Figuring out the best way to plumb a double kitchen sink can be an intimidating process for a DIYer. With the added sink, the potential for problems and leaks only doubles. However, this task is a feasible one for most intermediate DIY enthusiasts.
All you must do is go into the project with enough knowledge, tools, and patience. And with the reward of more culinary capabilities, the project is well worth the time.
You’ll need to have all the tools and parts for this job before you get going. Some hardware stores may offer a double sink installation kit, though those generally just offer an element of convenience. Make sure you have these tools and parts before you begin:
- PVC Pipe Cutter
- Caulking Gun
- Channel Locks
- Sink Drain and Strainer Basket
- PVC Pipes
- Compression Nuts
- Double Sink
- Plumber’s Putty or Silicone Caulk
- Sanitary Tee
- Silicone Sealant or Teflon Tape
With everything you’ll need ready to go, you can begin the double sink installation process. Make sure you have someone on hand to help when needed, and you may also want something cushioned to kneel on while you’re ducked under the sink (like kneepads). If you really want to feel like you work for a professional plumbing company, you can wear your pants a little lower to blend in with the rest of the pros!
Measure your counter and sink to ensure a good fit. If you’re adding a double sink to replace a regular sink, you’ll likely need to cut a second hole into your counter. For this hole, keep in mind that the basin of the sink should sink through the hole but not the lip of the sink. The lip braces the sink against the cambria countertop and supports the weight of the sink. This allotment of space is required for both under-mount sinks and drop-in sinks.
The water running to your sink will also need to be shut off. If there aren’t individual hot and cold knobs you can crank to stop water at the site, you’ll have to turn off your main water valve and drain the pipes.
Once you’ve prepped, measured, and halted water flow, you’re free to move on to the next steps.
Install sink strainers in both basins. You can do this while the sink is detached from the counter, which is easier, or install them after you’ve lowered the sink. Either option will accomplish the same goal. Once the drain and strainer baskets are popped in and set with silicone caulk or plumber’s putty, it’s time to put the sink in.
There are two different styles of sinks, and depending on which one you have, your installation process will vary. Drop-in sinks have a wider lip to allow the sink to sit on the counter while the basin dips into the pre-cut hole. Undermounted sinks don’t have this lip, and they are instead clamped, glued, and screwed into place beneath the counter. If you have an under-mount sink, you’ll need to enlist the help of a friend to hold the sink while you secure it in place.
Before the project can go any further, check to make sure that the drain outlet pipe at the back of the wall is at a good height. You want it high enough for your P-trap to sit properly and do its job while being low enough to allow space for your tailpieces and sanitary tees. Use a tape measure and check that you’ll have the necessary room and height proportions. Comparing these measurements to your pipe measurements can help you come to a conclusion. If the height of the outlet pipe is off, you’ll need the help of a plumber to reconnect it to the mainline behind the wall.
With your pipe zone measured and ready to go, you’ll then attach your two drain tailpieces. These pipes connect the drains to the sanitary tees. Depending on the configuration of your outlet pipe, the length of these pipes may differ slightly in length. Trim off the excess pipe with a hacksaw or PVC pipe cutter. At the connection points on the drain baskets, use compression nuts. Make sure to not overtighten the nuts, as this can cause cracking in the PVC.
The pipe configuration here depends on your installation preference and the space limitations you might have. Your two tailpieces can connect with two 90-degree sanitary fittings and two pieces of PVC, meeting at the sanitary tee in the middle. This configuration looks a bit like a Y, with two lines meeting in the middle to become one.
You can also connect a sanitary tee directly to one drain’s tailpiece. In this configuration, one side runs straight down while the other must bend to connect to the sanitary tee. The bend on the second side is formed by a 90-degree sanitary fitting connected to the tailpiece. A piece of PVC pipe will run from this fitting to the sanitary tee. All meeting points in each configuration are joined by compression nuts.
It’s recommended to first form these connections without attaching anything. You’ll get an idea of how the final piping will look and find any issues before it gets twisted into place.
The finish line is just up ahead. Now, you need to install the drain trap, used to collect a small amount of water and prevent bad odors from rising up to your sink. For this installation, you need a U-shaped trap and a J-shaped trap. Your U-trap connects to the sanitary tee, while the J-trap is responsible for ferrying water to the drain outlet pipe.
To begin, connect the U-trap to your sanitary tee with a compression nut. The hooked part of the J-trap then connects to the U-trap. With those two connected, line up the straight end of the J-trap to the drain outlet pipe and connect.
For this step, you’ll need to thread down the hot and cold water lines through the counter and the faucet’s mounting bracket. With those slipped under the counter, you’ll tighten the nuts of the mounting bracket to secure the faucet to the counter.
Grab the hot and cold water lines under your sink and attach them to the matching lines from your faucet–hot to hot, cold to cold. In most cases, you can easily thread the lines together, but if they seem loose, you’ll want to tighten them with channel locks.
Open the valves of your hot and cold lines first, allowing water to re-fill the pipes. If you don’t have individual valves, turn your main water line back on. Once the water has returned, run your faucet to release air.
Let the water run into the sink, then check for leaks.
Examine every part and element, like the sink lip on the counter, the P-trap, drain tailpieces, etcetera. A thorough search for leaks can help you save money and time down the road, and give you peace of mind in your beautiful home.
If you’re leak-free, congratulations! You’ve just plumbed a double kitchen sink!