Unknown 1 1/2" Copper Pipe Under Dishwasher - Must be Removed

[reb101]

Pulled out the old dishwasher to install a new one. This 1 1/2" copper pipe (see photo) is sticking up from the concrete slab floor, blocking the installation of the new dishwasher. It appears to be capped with a soldered brass end cap. There is a keystone image stamped or cast into the cap.

I estimate the kitchen addition was added in the 1970's. There are two drains that pass into the basement adjacent to the kitchen slab. Both are Copper. I suspect this is an unused drain or drain vent but not sure. I'm afraid it could be gas or water.

The option just occurred to me that I could place my ear on the cap, and have a helper tap with a hammer on the drains, water lines, and gas lines in the basement. Another complication is that this addition was built on an adjacent lot in a small town. There is a 3/4" cold water supply line under the sink that is not connected to my main supply line. It used to supply water to a fish pond, but I capped it off (above a valve) years ago. It could be connected to that water supply.

I need to cut this pipe off flush with the floor. If it's only an unused drain, any suggestions to seal it. If it's gas or water I assume I"m going to have to bust out the concrete around it to get rid of it.

On a related issue... any tips on getting the teenagers to hand-wash the dishes ?

 

[Gary Swart]

It's not gas, much too large. It's not water, for the same reason. I might have been for a drain or vent, but serves zero purpose being sealed. Can you find where it is under the floor? If so, cut it off under the floor. I'd cap it just to be sure nothing drained back into it. If you have to break out some concrete, don't despair. It isn't that hard. You can rent a rotary hammer/drill that will do the job. Raises some dust for sure, but you only need to get enough chipped to get below the floor far enough to cap the pipe.

 

[Sponsor]

 

[hj]

It could have been the drain for an old gravity drained dishwasher. If so there will be a trap under the floor. Remove the cap and check what's under the floor.

 

[reb101]

Thanks for the feedback. I placed my ear on the capped pipe while my daughter tapped on the drains, water, and gas pipes in the basement. Just as you both suggested, the pipe was verified to be a drain. I'm going to cut it off tonight with a 4 1/2" angle grinder with a cut-of blade, then change blades and grind it smooth with the surrounding concrete floor. The best solution for sealing it that I can come up with is to insert a 1 1/2" rubber drain plug into the cutoff pipe and seal it in place with silicon calking.

That's interesting that the drain was probably there as an old gravity drain for a dishwasher. That makes me feel a lot better about removing it.

 

[reb101]

Job is done. The copper pipe was quickly and easily cut off flush with the concrete using an angle grinder. I coated the inside of the pipe and a rubber drain plug with silicon calking then pressed the plug into the pipe about 1" deep. Filled the pipe above the plug with 3/4" of silicon calking.

(I first tried to use an Oatey expandable plug with wingnut, but it stuck up too high from the floor and caught the rear bottom edge of the (Bosch) dishwasher as I tried to slide it back. Tried to raise the back end of the dishwasher with the leveling adjustment to get it over the expandable plug, but it was just too tight under the counter. )

 

[Plumber69]

Job is done. The copper pipe was quickly and easily cut off flush with the concrete using an angle grinder. I coated the inside of the pipe and a rubber drain plug with silicon calking then pressed the plug into the pipe about 1" deep. Filled the pipe above the plug with 3/4" of silicon calking.

(I first tried to use an Oatey expandable plug with wingnut, but it stuck up too high from the floor and caught the rear bottom edge of the (Bosch) dishwasher as I tried to slide it back. Tried to raise the back end of the dishwasher with the leveling adjustment to get it over the expandable plug, but it was just too tight under the counter. )

You don't have to use the wing nut. I used a small nut once and grinded off excess tread once