Have the original design checked
Ask the installer to compare the completed route with the exact indoor unit's instructions. Have them document its slope, support, connections, outlet, and any concealed sections they need to inspect. Ask whether the head's mounting and water collection area are correct. The fact that suction releases water is useful evidence, but it does not identify the cause by itself.
Blueridge's S2-series installation manual includes drain routing and an installer water-flow check. It is an illustration for the named S2 models, not authority to apply their dimensions to another unit. Blueridge S2 installation/owner manual, OMS2-01, updated June 12, 2024.
Decide whether a pump is justified
We would prefer a properly supported gravity solution if the exact equipment and route allow it. If the installer shows that the approved location requires a pump, ask for the pump model, mounting and access, discharge route, operating sound, maintenance needs, and what protection applies if it fails. Request the revised design before accepting the added part.
Also settle the responsibility. Was a pump included in the original design? Is this a change you requested, correction of the installed work, or an additional scope item? Ask the installer to explain the reason and any charge under your written agreement. Do not assume a new installation problem automatically creates free coverage, but do not approve a new charge without understanding it.
Before closing the correction, request a completed drainage test, confirmation that connections remain dry, and the written result. If the explanation remains unclear, an independent qualified ductless technician can assess the installed route and the proposed fix.
Your next step: Request the original drainage design, the finding that explains the failure, and a written correction plan. Choose the pump only after its purpose and future care are clear.