Hello:

I am stumped so far at finding a persistent leak for a client underneath the kitchen sink... the plywood is saturated in spots! It's a double basin with a single stem kitchen faucet and one air gap. I have recently chaulked the sink very well thinking the water was getting through that (gaping holes!) but the leak is even more pronounced. I also lifted the faucet enough to apply sealant (wasn't there before), and tightened the air gap nut. But the leak persists.

Any ideas?

I have an appointment with my customer Jan 6, 2017, and I next plan to:

1. Undo the faucet nut, pull up the faucet and see if the one or both of the copper supply lines are leaking between the level of the counter and plywood (going within the plywood, unseen). There is no leak coming down from the faucet so I'm not too hopeful, but I want to rule this out.

2. Replace the airgap; there is a lot of water coming directly underneath and I'm not sure if the air gap is bad or water is leaking from the gasket.

Any other ideas would be helpful.

Thanks.

Of your two possibilities, I would go with #1 option. I have encountered this before although the water usually will remain under the escutcheon plate and travel down the faucet supplies where it can be seen.

Gosh, yes. I am hoping that I will see a leak at one of the copper supply lines when I raise and temporarily turn on the water. The bulk of the leak, however, seems to be directly underneath the air gap and working back towards the backsplash. It's extremely heavy saturation of the plywood in these areas.

I have such a great video (and pics) on this if only I can learn how to post on photobucket.

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Hope this video uploads ok!

Don't think the video loaded...trying to link three pics..

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the leak at the faucet appears to be coming from around the base. yeah, do loosen it, clean it and silicone caulk it well before tightening.
as for the air gap, take it apart and clear the discharge side hose.

My bad. I forgot to mention that the first thing I did was to clear the disposal drain and removed a huuuuuuge turd that what blocking it! After that I had just tightened the air gap nut but the water keeps leaking---it seems its coming from right under the air gap the most (and possibly at the faucet as well.) What I haven't tried is removing and sealing the base to it. (I'm just going to replace with a new air gap.)

sounds like you are on the right track..

OK. So I went back and did what I wanted to do. But...to my surprise...the chalk I had laid down was all mushy and not dried yet! And that was after about several days! And everything was still leaking.

1. I undid the nut to the single stem faucet and lifted stem over the sink and turned on the water while keeping it lifted. Unfortunately, the stem is incased and there is no way for the water supply lines to leak except down (and it wasn't.)

2. Before I got there, the customers had washed dishes and I can clearly saw a lot of fresh water saturation underneath the old air gap, and the at the back splashboard. I mean, a lot!

3. I installed a new air gap and even chalked. The old one had no gasket on top (incorrectly installed) and the bottom was chewed up.

4. I removed all my old chalking, and applied afresh.

5. Five days later, the customer texted and said the chalking was still wet and sink is still leaking. . ????

6. He also reported that another guy came by (for some other work), removed the chalking, dried it (heat gun?), and applied chalking that was dry to the touch in a couple of hours. ???? Ugh??

7. I re-read my chalking and it said it would dry to the touch but could take 7-10 days to cure. By the way, customer had a heat and fan pointed at the sink and it still didn't dry.

8. Customer reported no more leaks after new chalking. I asked him which chalking the other guy had used but he didn't know, just that it was, "100% silicone clear 30 mins"

Well, I am dumbfounded why the my silicone never dried to the touch overnight (to cure days later.) I used clear silicone that was for bath and windows. I did notice when I removed my chalking (the second time), there was a lot of water behind sink/plywood join. So maybe it was too wet to apply? I had dried it by sticking paper towels in between and drying the areas where the sink and plywood joined and the two surfaces seemed dry at the time to me.

I'm glad my customer resolved it...I have not had any more updates. But this is still all puzzling to me.

Any thoughts?