leakplumbing
Recently, the bottom of our bathroom sink has started to leak just slightly. Little drips come out of the nuts. The leaking part seems to be more toward the end where the pipe meets the wall and the end of the curve where the p trap ends.
What are some common issues with a leaking p trap under the sink?
For inexperienced DIYers; or any body not really comfortable with plumbing in general, the easiest option is to replace the whole faucet. While the faucet may be serviceable, stuck screws/bolts, proprietary disassembly steps, and difficulty finding replacement parts, make this a frustrating job for beginners.
The new faucet should come with instructions on how to install it, but here are the basic generic steps to remove the old faucet and install the new one.
Look under the sink, and you'll (hopefully) see something like this.
Actually, you'll see two. One for the cold water, and one for the hot. Turn the knob until the valve is shut. Then turn the faucet on all the way, just to make sure the valves are fully closed.
If you do not have valves under the sink; or the valves do not stop the flow of water, you'll have to shut the water off using another valve down the line or the main shutoff valve.
Attached to each of the shut off valves, there should be a hose like this.
In some cases a rigid or flexible copper pipe will be used as a supply line, instead of a flexible braided supply line.
Using a pipe wrench or tongue and groove pliers, disconnect these pipes from the valves.
Make sure you have a small bucket under the connection, to catch the water that comes out of the pipe. A small amount of water is normal, it's just the water that was left in the pipe between the shutoff and the faucet. If the water continues to flow or comes out under pressure, tighten the connection back up. This means the valve is not working or has not been fully shut off.
If you follow the supply lines (the pipes you just disconnected) up, you'll find the tailpiece (a long threaded pipe) with the mounting nuts at the top against the underside of the sink. There may be two (one where each supply line connects), or just one in the middle depending on the faucet make and model.
A basin wrench makes removing these nuts much easier.
On some faucets, the supply lines are part of the faucet and cannot be disconnected. In this case the mounting nut may or may not be right at the end of the supply lines.
Once the nuts are removed and the supply lines are disconnected from the faucet (if applicable), the faucet should just lift away from the sink.
Once the faucet is removed, scrape any old plumbers putty from the top of the sink using a 1" putty knife
Now that you have the old faucet removed, it's time to install the new one. Follow the instructions included with the new faucet, or these generic steps.
Grab some plumbers putty, and roll it into a "rope" (about 1/2" or so around) in your hands. place the putty rope either on the sink where the faucet will sit, or around the bottom of the faucet itself. The plumbers putty prevents any water that may be near the base of the faucet, from leaking down into the cabinet below the sink.
Do not use plumbers putty on natural stone (granite, marble, etc.) counter tops, use a bead of 100% silicone caulk instead.
Carefully put the faucet in place, and press it straight down (don't worry if some of the putty squeezes out, that's normal). If the faucet does not stand on it's own, get a helper to hold it for you. Go back under the sink, and install and tighten the mounting nut(s) on to the tailpiece(s) using the basin wrench again.
Remove any excess putty that squeezes out from around the faucet base.
If the old supply lines are still in good condition, you can reuse them. Otherwise, head to the hardware store and pick up new ones (if not included with the new faucet). Make sure to take the old supply lines with you, so you get the right ones.
Using the basin wrench again, connect the supply lines to the threaded tailpiece(s) on the faucet.
Connect the other end of the supply lines to the shutoff valves, making sure to connect the proper line to each shutoff (you don't want hot water coming out when you turn the faucet to cold).
Slowly turn the shutoff valves back on, and watch carefully for any leakage. If you see a leak, turn the valve off and tighten the connection where the leak is.
Turn the faucet on (testing both hot and cold), and look for any leaks.
Use PTFE thread seal tape on all threaded pipe connections, to reduce the chance of leaks.
If any of the threaded connections are difficult to remove (when removing the old sink), soak the connection in penetrating oil.
No, there should not ever be two traps on a single drain line.
The point of the trap is to create a water barrier which prevents sewer gasses from coming up the empty pipe and into the house.
When you have two traps on the same line, you end up creating a kind of vapor block in the line which prevents it from draining properly.
What do you do?
Get yourself some 1 1/2" PVC (not CPVC, which is yellow, PVC which is white) with a 90 deg elbow, and also get two Fernco couplings (black plastic couplings with straps on each end that can be tightened) that will fit the pvc and iron drain pipe.
Use a metal blade on a sawz-all and cut out the p-trap in your basement. (Have a bucket handy!) Leave room to connect the Fernco coupling on both sides. I'd cut the right hand side out just past the coupling.
Measure and cut the PVC so that with the 90 elbow the ends line up with the newly cut drain lines. Glue the PVC together and confirm the fit, then connect to the old drains with the Fernco.
Viola - a proper drain line that will drain smoothly w/ no vapor lock.
Best Answer
If it is a PVC compression fitting, put a bucket under the p-trap and take the trap off.
Odds are good that you will find one of two things. Either the threads were cross threaded, which will affect the pressure seal around the pipe, or the plastic o-ring was caught in the threads at one point in time and was mangled. A mangled o-ring won't provide a satisfactory seal.
Either way you will know which part to replace, and these connections (provided it is compression fitting PVC) can be replaced easily at your local hardware store.
If it seems that everything is fine, look for the following items:
Is the pipe being unnaturally flexed or bent due to particular pipes being too long or short? If so the solution is shorter / longer pipes, but make sure you don't dramatically change the geometry of your setup.
Are the locking nuts really tightened appropriately? Sometimes a good "extra twist" solves a leak in the best possible way. Remember, if you "break" an obviously replaceable section of pipe, you're out a few dollars in plastic, so don't be shy.
The joint between the end of the p-trap and the pipe from the wall is supposed to be constantly under water, so it is fairly common for those to leak. Normally they are fitted and tested for leaks. The workman will not leave with one leaking. Since it is under the sink, and people often store items under their sink, eventually the pipe gets bumped. That's probably the source of your new dripping; however, it is highly unlikely that anyone will remember bumping the pipe, even if they did it.