Why Your Sink Could be Leaking

kitchen sink leaking
kitchen sink leaking

Plumbing and leaks–saying that it is like saying Electricity and shocks—the two just go together. Now, plumbing that is professionally performed should not result in any type of leak, however, it can typically be a given, when it comes to the novice DIY homeowner who imagines that plumbing components can easily be changed out or modified without risking the integrity of the entire system.

Generally speaking, anytime you go to work on one section of plumbing, if you are not excruciatingly exacting about preventing movement of any kind to the other pipes and joints that connect to where you’re working, you will most likely suffer a consequent leak. So, your sink could be kitchen sink leaking if you have ever done any type of DIY plumbing repair and such, underneath it.

Why You Should Always First Check The Sink’s Flange Fitting


When you are attempting to diagnose the cause of a sink leak, you need to begin your investigation at the highest point along the routes in which water travels both to and from your sink. The drain of your sink, being the highest point where water travels on its route away from the sink should be your starting point. When there is a leak in the drain, water will leak out from the rubber seal, and travel down the course of pipes, all the way down.

This means you could easily observe water dripping from a lower joint below, leading you to mistakenly believe that you have diagnosed the problem. Your kitchen sink’s drain contains something called a flange, which serves to create a watertight seal at the point where the drain pipe connects to the sink. Plumber’s putty that is applied around the lip of the sink’s drain works together with a rubber washer that is located directly behind the sink’s mounting unit, which is used to securely fasten the drain to the sink. Either one of these components can fail, causing a leak to occur whenever water drains from your sink.

This seal is frequently exposed to dramatic fluctuations in water temperature, causing it to expand and contract. Sometimes the cause of a leaky sink is a damaged or worn-out flange seal. To determine if the leak is coming from the flange, fill the sink with a couple of inches of water and then allow it to drain. Next, stick your head and a flashlight into the cabinet below and under the pipe to sink the connection point. If this is the source of the leak, you will see or feel some water there.

Broken or Missing Grout

One source of a kitchen sink leaking can be from faulty caulking or grout, which should go seamlessly around the entire circumference of the sink at the point where it joins up with the countertop. Depending on the type of sink you have and the way it is mounted, the way this caulking will be performed will differ, but anytime the line of caulking or grout is interrupted, what results is the creation of an area where water can travel from the sink and onto various areas below–usually under the cabinets.

Bad leaks that go undetected for extended periods of time can actually produce significant damage to the sub-flooring and even worse, so once you suspect the presence of a leak, quickly find the source and do something to remedy it.

The P-Trap

Oh so often the “root of all evil” when it comes to clogged drains, the P-Trap gets its name from the shape it forms. it is that little curved pipe that is connected to the piece of pipe that is connected to your sink’s drain, assuming that it’s a straight shot down and then angled into the wall. While at first thought, it would seem fairly straight forward to simply remove a P-trap, ream it out, evacuating all collected debris, and just snap it back on. This is partly true and partly false.

Again, the real problem here is performing this operation while being careful not to disturb anything else. And this is not easily accomplished. The P-trap can be replaced, but only as long as you are careful about what you’re doing. And then, there’s the issue of using plumbers’ tape, which is essential for creating a nice, watertight seal at the points where the pipes connect to the joints. In fact, anytime you undo plumbing pipes with the intention of putting things back together, know that you will need plumbers’ tape to exact the process. Without plumbers’ tape, you will experience kitchen sink leaking.

The Waste Arm

The source of your leak could be located within your waste arm, either produced by a crack in the pipe or a faulty seal at one of the joints at either end of the pipe. Your sink drain either stubs out from the back wall of the cabinet or extends through the floor of the cabinet.

The sink drainage line consists of an assembly of pipes and fittings. Typically it is at the joints or connection points that exist between the different sections of pipe that produce any waste arm leaks. All that may be needed is just re-sealing the joints properly, although you need to inspect the pipes and fittings for any telltale signs of corrosion, which can also occur, but not with as much frequency.

Tailpiece Leaks

On the bottom of the sink drain, you will find a tailpiece, attached to threads on the bottom of the sink drain at its top end. The tailpiece attaches at the other end to the P-trap (on the lower end) by slip nuts and washers. Plastic slip washers are implemented in conjunction with the slip nuts to effectively seal the tailpiece’s connections where they are threaded.

In order to diagnose a tailpiece leak, you will need to run water through the drain of the sink while observing the tailpiece using a flashlight. If your tailpiece is leaking, you would typically discover water to be seeping out of the connections, although occasionally the leak could be in the pipe itself. This problem is usually an easy fix—by tightening the slip nuts or replacing the plastic slip washers, you should find that the problem has been corrected.

Other Diagnostic Methods

By evacuating the cabinet under your sink of all its contents (just put them into a box for now) you will have more ability to diagnose the source of the leak. With your cabinet empty, you can actually take newspaper and lay it flat, to line the bottom of the cabinet under the sink and all the pipes in that space. Don’t wait too long to check the newspaper after using the sink, as the water could spread, with no accurate telltale “trouble spot” under your sink. And while you are down there, do a once over, to inspect the drain components for cracks and corrosion. This will help to prevent the occurrence of leaks in the future.

Whenever a DIYer is self-plumbing, it’s important that they understand the right amount of tension needed for joints, and that same advice applies to slip nuts, as over-tightening any plumbing component can produce some kind of malfunction. The general rule of thumb is to tighten parts to hand-tight, and then an additional quarter turn.


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