I have a single story brick house built in 1992 on a slab with the current dryer vent being a 3 inch pvc running thru the slab under a tiny room (garage accessible) that contains my 50 gallon gas hot water heater. Laundry room is internal to the house with one wall bordering the garage. Rough layout is shown below. Dryer (D), washer (W) and gas hot water heater (H).

house layout

Some general info :

  • The gas hot water heater is elevated on a lumber-framed base about 1 or 1 1/2 ft above the slab.
  • The hot water heater vents straight up thru the attic to the roof.
  • The dryer is electric
  • I have a 4in diameter flex dryer vent hose running from dryer down at an angle to the 3in pvc access point
  • Washer and dryer are front-loading
  • Current washer design (and the wife insisting the appliances open away from each other dictate their position (washer door cannot be reversed). This means dryer vents via 4in flexhose at an angle over behind the washer and down to the 3 inch pvc access point in the base of the wall and down into the slab.
  • I realize the vent pipe diameter should be 4 inches, pipe should have minimal number of angles plus having it in the slab is not a good choice for several reasons (condensed moisture accumulation, etc...). Maybe 3in was ok back when the house was built but its not today (back-pressure due to pvc accumulating lint per the moisture in the pipe plus I'm pretty sure 3in is not code-compliant) and trying to translate from 4 to 3 is causing its own problems.
  • The wall next to the dryer with the pvc slab access is about 6 feet from the exterior of the house.
  • I have hardwood cabinets over the washer and dryer in the laundry room. Length from ground to bottom of the cabinets is 57 inches.
  • Length from ground to top of the hot water heater is 75 inches.

Question - What is my best option for retiring the pvc/slab pipe and re-routing the dryer vent?

I want to go straight out the side of the house with a single 4in metal dryer vent pipe running underneath the hot water heater but is that ok (code-compliant, etc...)? I also thought about routing up thru the wall into the attic and over to one of the soffit vents. I'd rather not route thru the roof (or really to the soffit) because of the angles, having to vent straight up and having lint collect at the exit point or where it angles up if it is too heavy to make it out.

I didnt build the house, I would just appreciate options for fixing this mess. Thanks!

Edit - a photo of the top of the hot water heater for reference enter image description here

  • You should fix that draft hood!
    – jay613
    Feb 8, 2022 at 21:06
  • Thank you yes I will fix this shortly
    – Chris
    Feb 8, 2022 at 21:21

1 Answer 1


Why not over the water heater instead of under? That keeps the vent away from the ground where bugs and dirt are more likely to enter it, and where its heat and lint will damage any plants you have just outside. And the vent pipe is less likely to be stepped on by anyone working on the heater.

100% solid pipe solution, no flex. Out the back of the back of the dryer point the elbow 45 degrees up and to the left, then near the ceiling another 45 degree bend directing it towards the outside, then straight through both walls passing over the heater.

If your dryer has a side venting kit you could add that to the picture, and get back 4 inches of space between the two machines ... I bet your wife would love that. :)

Put a time capsule in the PVC pipe and concrete it up at both ends.

Seal up the hole in the interior wall, around the dryer vent really well and install a CO detector in the laundry room. to ensure that if exhaust from the water heater enters the house you'll know about it.

  • Thanks for your reply. I attached a pohto of the top of the hot water heater. Dryer is just to the right of the heater in the adjoining room. I have cabinets in the laundry over the dryer so I'd need to route in the stud wall (same wall that has the pvc access at the bottom) so I'm not following the 45 degree bends you mention. Maybe you mean for me to vent up in the stud wall and then over in front of the water heater pipe and out the side of the house? This is a possibility, I just want to minimize bends but this might be the answer.
    – Chris
    Feb 8, 2022 at 21:03
  • I think I mis-stated "routing in the stud wall" as its a standard 4in wall with sheetrock. I'd rather pneed to go thru to the water heater side and then up and over but it would be hard not to get in the way of the heater.
    – Chris
    Feb 8, 2022 at 21:08
  • I thought the dryer vent could pass behind the heater flue and pipes but what is that other pipe in the corner? Looks like a downspout.
    – jay613
    Feb 8, 2022 at 21:09
  • What is the height of the top of the heater from the ground, and the bottom of the cabinets from the ground?
    – jay613
    Feb 8, 2022 at 21:11
  • As best I can tell, its just a couple of gutters that come half way down, I assume it is for venting CO.
    – Chris
    Feb 8, 2022 at 21:13

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.