Author Topic: Seal pipe holes under kitchen sink cabinet?  (Read 3766 times)

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Offline mike1967

  • Posts: 52
Seal pipe holes under kitchen sink cabinet?
« on: September 13, 2017, 09:43 PM »
I just removed a broken dishwasher from my kitchen.  The dishwasher sits right next to the sink cabinet.

I have cleaned out the dishwasher area (dust and miscellaneous junk) and, with the dishwasher gone, noticed that I can see the supply pipes that run to the sink.  There are two holes in the wood floor, and the pipes enter the sink cabinet from the basement, through these holes.

A few years ago we had a sink mess, and water must have gone through these holes.  I know this because I found water in the basement (translation: shop) and the basement ceiling was wet.  Now with the two holes are exposed, I am wondering if I should seal them with water-resistant spray foam.  If the holes are sealed, then, if there is a sink problem in the future, the water will stay in the kitchen.  I think this is better than having it drip through the holes and into the basement.

I can also caulk the drywall / floor joint behind where the dishwasher sits.  I think the kitchen builder should have done this, for both water and air leakage reasons.

Thanks for any thoughts on this.


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Offline Holmz

  • Posts: 4010
Re: Seal pipe holes under kitchen sink cabinet?
« Reply #1 on: September 13, 2017, 10:05 PM »
Well a counter top with formica on MDF is a mongrel at the sink cutout...
Using some epoxy there is a good idea.

In you location I would still seal it with some spar varnish or epoxy at the endgrain of the inside of hole.

Whether or not you want to foam it, seal, or caulk it... I am not sure.
If the cabinet slowly soaks up moisture it may be worse... (dunno)

A moisture alarm would be where I would be looking, to have some alert when the water is shouting out.
Then shut the water off, vacuum it up, and get a fan going.
The other approach is to build the kitchen like a boat and use spar vanish or epoxy everywhere.

Offline mike1967

  • Posts: 52
Re: Seal pipe holes under kitchen sink cabinet?
« Reply #2 on: September 13, 2017, 10:09 PM »
There is a 4" gap between the finished floor and the bottom of the sink cabinet.  So, if there is water that goes through the holes in the bottom of the sink cabinet, it will sit on the floor (if I seal the floor holes).  This is not as bad as ruining the sink cabinet, I think.

If I ever rebuild this kitchen, I will take the boat approach.


Offline Holmz

  • Posts: 4010
Re: Seal pipe holes under kitchen sink cabinet?
« Reply #3 on: September 13, 2017, 10:50 PM »
We are in the same boat, as they say.

I would epoxy the wall of the hole with a throw away brush, and then your foam sealer sounds like a winner for ease and purpose.

I just did coat #4 on the kitchen counter edge with spar varnish.
It is like the Flipper show at Seaworld or Marineland, when cooking with water and god knows what getting onto the counter.

Offline Bob D.

  • Posts: 835
Re: Seal pipe holes under kitchen sink cabinet?
« Reply #4 on: September 14, 2017, 06:56 AM »
You can also get a under sink mat made by WeatherTech, yeah, the car floor mat guys.

It's something new they have added to their product line. Haven't seen or used one myself
but it might be an option for you. Sounds like your supplies and drain drop out the bottom
of the cabinet so you would have to cut to fit around the pipes. Depending on how the sink
was roughed in this may or may not be an easy task or one that finishes with a neat look.

Remember that your hot water pipe will move as it heats up when water is running (and
again as it cools off back to room temperature), assuming it's copper that is, maybe not a
problem with any of the plastics but since I have never owned a home with anything other
than copper plumbing I wouldn't know about that. So if you seal up tightly around the copper
then as it moves it might make some noise.

You could wrap the pipe with a thin sheet of plastic that your sealer or caulk will not adhere to,
then caulk around the pipe and remove the plastic after it cures. Then you are left with the hole
closed up and only the slightest gap between the pipe and the cabinet floor.
It's a table saw, do you know where your fingers are?

Offline rst

  • Posts: 2036
Re: Seal pipe holes under kitchen sink cabinet?
« Reply #5 on: September 14, 2017, 07:11 AM »
I've sealed water supply pipes with fire stop spray foam and never had an issue. I foam is flexible enough to take up any movement.