In a commercial lease, the owner of the property is typically responsible for the plumbing. However, if the tenant wants to make any changes or modifications to the plumbing, they may need to get written approval from the owner. This is because the pipes and other infrastructure necessary for water delivery are typically considered part of the building, not specific to one or more businesses within it. If something goes wrong with the plumbing, it’s up to the owner to fix it.
Tenants are sometimes allowed to make minor alterations, like putting in a new sink or clearing blocked drains, however, it’s best to contact the landlord prior to starting any commercial plumbing works.