Drain Installation for New Kitchen

I finally am making some progress in my disaster-of-a-kitchen. In the last update I was still trying to get a spot for the plumbing to penetrate the floor and connect to the drain in the basement and the hot and cold water lines. In the last couple of weeks I was able to come up with a plan of attack. I ended up spacing out the floor cabinets away from the wall by 3 inches so that I could sneak the pipes behind them. With a hole now in the wood floor I was able to start work on the drain for the kitchen sink. Most modern drains are 1 and 1/2 inches in PVC, I have seen in older homes drains that are 1 and 1/4th inches but this is no longer the standard pipe size. Please keep in mind that the volume of water that a drain will be able to handle is directly related to the size of the pipe. This is why in showers, where there is far more volume of water, drains are usually 2 inches and why toilets are at minimum 3 inches. That said – I know enough to be dangerous so I encourage you to consult a professional or do your own independent research.

In my case, the drain that I had to tap into was in the basement so my plan was to run a PVC drain line from the location in the Kitchen, along the wall, through the floor, and along the joists. I did not have a chance


But Wait, What Does Vented Mean?

When we talk about a vent, or a line of drains being vented, we are talking about the top most opening in the drain lines. Think of a straw. When you put the straw in water and place your finger over the opening on the top, it creates a vacuum that prevents the water inside the straw from falling out of the bottom. This is the same effect that will happen with a drain stack (stack = the system of pipes). So, in order for drains to let the water flow freely through they are routed through the roof and left open at the top. Below is what this looks like on most roofs:

drain vent on roof
drain vent on roof


Without this component, a vacuum would get created and prevent the water from draining out properly which can cause shower backups or slow draining sinks. If you cannot plumb new drains into the existing system, you must create a vent on that individual line so that it drains right. The actual sink or plumbing appliance drain must be within 5 feet of this vent for things to work right. If not you might notice things like the sink not draining correctly, or the opposite where the sink will actually siphon out water down the drain which will even pull water out of the trap which will lead to a sewer smell in the home. That said – I was not able to vent this line because of the position of it and this is how the previous homeowners had installed it. It’s a shock it works but after testing the sink it doesn’t have any issues draining. In my case, I tried to pitch the drain line only slightly so that there was room for air in the pipe which helps in preventing a siphon or blockage.


Now, back to the new PVC drain. I ended up taking my time and I used 2 10 foot pieces of 1 and 1/2 inch PVC, 6 of the rounded 90 degree elbows, and 2 45 degree bends. It was then a matter or carefully cutting and cementing each piece as I went down the line. For PVC, you must use a special purple primer and PVC cement. It’s shockingly easy to work with PVC and from my experience has saved lots of time and effort on the plumber’s part.


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