Is the inner end that is attached to the elbow and it leaks inside the wall. If is outer, then yes, can see water mark.

A plumber will also do the same b4 hacking the wall.

This post has been edited by mini orchard: Jun 1 2021, 09:05 AM

tighten all the fitting connections which attached to the wall and monitor first

the inner end leak can still see water seeping down the wall from bathroom side.

One must try all cheaper possibilties b4 hacking the wall.

Leaking is not an easy problem to solve. Sometimes is obvious and can be rectified easily.

If the wall plastering is with bad cement rendering, it will not leak outside the wall.

Is definite internal leaking of the piping connections. Try those can be seen. Those hidden, no choice have to hack.

This post has been edited by mini orchard: Jun 1 2021, 09:46 AM

Don't waste time trying to patch things up. The only permanent solution is to hack open the wall to reveal the root cause of it.

There is no wasting time. To tighten all connections, it less than 10 minutes job. If it works, ts save about 1k and messy work.

Yellow PTFE tape better IMO.
Use the 0.2mm type like this
https://shopee.com.my/-1-PCS-BRAND-TAICO-Wh...7163.7606054192

https://shopee.com.my/VEE-100-PTFE-Thread-S...1847.4449235776

CSM got sell the yellow one pretty cheap at the PJ 225 outlet. This one also can use altho 0.09mm
https://shopee.com.my/12mm-x-0.09mm-x-8m-SE...1900.2727553247

The cheapo white one too thin (usually 0.075mm) and not tough enough to tahan tightening force before ripping

This post has been edited by ceo684: Jun 1 2021, 05:10 PM