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Question DetailsAsked on 10/16/2016

Chimney liner installers in Berks co. Pa

Had new high efficiency furnace installed leavin gas hot water heater venting up chimney alone. Was suggested I line the chimney.

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1 Answer


Because the water heater (now by itself) is relatively low discharge volume of exhaust gases, normal chimney flue or liner is too big and does not provide adequate airflow so can cause backdrafting too easy.

You need a Heating and A/C contractor (should have been the one who installed the furnace) to tell you the rated size for the flue. Actually, if you need a smaller flue for the water heater alone (a common issue), usually, for a "gravity" hot water heater putting in a chimney liner is not the way to go - commonly you either use sheet metal ducting like normal double-wall B-vent or stainless flex coil tubing for this (single-wall allowed in some areas if in brick/concrete/masonry chimney). And he should not have installed the furnace - or alernatively should not have left the water heater operational - if the existing chimney is too large for the water heater alone - that is dangerous and against code for him to do that.

Also - if a previously used wood or coal burning chimney thsat they ran the appliance exhaust up into, some areas require that the ducting be stainless steel, to resist the acids from the creosote in the chimney when it get damp - it eats up galvanized relatively quickly in some cases. Other code areas figure double-wall ducting will work OK, others require stabilizers or centralizers on the ducting (finger guides that keep the ducting from toughing the chimney wall).

Depending on how hard the chimney is to get ducting into, fairly frequently (especially with 2-story chimneys with more than one fireplace in it) it is cheaper (especially if water heater is older) to just change it out as well and replace it with a direct-vent high efficiency one also, venting directly out the wall - though that does put another commonly $1500-2000 dent in your wallet right after the several to many thousands for the furnace.

Answered 4 years ago by LCD

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