I have a wet spot on the outside of my foundation. It is a block proprietor and a slab poured inside. Pipes run under slab.

When I first noticed this I checked the water meter for 24 hrs several times to see if I was losing pressure, but there was no movement on the meter after 24 hrs. I checked it several times.

Then I was away for a week (with water turned off) and when I returned it was still oozing this white paste. Wet , white looks like tooth paste. Don't see any wet spots under carpets or other floors. About 3" round about 8 inch from top of foundation.

Could it be a spring ? It's not waste water because I put blue dye in the toilets and it remains white. White paste consistently.

Had a plumber out. He did the same meter check for two hours but it did not move. Really has me stumped. The paste can be wiped off, which I did just before this picture and the "paste" never hardens, stays pasty. The circle is not a perfect circle it is just looks like that in the picture.

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  • Could this be above where the water service enters the house by any chance? – ThreePhaseEel Feb 15 '17 at 22:55
  • No, no plumbing within 20 ft. Like I said I checked the water meter and it never moves when shut off then back on after hours. Thanks tho.... – George E. Feb 16 '17 at 0:05

My guess is that a lump of unmixed something-or-other made it into the concrete pour. If it was portland cement it would have cured long ago, so maybe it's lime, which is added to concrete as a flex and waterproofing agent.

Lime concrete, produced by this mix, makes a good base for load bearing walls, columns, or laying under floors because it has a degree of flexibility that regular concrete does not. It also has a certain waterproof property to it that prevents subsoil dampness in floors and walls. Additionally, lime concrete can be made easily and cheaply while still providing a durable material that resists weathering and wear and tear.


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  • Thank you for your answer. It is a 15 yr old house, I'm in it 6 yrs.. if the white "stuff" that come out hardened than I would say cement or even efflorescence but it never hardens. I wipe if off and in a day it's seeping out again.. Thinking maybe a drain is broken under the slab. No it always drains out to the street. You cant put your finger into it that wet circle,. Its hard like 1/2 inch beneath the o/s wet part. I'm lost ! – George E. Feb 15 '17 at 19:19

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