Aquatherm pipes are non-metallic, as are most of the fittings, so no dielectric unions are required. However, if an Aquatherm fitting with metal threads is being connected to a dissimilar metal (e.g. Aquatherm brass to galvanized, or Aquatherm stainless steel to copper), then a dielectric fitting should be used just as it would be for any other dissimilar metal joint connection.