Q how much will a replacement boiler cost? Just a note to let you know how much alex helped us his work ethic is great the results of his work are really great he is very knowledgeable plumber and very efficient he's very respectable and good to have helped. Can do will do well done guaranteed! Combi boiler replacements that update old boiler systems may also involve. If you suspect the blockage is on the public wastewater side and you are not connected.