We had a complete new heating system installed in the summer with a Worcester Greenstar R35 HE plus combi condensing boiler. Now the heating is being used regularly we are getting a whistling or water movement sounds from the rads. This is intermittent and travels between the rads - its really noisy. The plumber who installed it says he may not have put in enough inhibitor. As he doesn't seem in a great hurry to come and sort it out, I wonder if the inhibitor is just a guess? Has anyone had the same problem or any ideas please? Thanks