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About Sharon McCarthy
Expertise
I can help with most questions about residential plumbing problems including septic systems, and some questions about irrigation. I have no experience with commercial installations or codes.

Experience
I have been a sole-proprietor service plumber in two small towns north of Phoenix Arizona for 26 years.

Publications
I had a monthly column in the United Steelworkers of America, local 1033, newsletter 1978 to 1982. I wrote an article for "The Theosophist" in 1977. I've written dozens of letters to the editor in many newspapers.

Education/Credentials
High school and three years of college. My step-father, having worked 40 years in the plumbing trade in Chicago, taught me for two years. The rest has been hands-on experience.

Past/Present Clients
Many hundreds of good people in Cave Creek and Carefree Arizona

You are here: Experts > Home/Garden > Home Improvement/Repair > Plumbing in the Home > Warm water from the cold faucet

Plumbing in the Home - Warm water from the cold faucet

Expert: Sharon McCarthy - 11/9/2009

Question
QUESTION: My house is on a slab. Built in 1973. I've just noticed over the past couple of days, a couple of the tiles next to the kitchen sink were warm. It's not been warm outside. Also noticed that the cold water (not a single faucet sink) would run cool then run pretty warm before getting cold. I stuck my head under the sink and could hear water "on" similar to what i'd hear if my outside hose were on very low. I turn the water off at the water heater and the sound goes away. I'm guessing a leak below the cabinet or in the wall maybe but sick at the thought that it could be a slab leak. No idea where to begin to confirm or where to look next. Also curious if it's a slab leak - how big of a job that is. Thanks!

ANSWER: Dear Scott,

  That does sound ominous. I presume you checked inside the cabinet for any sign of water leaking. If it is a leak under the slab, it would be a pretty messy job. Do you have a dishwasher? Did you look underneath the dishwasher [just in case]?

  If you don't know a dependable plumber, ask at a local Ace Hardware. They usually have a list of local tradespeople that have been recommended to them or spend a lot of time there. You need to have a trustworthy service plumber take a look at this.

  If there is a leak under the slab, you'll have to have a hole jackhammered through the floor to get to the pipe. The fact that you can feel heat under those tiles might help. Often when there is a leak under a slab, even if you hear water running close-by, the leak could be 5 or 10 feet away. Usually in the case of a leak under the floor, a locating service [in the phone book under Leak Detection Services] needs to come out and pinpoint the exact spot.

  These people use a machine that looks like a metal detector, but it's sensitive to the sound of running water. The locating services usually guarantee the leak will be within inches of where they make their mark. They generally charge around $200-250 to do this job. They also often have plumbers who will make the repair, or you can have your own plumber do it.

  Do some checking first, make sure the people you call are recommended. There are a lot of thieves in the business, sad to say. Good luck with this. Sharon

---------- FOLLOW-UP ----------

QUESTION: Sharon - this has been a while but it is a hot water leak under the slab. it's just at the edge of the cabinet below the sink. identified by a leak detection service. 2 plumbers suggested tunneling from the outside wall to save tile on the inside. looks like it would be a little more than 3'. since 90% of the estimates are labor, i was going to dig myself. do you know how big the hole needs to be and how deep i would need to go before turning toward the house?

Answer
Dear Scott,

  Your first question came up first, before your follow up question. I read the first sentence and thought Am I losing it? I had this exact question before!!!

  Wow, tunneling under. I suppose this would cause less damage. I'm not sure what you mean by saying how far would you need to go before "turning toward the house". Do you mean DOWN? I expect the kitchen sink is right at an outside wall. I'm trying to recall how a house is constructed from ground up when it's built on a slab. I worked with my step-father a few years on new construction plumbing but that was 26 years ago!

  I believe, before the slab is poured, a trench is dug around the perimeter of the future house and 3 or 4 rows of concrete block are laid in the trench. Lengths of rebar are pounded into the ground inside the spaces in the block, and concrete is then poured into the spaces. This block border is called the "footer". It holds the concrete in that is poured for the slab, plus the footer is the base of the ouside walls.

  I can't tell you how deep that footer is, but I'd guess it's a pretty solid mass lower than the level of the slab floor. So you'd either have to dig down under the footer, or break through it, though I'm not sure that would be possible. So assume you have to go under the footer. The depth may vary depending on the location, climate, codes, etc.

  Once under the footer you said you'd need to go about 3 feet in, to reach the leaky pipe. The hole would have to be big enough for a person to crawl in, go three feet with tools in tow, and have enough room to light a propane torch, then cut, refit and solder the pipe.

  Regarding damaging the tile, most of the time, when inside tile is laid, the tile guys will over-order so there will be some spares left for repairs and cracked tiles. My son bought a 30 year old house in Phoenix last year. He was cleaning out the crawl space under the roof to store some boxes, and found several boxes of tile that matched his kitchen and bathrooms. Is it possible you might have some spare matching tiles somewhere?

  It really would be easier to pull up 6 or 8 tiles, rent a jackhammer and bust a hole in the slab right over the leak. I know plumbers who did such a job in one morning, made the hole, repaired the pipe, collected their checks and were out the door. Fixing it would require backfilling the dirt, pouring some cement and replacing those 6 or 8 tiles, which you could do. That hole would only need to be about 18" square.

  Just a thought. Tunneling under sounds like a nasty job. Also, how big is the plumber?? Just joking, but really, if he's a big guy he'd need a big tunnel! Good luck! Sharon

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