap in the bathtub as we don't use the cold tap when showering. I have listened out for a sound when the toilet is flushed and when the bathroom sink is being drained and only noticed this knocking sound once, from both, immediately after the bath was used. This makes me think this is a bathtub problem- I think they all share the same pipe that drains outside of the property.

As an example, a family member took an eight minute shower and the knocking sound was heard within the first 40 seconds to 4 minutes when the water was draining down the pipe and then no sound from 4 minutes to 8 minutes.

Could this be something to do with the roof repair or the scaffolding that was put up? Prior to this, no sound like this had ever been heard.

I would appreciate any ideas/suggestions for a fix as I know that water hammer can be challenging to deal with.

 

[cross thread]

Do you have a hopper ? Possibly something fell in when roof was repaired

 

[wishiknewplumbing]

Do you have a hopper ? Possibly something fell in when roof was repaired

Hi cross thread, thank you for the reply, I just googled hopper but still unsure what it is?

 

[HERTS P&D]

down pipe hooper - Google Search

Andy

 

[wishiknewplumbing]

down pipe hooper - Google Search

Andy

Thank you, Andy.

I am not sure if we have this, I can check in the morning but- this is a general question to everyone- would this hopper be connected to the pipe which drains the water out of the bathtub? If yes, would a plumber have to dismantle this hopper to see if something is inside? And if the sound began when the scaffold was put up initially- not when the roofing work was carried out- would the scaffold perhaps have hit or damaged this draining pipe outside and perhaps that is causing the knocking sound?


All thoughts and ideas would be so welcome. Thank you...