For the neutral water clusters, we have consistently shown that the db-MBE(2) outperforms the conventional eb-MBE(3), i.e., the convergence of the MBE can be accelerated by one order. The db-MBE( ) is generally able to reduce the error compared to a full, supermolecular CCSD(T) treatment below the threshold of chemical accuracy (4 kJ/mol).