You can caulk under both with Kitchen and Bath Caulk (retails at Home Depot here for $1.94 + tax per tube.) It comes in clear, white, tan and a few other colors. I recently had to use this product on a bathroom sink, and would like to suggest buying some nitrile or latex gloves at the same time. If it dries on your fingers, it's a pain to clean off. The color dyes will stain your skin.

 

Unless your countertop is marble, use Plumbers Putty under the faucet. The plastic piece is there to prevent leaking water but I always use the putty. It is easier to clean up after installation than caulk. It does have a bad reaction on marble surfaces and can stain it. You should not need anything on the drain pipe except the putty under the drain flange. If you use a caulk or silicone, and ever need to take it apart, you will never do this again.

 

Hello
i'm installing a new faucet in my bathroom.
1) Should I caulk unerneath the baseplate of the faucet? It doesn't have a rubber base, but a plastic one, so I was thinking I should caulk around it?

2) Should I caulk under the drain piece? like the circular donut you put in the drain, which screws in underneath.

1. I wouldn't bother caulking under the faucet. Water dripping under the faucet and onto the floor is much less of a problem than black mold growing on any silicone caulk you have there. If you do decide to caulk, buy the more expensive silicone caulks because they will have more mildewcide in them. Personally, I prefer Dow Corning 786 if it's available in your area. It comes in the only caulking tube I've ever come across that's truly resealable. However, to make it so you need to use a small hose clamp. If you buy any Dow Corning or Dap caulk in a resealable tube with a externally threaded cap on the nozzle, post again and I'll tell you how to reseal them.

2. Yes, It's a good idea to apply silicone caulk:
A) Around the sink hole under where the drain flange will be
B) On top of the rubber gasket that slides up the chrome tail piece to seal the bottom of the sink, and
C) All up and down that chrome tail piece that sticks down out of the sink, including on the threads near the top. The silicone will act like a lubricant allowing you to slide the rubber gasket up the chrome tail piece relatively easily. Without any lubrication between the rubber gasket and the chrome tail piece, it's like fighting with a bear to slide that rubber gasket into place. You don't need a lot of silicone on there, only a thin film to act as a lubricant.

So:
Start by caulking around the hole at the bottom of the sink.
Then, put something on an overturned pail under the sink so that you can drop the tail piece into the sink hole without the drain flange dropping onto that silicone you just put in the sink. Wearing latex gloves, slather up the tail piece (including the threads) with silicone caulk and drop it into the sink hole (but so the flange remains above the sink hole).
Now, apply silicone caulk to the top of the rubber gasket.

Now, grip the flange at the top of the tail piece and remove whatever's under the sink so that you can slide the rubber gasket onto the tail piece. Push the tailpiece down and the rubber gasket up until they're both tight against the sink. Now, put a pair of needle nose pliers into the tangs at the top of the tail piece and slip the large steel washer on from below and follow with the hex nut to hold the tail piece in place. Tighten the hex nut with a pair of slip joint pliers while preventing the tail piece from turning with the needle nose pliers.

Wipe up the blobs of silicone caulk, and then use paper towels to clean up the silicone film on the outside of the tail piece under the sink and on the top flange of the tail piece inside the sink. Paint thinner will dissolve silicone caulk even if it's partially cured, so finish up by wiping everything down with paper towels damp with paint thinner and allow time for the paint thinner to evaporate.

I'd leave the drain overnight at least before testing for leaks. Just put the plug in the drain, fill the sink and overflow channel and leave it that way for a while to see if anything leaks. Then pull the drian plug and drain the water into the pail you used earlier.

Throughout this post I refered to the thing you're installing as a "tail piece". That really should be called a "P. O. Plug".
Normally, bathrooms sinks use a combined drain and tail piece and the whole thing is called a P. O. Plug. Kitchen sinks use a separate strainer basket and tail piece.

 

...Throughout this post I refered to the thing you're installing as a "tail piece". That really should be called a "P. O. Plug".

AMAZING! Nestor, I've installed many of these over the years and didn't realize that they were not called "tail piece." Shees...I'm gonn'a have to use that some place. And for those of us that couldn't just let it lay with P.O. that stands for pop-up overflow.

Nestor...I'm kind of surprised you support the use of silicone when installing them. I've only used putty and when I encounter one that's installed with silicone, I HATE it.

The last sink I installed had silicone EVERYWHERE, on the rubber washer, every supply connection, under the seat for the drain, under the faucet. And yes it held for years. The problem is that when reinstalling...there ends up being pieces of silicone everywhere. As you know, the proper method when reinstalling is to have a completely clean surface for the silicone to seal. After spending a couple of hours using a razor blade to clean the silicone off the sink and out of the over flow cavity, I re-installed with plumbers putty. Most likely that's the way the next ones will go as well.

Just not a huge fan of silicone caulk....it has it's place and purposes, I personally don't think this is one of them.

Oh, and as a side note...the instruction manual also suggested the silicone way...so what you say is valid...but gawd I hate that stuff...

 

Rippy Skippy:

I'm not a big fan of silicone caulk either, but if you know how to remove the stuff, it's not a real problem either. I normally try to use plumber's putty instead.

However, from what I could tell from the poster's question, it was a Waltec P. O. Plug that he was installing, and I know from experience that the rubber grommet on those is very hard to "slide" on unless you use some sort of lubricant between the rubber grommet and the chrome. And, in my view, that Waltec design really does need something to seal between the threads of the P. O. plug and the rubber grommet. Silicone meets these two needs, and so I use silicone when installing Waltec P. O. Plugs.

I prefer Waltec P. O. Plugs.

AMAZING! Nestor, I've installed many of these over the years and didn't realize that they were not called "tail piece." Shees...I'm gonn'a have to use that some place. And for those of us that couldn't just let it lay with P.O. that stands for pop-up overflow.

Gimme a break. Take a look at the time I posted that. 5 minutes to midnight. It was late when it dawned on me that I had been using the wrong word throughout the post, so instead or going back and changing every occurance of "tailpiece" to "P. O. Plug", I just put a little note at the end. As long as I corrected the mistake, why gang up on me?

 

...why gang up on me?

Dude....I'm not ganging up on ya. Take a deep breath....

 

I just replaced my first strainer assembly/P.O Plug deal. The old one was only 4 years old and was rusting on the flange threads.

When I reassembled, I had "garden hose" leaks everywhere so I started over. I followed most of the steps listed above, including pipe dope on all exterior threads of the strainer assembly, and plumbers putty under the flange. Silicone caulked around all outside joints including a joint that you could turn round and round that leaked, no more leaks. Looks like crap but works great. Compared it to the rest of the strainers in the house - all were covered in silicone when the house was built in 04 so I don't feel too bad.

One thing I was unsure about was how tight to turn the drain nut? Manual said do not crack sink, which wasn't helpful.

 

I agree with dragon use the plumbers putty if you can.

 

I'm not sure how you would use plumber putty anywhere but under the flange. Could you explain, I'm interested to learn new tricks.

 

You mention that you have garden hose leaks...where exactly? If the parts are assembled correctly...there's no reason to silicone the heck out everything...it looks bad and when you need to perform maintenance it's just a PITA.

 

After retightening and application of pipe dope the leaks have disappeared.