The crystal structure of the title compound, {[Cu(C(4)H(4)O(6))(C(2)H(6)N(4)O(2))]·4H(2)O}(n), contains the central Cu(II) cation in a distorted octahedral coordination, symmetrically chelated by the two imine N atoms of a neutral oxamide dioxime (H(2)oxado) ligand [Cu-N = 1.9829 (16) Å] and unsymmetrically bis-chelated by two halves of the L-(+)-tartrate(2-) (tart) ligands, each half being linked to the Cu(II) cation via the deprotonated carboxylate group and protonated hydroxy group [Cu-O = 1.9356 (14) and 2.4674 (13) Å, respectively]. The extended asymmetric unit is defined by twofold axes, one passing through the Cu(II) cation and the centre of the oxamide dioxime (H(2)oxado) ligand and the another two (symmetry related) bisecting the central C-C bonds of the tartrate ions. The structure is chiral, consisting of enantiomeric linear-chain polymers oriented along [001], with virtual monomeric {Cu(tart(0.5))(2)(H(2)oxado)} repeat units and with the chains interleaved face-to-face into `twin pillars'. Nanochannels exist, running parallel to the c axis and bisecting a and b, which host `double strings' of solvent water molecules. Extensive hydrogen bonding (O-H···O and N-H···O) between the chains and solvent water molecules, together with extended π-σ interactions, consolidate the bulk crystal structure.