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Plumbing New Bathroom

markg11cdn's picture

Our house is missing one Master Bathroom and it is going to be my next project. When I laid new hardwood in the upstairs I left a big hole where the bath is to be installed and it is time to fill that hole with a new bathroom.

I pulled up the 3/4" sub-floor today and confirmed my guess as to what was there. Here's a picture of the area with the sub-floor pulled up and leaning against the wall.

There is insulation because the space underneath this new room is a stamped concrete patio.

There is 1x2 strapping running across the bottom of the floor joists (notched) and aluminum soffit is nailed to the strapping. On top of the insulation is a VB. The floor joists are 2x12s.

First question is can I safely run a 3" drain pipe through the 2x12s? At 1/4" per foot, and a 8' span, it'll leave 3" of wood at the top of the first joist and at the bottom at the last joist. Is it safe to run this vent through the unheated space (I don't really have an alternative). I'm in Southern Ontario and we get regular freezing. Is it okay to run the hot/cold pex supply lines through this space - I'll insulate the pipes with foam rubber.

Looking at my plumbing book, I think I can drain the shower into the stack at the same point as the toilet though I'd need to add a revent before picking up the shower around the corner [Master Bathroom Overview.jpg] (Sketchup file, I left it large for detail).

Since this bathroom is across the house from the others, I'll be adding a new roof vent as well.

Happy Holidays and thanks for any help you can offer.

cheers - mark

[Edit to fix shower/toilet vent description]


Edited 12/28/2007 5:20 pm ET by markg11cdn

(post #105389, reply #1 of 7)

Not sure on specifics, but here's a suggestion, can you switch the bathroom, or the flow of the drains to the right side? Instead of having to drill 3" holes through all your floor joists, run 1½" from the tub to the sink to the toilet, and 3" from there back to the drain. Even if 3" is an acceptable hole, i'd much rather only have a 2" hole.

(post #105389, reply #2 of 7)

Because of the skylights I can't change the location of the shower and keep the skylights. The stack has to stay on the far side near the shower to get into the crawlspace below the house. The room below the other side of the bathroom (under toilet) is on a slab and has a big sliding door, so no way to run the stack across that room.

If the 3" hole is too big I'd probably squeeze the toilet over to beside the shower, but that's less than ideal for us.

cheers - mark

(post #105389, reply #3 of 7)

could you use the the system that grinds up waste and sends it through a 3/4 pipe  saniflow i think it called

(post #105389, reply #4 of 7)

From a plumbing view point  the toilet should set about where the wood cabinet in the picture is, and be the first fitting in the bathroom. Everything else can be on 2 inch pipe with 1/4" per foot fall. The water lines freezing might be a real issue and hard to prevent with out taking the porch ceilimg apart.

(post #105389, reply #5 of 7)

Well of course the toilet should be there. I'm not sure why I didn't put it there in the first place.

Here's a new picture with the toilet moved and what I think is the correct waste/revent line for the vanity. The vanity and toilet are up against an exterior 2x6 wall. It is drywall->vb->FG->OSB->Housewrap->FC siding.

Can I run the vanity waste line and the PEX water lines through the 2x6 exterior wall and not have freezing problems? If that could be a problem I can add a 2x4 wall onto that exterior wall and run the lines through that. Not a big deal to lose the space and I have to put in new drywall either way.

cheers - mark

(post #105389, reply #6 of 7)

The extra 2x4 wall sounds like the safest way to protect the water line. That vented soffit would worry me in a strong cold wind.

(post #105389, reply #7 of 7)

If you go with the added 2x4 wall make sure you run the piping to the inside with insulation on the outside.


Another option is to wrap the pipes in heat trace that is thermostatically controlled.



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