I'm looking into installing a secondary circulation system, but I can find precious little information or comment about it. Any help, please? Does anyone know where to start looking for a suitable pump? It doesn't need to be capable of much flow (0.5 litres/min ?), but does need to operate under a high static pressure (4 bar - it'll be used with an unvented cylinder). Needs to be bronze (or stainless?), and suitable for potable water.