Unidentifiable copper pipes protruding from slab...

[trophft]

First time post, so go easy on me.

The situation:
Waste water backs up into our kitchen sink (a couple inches) during washing machine drain cycle, but quickly recedes once the drain cycle ends. Had plumber snake the line twice (once down the standpipe and once from the city cleanout in yard) but the problem persists, so I don't think there is a blockage. I assume it's just too much water, too fast, for this 40 yr old slab house; or the standpipe isn't vented properly...

But here's the mystery: When this situation happens after heavy rains, water also comes up from two mystery pipes. One is located in our broom closet by the laundry room, the other is located in the wall behind our guest vanity on the other end of the house. (See photos)

I jammed some plumbers putty into one of the pipes to cap it off after this happened the first time, to see what would happen. That's when I discovered the 2nd pipe behind the guest vanity (because the water had seeped under the wall and into the bedroom)

So, what are these pipes? Where do they come from and where do they go? and why does water come up from them and flood my broom closet and bedroom!?!

The mystery continues...

 

[Caduceus]

Just a guess at this, but if the PEX piping is an indication of work that was done after the house was built, you may have had a ruptured copper pipe under the slab. The pex could be a rerouting of the water pipe that broke underground, but the ends of the broken pipe were never capped off.
Now when you have heavy rains, the soil gets saturated and soaks into the broken pipe underground and fills it up.
You may be able to put a brass threaded cap on the pipe in the first photo and a Shark Bite cap on the other one.

 

[johnjh2o]

Caduceus, nailed it. But what I will add is you will be looking at a total re-pipe in the near future. If one line failed under the slab the others won't be far behind.

 

[trophft]

Caduceus and John, MUCH appreciated. The PEX is from a repair done before we purchased home and is the only PEX line (running through attic to guest bathroom).
The first backup incident was just water coming up the kitchen sink. The second incident was kitchen sink AND water coming up pipe #1 in the laundry closet. And after i plugged it with a wad of plumber’s putty is when we discovered water in kitchen sink AND the other open pipe in the guest bathroom. My concern is if i cap both those open pipes, then where will that water go next time? (besides the kitchen sink of course!) Could finally overflow the standpipe behind washer maybe. I guess if Caduceus is correct then those two pipes are the two ends of the same hotwater run and there isn't a third mystery pipe waiting to overflow behind my walls.

However, my wife is confused because if those copper pipes in the slab are supply lines to various fixtures throughout the house, then why do they overflow when our washing machine is "draining" down a different set of drain pipes altogether; regardless of rains or soil saturation. (does that make sense?)

Thanks again for your help.

 

[IFIXH20]

Sounds like the kitchen/laundry drain is clogged or have a partial bolckage and the water is overflowing out the laundry stand pipe then running in the wall and over the floors. If one of the open lines is under the laundry box then water could be leaking into the line and filling it. Have you physically seen water come out the lines or you just notice the wet floor. Your wife is correct the laundry/kitchen drain has nothing to do with the water lines.

 

[trophft]

IFIXH2O, We just tested it and ran the washer's drain cycle. Water immediately came up both copper pipes (i removed the putty plug on pipe #1 for the experiment). so it is definitely drainage related. We've never had the standpipe overflow, just he kitchen sink back up and then the two mystery pipes.

 

[IFIXH20]

Caduceus and John is totally correct the old water lines is allowing water into the pipe. With that said sounds like you drain line has failed as well (broken or has a hole in it under the slab)

 

[trophft]

IFIXH20,
So the possible failure in drain line is potentially causing super saturation under the slab right near where this copper line is busted and the water is just going up into this pipe (thus coming up out of both ends)...? Is that random coincidence that the drain pipe failure is in such close proximity to this old busted copper water line? (caveat: I know absolutely nothing of plumbing layouts or where/how water lines and drains are run in or under old slab homes.) I just think its crazy that a drainage issue w/ the washing machine could have any effect on an old copper water line in the slab, but thats why I'm on here asking for pro's help!
Thanks again for all your help!

 

[trophft]

Someone mentioned that the busted water line and the drain line might share the same trench. Perhaps that would explain it. I thought the copper lines were in the slab, and the drain pipes were under the slab, but like i said I know NOTHING about plumbing layouts or basics.

 

[Caduceus]

Yes they could share the same trench or just be in such close proximity to each other that what affected the water line in the past has also affected the drain. Water line breaks under slabs can cause washout of the supporting soil and gravel. A plumber or leak detection company may be able to pin-point the break or camera the drain to recommend appropriate action.

 

[johnjh2o]

From what I can see of the waste lines it appears to be no-hub cast iron. Which is a light weight cast iron pipe that is prone to failure.

 

[trophft]

Big thank you to ALL for the suggestions and ideas! Plumber came out yesterday and snaked standpipe, hit some obstruction and couldnt get past it. Then snaked the kitchen sink and hit mud, mud and more mud. So they're scheduled to tunneling tomorrow and reroute the W/D and kitchen drain lines to a new tap on the city sewer (since our main drain line is on the opposite side of the house and i didnt want them to tunnel all the way to link up w/ the main drain). The W/D is on an outside wall and the kitchen sink is on the other wall of the galley, so they just need to tunnel a few feet under for the W/D, and about 6 feet under to reach the kitchen sink, then its a 60' run down the side of the house to hit the new city tap.