Does iphone x battery replacement void water proofing seal?

Not if Apple or an AASP does it. Any official service will require replacing the seal.

In some countries or areas, the only service provided as a complete replacement. Replacement devices are made or reconditioned to factory water resistance standards.

sheeraz149 wrote:

Ahk, it is water resistant, i need to replace the battery as it appears a 82% of battery health, so a question in my mind came to know

It may or may not keep water out. We hear the horror stories, but likely it works most of the time. Apple makes no guarantees, and we hear the complaints that Apple “doesn’t back up its claims”.

Not sure if 82% is sufficient. Apple was replacing batteries on demand, but more recently they seem to require (as they previously did) that the Battery Health reading be under 80%.

Keep in mind that the phone is NOT waterproof. It is water resistant.

You should NEVER intentionally expose it to liquid.