Accelerates the degradation of transcripts by removing pyrophosphate from the 5'-end of triphosphorylated RNA, leading to a more labile monophosphorylated state that can stimulate subsequent ribonuclease cleavage (By similarity). Preferentially hydrolyzes diadenosine penta-phosphate with ATP as one of the reaction products. Also able to hydrolyze diadenosine hexa-phosphate and diguanosine penta-phosphate. Has little or no activity on diadenosine tetra- and tri-phosphate, on diguanosine tetra- and tri-phosphate, on GDP-mannose, ADP-ribose, NADH and NAD(+). Manganese cannot be used. Optimum pH is 8.5. Monomer. Belongs to the Nudix hydrolase family. RppH subfamily.