3 inch type b/type l adapter for metal chimney

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Old 11-13-16, 11:15 AM
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3 inch type b/type l adapter for metal chimney

I'm now working on fabricating the Type B or Type L venting for my new water heater. I had to have Home Depot pick up the damaged water heater they sold me and the replacement is on the way. I'm going to use 3 inch vent pipe and I'll probably go with the Type L because of the stainless steel inner wall and the higher temperature rating. I assume that if Type B is acceptable for natural gas water heaters then Type L will also be acceptable. I can find nothing in the codes that prevent me from using Type L instead of Type B. I believe that Type L is used mostly for pellet stoves but it certainly should be acceptable for a natural gas water heater. The replacement water heater is the same model as the damaged one I returned, which is a Rheem Performance Platinum 50 gallon short 12 year 40,000 BTU Energy Star natural gas water heater, model# XG50S12DM40U0. It should arrive in appx. two weeks.

As far as the Type L vent pipe goes I haven't decided yet whether I'll use rigid, flexible or a combination of both. The problem I have is attaching to the existing double wall metal chimney. Previously, the metal chimney was used to vent a furnace that was installed in 1971 and my existing 45 year old Rheem water heater. I had a new Carrier Infinity high efficiency furnace and AC installed two years ago, at which time the Carrier installer removed the old furnace vent from the metal chimney since the new Carrier furnace uses direct venting, leaving my existing natural gas water heater the only appliance venting through the metal chimney.

My problem involves attaching a 3 inch Type L vent to the metal chimney. I can't find any adapter that will attach to my metal chimney, which has a 7 inch diameter as measured at the bottom of the chimney. I can't find any adapter to fit a 7 inch metal chimney and I can't find any listings for a 7 inch metal chimney other than Duratech and again, I don't know whether my metal chimney is actually considered a 7 inch chimney or a 6 inch chimney. Is my 7 inch metal chimney actually a 6 inch metal chimney, with the 7 inch measurement being the outer wall of a 6 inch inner wall chimney? Please excuse my ignorance.

I have attached photos showing the current 3 inch single wall vent pipe attached to the metal chimney. I don't want any single wall vent pipe anywhere between the water heater draft hood and the metal chimney. Does anyone know of any adapters that will allow me to connect the 3 inch Type L vent pipe to the side or bottom of an adapter (is a connection to the bottom of the metal chimney even allowed?) that will slide into the 7 inch diameter bottom of the metal chimney I have?

Is one brand better than the other brands of Type L vent pipe? I've been looking at Selkirk, Amerivent, Duravent and Metalbest. I think Metalbest is produced by Selkirk.

Thank you in advance for your time and any assistance provided.

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Old 11-13-16, 09:49 PM
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Name:  Double Wall Metal Chimney.jpg
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Size:  30.7 KBEDIT: While sitting here looking online for an adapter I had a sudden bout of common sense and decided to nail down just what kind of metal chimney I have. I removed the plate off the bottom of the chimney insert and measured the diameter. This diameter is appx. 7 inches. I also measured the circumference, which is 56.2 centimeters, and converted this to a diameter of appx. 7 inches. Sixteen inches from the bottom of the chimney there is an outer wall. I measured the circumference, which is 61.2 centimeters, which converts to a diameter of appx. 7.7 inches. With the bottom plate off I looked up inside the chimney and there were no additional walls so this appears to be a double wall chimney.

Is anyone familiar with this type and size of metal chimney and do you know where I can get a T or Y adapter for it that will accomodate a 3 inch Type L vent pipe? It's not a 6 inch double wall chimney. Is it considered an 8 inch double wall chimney? I can't find any references to a 7 inch double wall chimney online. I've spent days online looking for one and hours in forums to no avail.

Thank you in advance for your time and any assistance provided.
 
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