I have a tankless boiler installed indoor for a house renovation job. There is a lot of constraints on where the exhaust pipe can be directed. Right now, it's directed 3 feet away from the house and pointed downward. Structurally, it's not possible to direct it to the roof. From time to time, the exhaust gas may travel (depends on the wind) to the entrance waiting area. It does not smell nice. How to best re-direct the exhaust to prevent such air travel? Thank you so much for your suggestion and ideas in advance.

  • Photos would be useful.
    – herb guy
    Commented Feb 23, 2018 at 4:17
  • Why is rooftop not an option? It's the 'correct' solution. After that - you are better off moving the water heater to a different part of the house.
    – virtualxtc
    Commented Feb 23, 2018 at 14:16
  • Why does your tankless unit have a steam exhaust? What exactly is this unit? If it's the regular exhaust from a condensing unit (which can use PVC ducting), then you've got a few code requirements to deal with in keeping exhaust away from intakes and people. This particular situation does not look code legal. However, if this is just steam, you could always make a trap to condense it and let it simply overflow onto the concrete. Please add what type of unit this is.
    – Hari
    Commented Feb 23, 2018 at 23:36
  • Thank you for taking a look at the situation. I have attached a photo of the inside water boiler setup. The boiler is a Triangle Tube Prestige. How do I get a condensing unit (and what product to buy) to convert the steam into water? Would it impact the performance of the boiler in the long run? Thanks in advance!
    – Didi
    Commented Feb 24, 2018 at 18:47
  • Are you concerned about noise, or the water vapor (it's not steam)?
    – Bryce
    Commented Mar 29, 2018 at 7:20

1 Answer 1


The fact that this is PVC (type IV ducting) tells me this should already be a condensing unit, so the amount of steam should already be minimal.

There's nothing stopping you from projecting that pipe further away from your house as long as it doesn't get withing 3 feet of your neighbor.

Based on your interior pictures, I'd recommend just drilling another hole in he side of your house closer to where your unit (which is generally the preferred way to vent the unit), which should move the steam far enough from your house vent based on the pictures you provided.

Else, if you think you are still likely to have issues with the exhaust, you really should move it up to the roof / chimney.

However, as long as you don't obstruct the airflow, you could minimize the steam of the current outside vent by running it into something like a dryer vent bucket: https://www.homedepot.com/p/Everbilt-Indoor-Dryer-Vent-Kit-TDIDVKHD6/203626526

Be aware, that the exhaust from high efficiency water heaters is acidic and will eat away at any metals that might be part of your pail setup.

  • Thanks! I have attached how it's installed on the inside to give more perspective on this. I would like to find out what solution on the outside I can do. It's also not ideal to vent indoor because of the heavy steam. Heads for the heads up on the acidic outlet. You are right. This unit has such an outlet at the bottom and it was eating away the copper and the copper needs to be replaced now.
    – Didi
    Commented Feb 24, 2018 at 18:51
  • 1
    I was definitely NOT recommending venting inside as that will potentially expose you to carbon monoxide. If you are really getting that much steam, I'd guess you have a unit that should be using Catigory III not PVC venting.
    – virtualxtc
    Commented Feb 26, 2018 at 1:26

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.