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Question DetailsAsked on 3/9/2017

I have a double sink and every time i turn on the faucet water comes pouring out from under the sink cabinet

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3 Answers


I presume from what you said this only occurs when you use the sink - not a continual leak, so leaking water supply pipe/tubing or leaking shutoff valves is NOT the problem in that case - nor is total main stem/faucet handle seals failure or corroded/cracked faucet fixture in the constantly pressure-retaining portion of it (the part "upstream" of the shutoff washer or seat or ball in the faucet).

I am also assuming at points in the discussion below that you have a cabinet under the sink which has an elevated "floor" in it, separate from the kitchen floor. If not adjust procedure as appropriate.

Get out a flashlight (and if possible use a second person to turn the water on and off in sink on command so you are limiting the amount of water being dumped out) and look around in the cabinet under the sink - first look for water or staining without turning the water on to try to tie down the source, and look for any loose pipes or hoses or staining or lime buildup on hoses or pipes which might indicate the leak point without having to run the water. Run all over all pipes and hoses with paper towels to dry then - start and top and work down on each one, checking frequently (or use bare hand) to see where the top point is that wetness shows up - that is usually the leakage point. Of course, points on the same piping/tubing below that point will be wet from the water running downhill (and possibly dripping onto the cabinet floor some distance from the actual leak point). Also, dry the cabinet floor, then lay out paper towels over it to catch (and show) where any leaks are dripping when you run the water.

If leakage only occurs when dishwasher is in use (or recently has been) then you need to be looking for a leak from the dishwasher (if coming out on the floor under the base of the cabinet, not if coming out in the elevated cabinet floor under the sink), or leakage from the dishwasher discharge hose or air vent at/under the sink. IF it occurs when dishwasher has NOT been in use, then not a dishwasher or dishwasher discharge hose related item, unless the dishwasher hose has broken or come disconnected from the garbage disposal or drain line "barb" connection, in which case it might leak due to backup when water is run in the sink - and would flood probably dramatically if dishwasher were run.

[To help identify lines - dishwasher water supply line is almost always flex tubing - plastic or copper and leading through the side or back of the cabinet to the dishwasher, the dishwasher drain line is almost always flex plastic hose coming into the cabinet from the dishwasher to the garbage disposal or to a connection "barb" on the drain pipe, usually leading first through an air vent with slotted holes in the side of it [google "dishwasher air vent" for images if desired] - can be reinforced polyethylene (clear or colored), or commonly a corrugated (vacuum cleaner hose appearance) about 1 inch hose of almost any color. So those should be pretty easy to identify. This as opposed to water supply lines to the faucet which are commonly copper coming into the cabinet then flex copper tubing to the faucet but can be many materials but will lead to the faucet (separate hot and cold lines) - normally with shutoff valves on both hot and cold where the flex tubing to the faucet comes off the main water lines. Sink drain lines are commonly 1-1/2 to 2 inch black or white plastic but can be steel, iron, brass, etc in older homes, but connect to the bottom of the sinks or garbage disposal and lead through a U-shaped trap to a 1-1/2 to 2 inch pipe into the back wall or floor, so they are pretty obvious].

If in your visual inspection you find such a wet or stained/limed up spot, put a container under it to catch the water during the water test, to prevent further water damage.

Then run the water - use low flow rates initially unless you find it does not leak noticeably except at full flow, and look for water possibly coming out at the top of the sink from the faucet/sprayer/air vent and running down off the sink flange and under it and down into the cabinet, and also look inside the cabinet up under the sink - up under faucet or sprayer for possible faucet leak directly from the bottom of the faucet fixture or sprayer, from drain pipes or their connection to the sink or garbage disposal, or from the garbage disposal. Very rarely, leak is from the sink itself other than at the drain line connection, due to a cracked sink.

Also, if an undermount rimless sink (entire sink is mounted up under the countertop, with no rim on top) look to see if if that seam is open - water would only escape as a leak if sink were full or water was running so it ran down over the rim of the countertop, not directly into the sink, in this case.

Also - pay attention to whether this happens when water is run in either side of the sink, or only if run in one side - if only when running in one side of the sink - then NOT a water supply line or faucet/sprayer problem, your problem is in the drain line from that side of the sink or its connection to the sink or garbage disposal.

If leaking at the garbage disposal, then you have a connection leak if leaking at a connection, a sink mounting ring/seal issue if coming off the top of it, likely a motor seal leak or cracked housing if coming out the bottom center of the disposal, or a worn-through wear ring in the disposal if leaking through holes or tears in the side of the disposal, which in the latter two cases means disposal replacement time (not economic to fix more than a connection leak in a disposal).

If there is no evidence of wetness or leakage in the cabinet itself or on the cabinet floor but water still starts coming out under the base of the cabinet when you run the water, then you have a corroded or cracked drain line behind the cabinet or in the wall.

If you cannot find the source or are not able to do this sort of DIY investigation yourself, or find the leak but are not up to repairing it yourself (sometimes it is just a loose threaded lock ring on plastic drain pipe you can hand-tighten), then obviously Plumbing is the Search the List category to find a well-rated and reviewed vendor.

Answered 3 years ago by LCD


BTW - here are a couple of links to similar questions with more detail on some of the possible causes - probably mostly repeat of what I said before, but might help:

Answered 3 years ago by LCD



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Answered 3 years ago by Member Services

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