I am installing a new bathroom sink and it is leaking in two parts, at the faucet drain and at the p-trap. I will ask separate questions for each of these as I believe it is a different solution at both sites (where its leaking). This is all 1 1/4" plumbing. Here I will ask about the faucet drain leak.

The installation looks like this:

entire install

The faucet I am using is a Pfister Ladera Spot Defense and a video for proper installation is here.

The instructions for installing the faucet drain are here:


As you can see, the instructions want you to:

  1. Place the drain in the sink, so that its tailpiece is descending down into the vanity below the sink; then
  2. Thread the conical washer over the tailpiece into place right up against the bottom of the sink, pointing "up" (smaller end of the conical washer facing upwards); then
  3. Thread the flat washer into place, just below the conical washer; then
  4. Screw the thick black nut into place firmly, just below the flat washer, and effectively binding the faucet drain to the sink

This is how I installed it, and it is leaking with this configuration:

enter image description here

One important thing to note is that the YouTube video does not show the flat washer being used at all!

I have made sure everything is tightly fit/snug. Can anyone spot why its leaking, if I'm installing it incorrectly, or whether I'm using the flat washer incorrectly?

  • 1
    Not sure I would trust any drain that instructed you not to use plumbers putty, but then maybe I'm just old skool.
    – Glen Yates
    Sep 21, 2022 at 14:32
  • 1
    5B mentions a seal that goes on top. Did you have/use it? Your picture does not show it.
    – crip659
    Sep 21, 2022 at 14:34
  • The "seal" they are showing in 5B is a plastic ring that is a part of the drain itself. This drain is a push button drain that you toggle on/off by pushing it in/out. You can see it in the bottom photo above. Sep 21, 2022 at 15:01
  • 1
    I'd say it's leaking because all the parts are in the sink, not installed in the drain. :D
    – FreeMan
    Sep 22, 2022 at 14:52

2 Answers 2


Your process is correct, however many of the new plumbing fixtures do not recommend using plumbers putty on the top flange of the drain. These are known as leaking drains. The gaskets that are supplied, (even the soft rubbery ones) often do not seal all the uneven edges of a sink drain hole. Both the glazed top and the rough underside often have enough little variations, nooks and crannies that you cannot get a good seal. I always use plumbers putty to seal the top flange of the tailpiece and use a sealer paste with Teflon, like Great white, to seal the gasket to the underside. That has often fixed leaks. I also like to put a little the Great White paste on the threads of the ptrap too.


Although @RMDman gave a really amazing answer, I went back and watched the video very closely. The printed instructions are wrong (!!!). You are supposed to thread the flat washer on first, cinch it all the way up to the flat black plastic ring toward the top of the tailpiece, and then feed the tailpiece + flat washer through the top of the sink. So that under the sink, you only put the conical washer on (from underneath) and secure it via the nut.

In this configuration, the leaking stops completely. But RMDman gave some solid advice that should not be discredited in any way.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.