Hi, I am putting plumbing from my house sewer and water connecting it there. And running it too a garage 25 feet away to a loft upstairs which will have a full bathroom and kitchen. I live in winnipeg so winter gets cold I'm digging a 7 foot down trench. My question is what size of pipes and what kind of pipes do I need to run in and out of the trench for sewer and water?

Are you permitted to do this work, you should get a professional to do it

Yes, the town should be involved for permits to allow it.

Hello Dylan,

for Sewer, you should install 3" main sewer, 3" pipe for the toilet, 2" for tub and / or shower and 1 1/2" for sink. Slope should be 1/4" per foot for all sizes. You can use one 2" vent at the roof level to vent all plumbing fixtures in your new bath.

As far as water goes - it depends how much pressure you have at the point of connection into original water line. If low pressure ( under 35 PSI ), bring 1" line all the way to the toilet than distribute with 1/2" dedicated branches from that point on. If high pressure, install 3/4" as a main run all the way to the toilet, than distribute with 1/2" dedicated runs to the sink and shower.

Insulate pipes as per local Code. As far as depth of the trench goes - your pipes should be installed below freezing line. This info varies with geo-location and can be easily obtained from your Building Dept. prior to excavation.

You may consider installing a small hot water heater, just for your new bathroom. Running hot water line from the main house and under ground may by energy inefficient. In other words, it will take too long for hot water to arrive at your new bathroom.

Good luck with your project

Milo

Everything you ask is going to be dependent on the plumbing code being used in your state. Certainly a plumbing permit is required to do the work, but then, so is a building and electrical permit so I will assume that you have that covered... ;)

In terms of your questions, your code may want PVC (white plastic) or ABS (black plastic) pipe for the sewer drain. In some states, 4" is required underground, but 3" can be used in other states. If your area required 4" underground you would run that to the garage and install a 4" cleanout flush to the ground 18" off the garage foundation. Once into the garage, you would run a 4" pipe to the toilet, a 2" pipe for the shower and a 2" pipe for the sink (stub out of wall 1.5").

Trench bedding and bedding substrate/compaction will also be covered by local code. Most codes will NOT allow sewer and water in the same trench, or if the code does allow it, the requirements are very specific, so do be sure to check out the local requirements on this!

Venting will be another issue. Since this garage will have the one bathroom, you will be required to install a 3" vent stack through the roof... all buildings with plumbing require a 3" minimum vent through the roof. You may be able to WET VENT the bathroom group (2" sink drain and vent will "wet vent" the entire bathroom group), or you may need individual vents for all fixtures. Again, specific to your area code, but no matter what type of venting is required all vents will connect into the 3" stack vent.

1" or 3/4" water line in copper tube type K or whatever they require in your area... again, each state/town/county will differ on this requirement so you simply have to ask the local people that know the answers.

As Milo mentioned, installing a water heater at the source is the only way to go here.