Gas fireplace venting from a family-owned team in South Orange

Why horizontal flex vent rises away from the unit

Flexible and rigid pipe follow different installation rules in one maker's manual. Horizontal twist-lock pipe in that manual is laid on a level plane, while horizontal flex has to climb 1 inch for every 24 inches as it leaves the fireplace.

A flex run that sags between supports loses that rise. When we find a sag in a reachable section, our technicians support it again at the right slope and note the change, since the manual's numbers only work if the pipe actually follows them.

Why a B-vent loses its draft

Poor draft has a long list of venting causes in one B-vent fireplace manual, and each one points at a different repair. Our pros work through it in order, since the fix for a short vent is nothing like the fix for a blocked one.

The list below comes from that manual. Several causes can exist on the same house, which is why we check them all before quoting.

• Too much offset or too many elbows
• A vent that is too short or too close to the roof line
• A blockage restricting the pipe
• The wrong vent type or the wrong size
• More than one appliance on one vent

A new fireplace on an old vent

Swapping a gas fireplace for a new one does not mean the vent comes along. The vent system is part of the new unit's listing, and its manual decides which pipe, caps and adapters are allowed.

Our specialists read the new model's venting section, identify the existing pipe and tell you honestly how much of the old run can stay. Sometimes the answer is most of it, sometimes none, and the written estimate shows the reason either way.

Why a missing odor does not prove there is no gas

Natural gas and propane have no smell of their own. One maker's manual explains that an odor-making agent is added to both so people can notice a leak, and it warns that the added odor can fade, so gas may be present even when nothing can be smelled.

That is one reason manuals ask for gas connections to be leak tested after service with a soap solution or an approved leak test spray and never with an open flame. Our technicians test every connection they disturb before leaving.

Nothing but gas in a direct-vent firebox

A gas fireplace is built for one fuel. One direct-vent manual says not to use any solid fuels in it, naming wood, coal, paper and cardboard, and not to use it to cook or burn paper or other objects.

Debris and ash from anything else can block burner ports and air passages and change how the vent works. If our crew finds signs of burned paper or other material in the firebox, we clean it out and explain what it may have done to the burner.