Sewer/Drain Plumbing

With the footing for the foundation excavated and forms in place, it was time to install the underground drains (DWV - Drain, Waste, Vent) for the new shower, toilet (WC), tub and sink (lav). I opted to do this work myself since the plumbers I talked to wanted thousands of dollars to do the job.

I did hours of research to learn the proper way to make DWV connections that are code compliant. I spent many hours reading plumbing forums, plumbing articles and sketching out how I hoped my system would come together. Then I went to the supply house and grabbed the parts from my list. In all, it took about four different trips to the plumbing supply store to get various things. All DWV parts are ABS plastic.

The parts cost me about $450 which includes some extra pipe I will use later for vents in the walls. Much of the time I spent on this project went toward digging. Jason helped quite a bit with that process. We located the clay sewer line nearly three feet underground. I used a snap tool (rented for $10) to cut the line and I stuffed a rag into the line to keep debris out and sewer gasses in while we worked.


We trenched out the layout for the drain lines and started making connections at the clay pipe using a "fernco" fitting that clamps around the new 4" ABS pipe and the old 4" clay line. A few inches from the ABS to clay connection, I put in a 4" Test Tee which will allow us to easily plug the line later for a pressure test. About a foot up from that, I put in a two-way clean out which extends vertically to a few inches above the ground level. This clean out will allow a roto line to be fed into the system in the event of a clog.

After the two-way clean out (keeping in mind that we are working in reverse of the direction the drain water will flow) I reduced the line to 3" and ran it under where the new concrete footing will be. I used a wye fitting to branch off the main 3" line toward each individual drain. In some cases, the wye fitting included another angle to get the pipe moving in the right direction. I'm not going to get into code requirements here, because there is just too much information to put down. You can see an example of the branch off in the picture below. The main pipe runs through the middle from right to left (further to the right is the clay line and to the left the line runs to the toilet and shower). You can see the lav (sink) drain branching toward the bottom left and the tub drain toward the top right. We made sure all lines had the required 1/4" per foot drop so that the water would flow down stream. We also tediously hard packed dirt under and around the pipes (a process called "shading") to keep the pipes in place and prevent sagging.


Because I'm not a plumber and all the intricacies of properly connecting and venting drain lines is still somewhat of a mystery to me, I decided to vent each fixture individually instead of trying to wet vent anything. A plumber would no doubt have found the way I ran the lines more work than necessary, but I guess that's why they make the big bucks! I verified with some plumbers that the way I designed the system would work, and they said that it would, even though it was complicated. As you can guess, they did NOT tell me how THEY would do it, and I can understand that.

Below, you can see a couple pictures of the shower, WC and tub drains and their vents. I attached a 10 foot mast to the shower drain in order to perform the mandatory water test. For the test, you plug off the main line (in this case, before it drains into the clay line), and stick a hose in the 10 foot mast, filing the system with water. As each opening in a fixture drain and vent overflows, you cap off the line, ending with the mast overflowing, at which point you turn off the water. By doing this, you have filled the entire drain system with water and because you have a 10 foot mast that is also filled, you have created roughly 5 psi of pressure in the system. Once the system was filled, I went around and checked fittings for any leaks. Not finding any, I checked the water level at the top of the mast after about 45 minutes (code requirement here is 15 minutes) and found it to be full.



I left the system filled and the ladder in place for the city building inspector who was scheduled to arrive sometime that day. I received a call from the inspector several hours later. She told me that the drain system passed inspection and she had also passed the footing rebar inspection. Hurray!

That night, I rushed to get the drains wrapped in foam to protect them from the concrete. The concrete crew was set to arrive first thing the next morning to grade the area and the inspector would be back later that same day to do the pre-slab inspection. No time to waste!