Water bubble out from concrete slab surface when the downhill 12-foot far away kitchen sink is dra

[John Chen]

Recently we spot damaged dry wall at the corner of the family room (under the external wall). Later on we realized that water bubble out from the damaged area when a nearly 75% full island kitchen sink is drained. A few seconds after unplugging the drain plug, I can hear water rushing and goggling sound and then water burst out above the slab. No sign of water if we let faucet free running. I understand that the kitchen sink drain may be partially blocked, however, I am puzzled why water burst so strong (as under-slab leaked water will have to travel a fairly long distance and seep thru the concrete slab. Note: The damaged area is about 12-feet uphill from the sink.) The plumber claimed under-slab drain pipe leak directly under the sink. Doesn't drain pipe always go downhill (to drain to the street)? Really confused.

 

[Jadnashua]

Water will only go downhill on its own...but it sounds like you have a broken pipe under your slab since you should NEVER get waste water coming up through it when draining anything. The difference between just running the faucet verses draining the sink is the sink drain can accept lots more water than the faucet can put out and it's reaching the break or hole in the piping.

 

[Sponsor]

 

[John Chen]

Thanks for the quick response.
"Water will only go downhill on its own.." Indeed and that is where I am deeply puzzled. It is fairly likely that I have a broken pipe underneath the slab somewhere. If it is drain pipe then water should leak downhill somewhere. Could it be the vent pipe, especially when the drain pipe is partially blocked (thus, waste water raises up in the vent pipe when the sink is drained.) The way that water bubble out also confused me a lot. I would naively expect water only slowly sip through the concrete slab.

 

[FullySprinklered]

This is one situation where having someone in to scope your pipes would be beneficial. They can precisely locate breaks, bellies, and blockages and allow repairs to be done with a minimum of excavation. Or, you can stand there looking at the slab and speculate it to death.

 

[John Chen]

This is one situation where having someone in to scope your pipes would be beneficial. They can precisely locate breaks, bellies, and blockages and allow repairs to be done with a minimum of excavation. Or, you can stand there looking at the slab and speculate it to death.

Couldn't agree more. In fact, I had one Leak Detection specialist came over to locate the leak. The plumber said the leak appears to be under the kitchen sink (under-slab). Still not sure how water travels more than 11 feet uphill and come through concrete slab fairly rapid. No obvious sign of concrete openings or cracks (some areas are not visible for direct observation as drywall not fully removed.) Without some understanding in the root causes, it leaves me wonder to repair what and where.
Thanks for the reply and suggestions.