I have to run 4" drain pipe for the washer that is on the second floor, but, the building being old and all, I wouldn't want to rip the floors, instead, I was thinking of running the drain on the outside of the house and then go back in at the basement level. It would be preferable as the pipe would be hidden with other exterior pipes and would not look ugly or out of place. This is for state of CT, so to prevent winter freezing, I was told to go with 4" PVC instead of the 3" recommended by washer manual. Any suggestions? Drilling through the floor to run the pipe on the inside is not possible, so, what options do I have?


  • PVC does not do well exposed to sunlight. Are you going to tie this into your sewer or septic system? – Kris Oct 21 '18 at 2:25

I would strongly suggest a "Pipe chase" (box, preferably well insulated) around the pipe on the outside of the house in a freezing climate.

That same box will also help to "improve the appearance" (if the pipe will be "grouped with other outside pipes" as you say they can all be in the box, though I'm frankly puzzled as to what such a group of pipes on the exterior would be in a freezing climate...) and protects the PVC pipe from sunlight.

Whether any single measure (such as oversizing the pipe) or combination of measures will actually "protect from freezing" where you expose a pipe to freezing temperatures is highly dependent on the weather for the day or week, the particular details of the water flow in the pipe, and how they interact. If it freezes more than it thaws, it will eventually build up a plug of ice and be a problem - which is why most folks in cold climates try to avoid having plumbing in the outside walls, much less all the way outside the house.

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    Note that the chase needs to be a) well-insulated from the outside, and b) NOT insulated from the inside. Otherwise, no matter how much insulation you use, it will eventually freeze. – Daniel Griscom Oct 21 '18 at 13:53
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    You're dumping water that's above freezing (sometimes well above freezing) into it. If it's adequately insulated, that will be sufficient heat to keep it clear without requiring removing insulation on the house side, as it's a vertical pipe. – Ecnerwal Oct 21 '18 at 14:55
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    What if there's a running faucet or toilet that causes a slow dribble? You'd get this gradual buildup of ice in the pipe, quite likely eventually blocking it. Then how do you unblock it; wait for warm weather? – Daniel Griscom Oct 21 '18 at 16:47
  • Did you Read the Question? It's specifically a Clothes-Washer Drain line. High volume, short duration, I've never seen one "dribble" - if it did, you'd have a full washer tub inside the house, not a trickle into the drain line.. – Ecnerwal Oct 21 '18 at 20:58
  • I'd still be concerned. I live at most 90 miles north of the OP, and we've had winters where it stayed in the single digits for days on end. It's a risk call; I wouldn't do it. – Daniel Griscom Oct 21 '18 at 21:17

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