Why You Shouldn’t Use Thread Sealant (Pipe Dope) or Tape on MRCOOL Line Sets

MRCOOL line sets use flare and gasketed fitting., which are designed to create a metal-to-metal seal on the flare surfaces, not on the threads. Because of this, thread sealants like pipe dope or Teflon tape are not only unnecessary—but can actually cause problems.

Why Sealants Are a Bad Idea

🔹 Interferes with the sealing surface
Flare fittings seal when the metal flare face compresses tightly against its mating surface. Adding tape or dope can prevent proper contact, leading to leaks.

🔹 Creates debris in the system
Excess tape or sealant can break loose and enter the refrigeration circuit. This can clog components, restrict refrigerant flow, or cause damage during future servicing.

🔹 Affects torque accuracy
Flare fittings must be tightened to a precise torque. Sealants add thickness to the threads and change how the fitting tightens, making it hard to achieve the correct torque—resulting in leaks or damage.

Bottom line:
Flare and compression fittings are designed to seal on the flare surface—not on the threads. Adding tape or sealant does more harm than good and can compromise system performance.