Tiny house plumbing stage one, drain line rough in. There are a lot of rules about plumbing. The first rule for me was getting some professional advise. My sister's friend Steve is a plumber and he knows more than I could have learned on my own. I had researched enough to know the drain lines I was about to rough in needed to slope 1” for every 4'. What I didn't know was how to vent my lines, and the other subtleties of drain line installation (Clean outs, minimizing 90 degree fittings, and the best thing for Tiny house drain lines: a cheater vent- I will save the venting explanation and leave it up to you to research if you feel inclined). I contacted Steve to see if he was interested in consulting for us and he was. Lucky for us!
After our consult with Steve I drew up some mock plumbing drawings of how the drain lines would fit together and incorporate a Waterless Ptrap. Ptraps are devices that stop plumbing gases from leaking out a sink or tub drain. I was a little obsessed about using this type of ptrap because it would fit the drain lines within the clearances of our 2”X6” floor while helping to avoid freezing in the winter.
After our consult with Steve I drew up some mock plumbing drawings of how the drain lines would fit together and incorporate a Waterless Ptrap. Ptraps are devices that stop plumbing gases from leaking out a sink or tub drain. I was a little obsessed about using this type of ptrap because it would fit the drain lines within the clearances of our 2”X6” floor while helping to avoid freezing in the winter.
Long story short. Steve picked version two and I went to find parts: the waterless ptrap, some 1 1⁄2 ABS, and some 1 1⁄4 Sched 40 and all the fittings. The middle two items mentioned are types of plumbing pipe.
First I used our building plans and did some math. I redrew the tub drain location because our tub and trailer are different than the plans.
I attempted to install according to my drawing but found the slope of the pipe would require that I drill holes in the lower 1/3 of our joist. Doing this will compromise the integrity of our floor framing.
Plan B: this is when we raised the tub to allow enough slope while fitting our Schedule 40 1 1/4” drain lines in the floor joists safely. Staying in the middle 1/3 of a joist is a building code thing you may read about if you like.
First I used our building plans and did some math. I redrew the tub drain location because our tub and trailer are different than the plans.
I attempted to install according to my drawing but found the slope of the pipe would require that I drill holes in the lower 1/3 of our joist. Doing this will compromise the integrity of our floor framing.
Plan B: this is when we raised the tub to allow enough slope while fitting our Schedule 40 1 1/4” drain lines in the floor joists safely. Staying in the middle 1/3 of a joist is a building code thing you may read about if you like.
Due to the length of our drain lines I had to reinforce one of the joists. This reinforcement was necessary because I had to drill into the bottom third of the joist. Since I had extra reinforcing material I added it to the other joist to beef it up. These joists will sit right under our fresh water tank and be supporting 300 lbs of water. The reinforcing was precautionary and may not be necessary but it gave me piece of mind.
With all the holes drilled in our joist at the right slope I was then cutting pipe and dry fitting it with all necessary fittings, and cleaning cut ends to test the full assembly and double check the slope before gluing it all. I then moved on to priming and gluing where required, and adding pipe insulation.
Whoops...I didn't test the lines before insulating around the pipes. In lieu of testing prior to insulating, I plugged the end that will empty into our gray water tank and filled the pipes with water. The same amount of water came out after unplugging the pipe a couple of hours later so it should be good. Should is a dirty word. Fingers crossed for non-leaky drain lines.
With all the holes drilled in our joist at the right slope I was then cutting pipe and dry fitting it with all necessary fittings, and cleaning cut ends to test the full assembly and double check the slope before gluing it all. I then moved on to priming and gluing where required, and adding pipe insulation.
Whoops...I didn't test the lines before insulating around the pipes. In lieu of testing prior to insulating, I plugged the end that will empty into our gray water tank and filled the pipes with water. The same amount of water came out after unplugging the pipe a couple of hours later so it should be good. Should is a dirty word. Fingers crossed for non-leaky drain lines.