Venting an oil-fired water heater

I’m not an inspector, but I want to make sure this is done right, so I’m asking here. I hope you all don’t mind.

I have a brand new oil fired Bock hot water heater (50 gal) with a Carlin burner. It sits about 3 feet from the opening to the chimney flue in the basement. There used to be a 50 year old oil-fired boiler serving a steam heat system there, vented to the same opening (8"). This water heater will be serving my new radiant floor system (I have done all the plumbing myself). There is also a gas water heater for DHW sitting right next to it, vented separately (and higher) into the chimney via a 4" pipe–single wall galvanized (though I was at Home Depot and saw the type B vent pipes–much more substantial). I did not originally install the gas water heater–a plumber did.

I have two main concerns:

  1. What, exactly, should the vent be going from the water heater to the chimney opening? i.e, should it be a special type of double-wall insulated vent pipe? Or just the regular old single wall galvanized pipe you get at Home Depot? I actually really just want to hire someone who knows what they are doing to come and vent it and adjust it. The problem is that since I did the installation myself, none of the oil people are interested in coming out to do that. Their service all goes along with becoming an oil customer. Should I try someone other than an oil burner service person?

I ask because I spoke with two oil service people–one who is associated with my oil supplier, but who came out and was completely clueless about the unit (he actually thought the water heater was broken and needed to be replaced and had no idea how to vent it). The other person seemed more on the ball, but did not come out because he did not sell me the equipment or the oil, and he did not have any interest in being paid for a service call. This guy did say that the pipe to the chimney was just single-wall galvanized with a tee and a damper.

My understanding, however, (from the manual) is the following:
“Using “L” or “A” type venting, connect the heater to the chimney. Do not reduce the smoke pipe diameter;use the same size smoke pipe as the heater flue pipe. Run a separate connector from the heater to the chimney where possible. If the heater must be joined to another oil appliance breaching before going into the chimney, enlarge the existing breaching to accommodate the extra volume of gases from the heater. The entrance into the breaching should be at a 45 degree angle.”

It says to install a damper only if necessary. Also what is L or A type venting? Can someone clarify this? Where can I get all the parts I need to do this right?

  1. My second concern is with regard to the gas water heater sitting right next to it. The gas supply pipe comes down from the ceiling to the left side of the water heater. The vent pipe from the oil-fired water heater will run fairly close to that gas supply pipe (maybe 4"). Is that too close?

I hope I’m just being paranoid, but I don’t want to blow the house up.


Most of the answers to your questions are here on this web site (I think it is appropriate for your brand), although it may not be your specific model…

The type L vent is double walled and is made for use with oil burning units.

As for Type A:

You do not want to reduce the diameter of the smoke pipe as that will cause restricted air flow and possible backflow of exhaust gasses.

It is OK to join the smoke pipe of the water heater to teh furnace smoke pipe (for example) as long as you use the proper connectors as instructed.

For my home, I had a heating professional do the work - he repairs and cleans oil heaters almost exclusively. Even oil supply companies (at least around here) will do the job with out a service contract, they just charge you more.

Anyone familiar with oil furnaces should be able to help you. And they will have the appropriate parts for the job (if they are good tradesmen).

I also do not know the clearance requirements with relation to the gas line, but you can check the side clearance requirements for the oil buring unit and use that as a guide. This should give you the distance flammable materials needs to be placed away from the heater.

I hope this was helpful. I am not an installer, and a good heating professional or oil tech might have better infor for you…call around.

Get a couple of CO detectors for your house.

Thank you for your help. The CO detectors were the first thing I put in. I’m paranoid about burning the place down and suffocating (not necessarily in that order) and maybe causing an explosion, too. At any rate, I know what to do now.

I went around Brooklyn trying to find type L vents at various plumbing and HVAC places. It has to be special ordered. I asked a sheet metal vent fabricator about it and he said that people use it for wood stoves, not oil furnaces. He said that in his house, he just has the plain single wall galvanized steel going to the chimney from his oil boiler, but then the chimney has the proper double-wall vent in it. Since he was the third person to tell me this, I went ahead and used the galvanized that I had bought at Home Depot, with an extra piece to shield the gas line.

All went well and the gas line never got hot at all (nor did the piece I was using to shield it), but I do not like how hot the single wall pipe got, so I’m still uncomfortable with it.

So, in doing home inspections, do you really see type L venting going from the oil burners / oil water heaters to the chimney?

I will call the water heater manufacturer for recommendations on this.

It also seems that oil-fired water heaters are pretty rare. This surprised me. Maybe up in Boston there’s more of them?