Hello everyone,

I need an advice. I have a 3-story house with a chimney in such a terrible shape, so the best way is just to get rid of it. However, there are three water heaters and a gas boiler, which are venting into the chimney and which are located in the basement.

My plan is to install a vent pipe in the basement with a direct vent, to which I'll connect both boiler and water heaters, and demolish a chimney.

Does anyone have any experience in this area? Would you suggest a particular vent? Are there any potential noise issues with such a vent? Should I put a vent through existing basement window, or should I drill a hole in the basement wall?

Thank you very much in advance!

You are going to have problems. First of all, in most cases you shouldn't have more than one combustion unit using a flue. It sounds like you have 4. If it actually worked as you describe it, it probably was on account of the height of the chimney creating a lot of draft. If you go with a vent pipe out through the wall, there will be very little stack effect, so you will need draft inducers on each of the units, and each one will require it's own vent pipe. As to through the wall or window, there are very specific guidelines in the gas heat code that will tell you what you can and can't do. Unfortunately I don't have my code books at hand, but you probably could find it on the web somewhere.

Get a professional. I know good mechanics that wouldn't want to touch that one. The only thing that would change my recommendation is if you would have a condensing furnace and water heaters.

Is that masonry chimney ? Or is it framed chimney with individual double wall type "B" gas vents - one for each gas appliance - running through this framed chimney box all the way to the roof?

To do this legally , all of your appliences must be side vent. If they aren't, don't even try it. If your chimney is large enough, I would recommend using individual chimney liners for each appliance.

If you vent 4 gas appliances directly into masonry chimney than you are putting occupants of the house, including yourself, in great danger. This statement is especially magnified if you live in area where it gets cold.

Each gas appliance has to have its own, type "B" double wall gas vent, and has to vent independently. Discharge of each vent has to meet minimum clearance requirements from windows, doors, and other operable openings as well as developed height to assure positive draft.

You can combine regular double wall gas vents into single double wall vent. In this situation you have to know your BTU's load and size the main common vent accordingly.

However, you cannot combine Double Wall Direct Vents. Regular double wall type "B" gas vent and Double Wall Direct Vent operate on two completely different principles:

Regular double wall vent protects hot fumes from cooling down before they reach discharge cap to prevent loss of lift.

Double Wall Direct Vent consists of two isolated pipes inserted into each other. The inner pipe discharges fumes and outer pipe delivers fresh oxygen to the unit. Both, suction and discharge are powered by fan.

Double Wall Direct Venting systems have its limitations as well. You have to carefully plan where you want to place your gas appliances so you don't exceed maximum horizontal vent run as well as number of vent 90 ells. Exterior discharge cap is unique in design and has to meet prescribed clearances as well. Double Wall Direct Vents are usually designed and supplied by the same manufacturer that manufactures the gas appliance that requires direct venting. These vents are not interchangeable with other brands.

I hope you will correct this Code violation whether you take down your old chimney or not. In the interim, I would strongly suggest that you install Carbon Monoxide alarm in your house. They can be purchased at Home Depot or Lowe's.

Let us know if you need any additional info... Milo