Easy install customer support was fast and easy. Johnston boiler company manufactures the world’s largest scotch marine firetube boiler we pioneered the first water-backed boiler and continue to lead the industry in innovation today. To find your local vaillant installer. Contact the energy saving advice service on 0300 123 1234 to see if you qualify. We install worcester, bosch group, condensing boilers that have been proven to improve efficiency by 90% which in turn.