Our company had a call back on a job today that i went back to, turned out to be a faulty 2 port valve, but anyway there were two pumps one for heating one for water. heating pump was fed from p/overun boiler as normal but water pump next to megaflow cylinder was fed from water on signal on clock so pump was running even if cylinder stat wasnt calling for heat. All we did was wire the new boiler up to existing system so wasnt sure if this was done for plumbing reasons as i understand megaflows are sealed systems. Or should the pump have been fed from the pump live on the boiler? thanks guys!Guiness Drink