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Thread: Very strange moist spots on concrete

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    Very strange moist spots on concrete

    I just noticed for the past 2 weeks or so there are 2 very small moist spots on the concrete deck around the pool, the spots are about 1/2 inch in diameter, do not seem to get bigger, they are just slightly moist but not wet, there are no cracks on the concrete, I don't know if there is a leak in the pipes, I do not seem to be loosing water or chemicals, I do have an automatic leveller, if there was a leak, fresh water will be added automatically and my salt level will come down, but that is not the case. The deck was poured about 10 months ago. I also have sprinkler pipes in the same vincinity. I am trying to find out if there is a leak in the sprinkler system. I can't think of any other reasons. Anyone has any ideas?
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    San Juan 8500 gal Fiberglass Pool, Sta-Rite Max-E 1 HP pump, Star-Rite System 3 Cartridge Filter 300 sq. ft,
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    stever's Avatar
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    Re: Very strange moist spots on concrete

    No great ideas here -- A portion of the deck that is a little thinner can cause mousture to get through in a small area -- but where is it coming from? Is there groudwater in the area? Septic leach fields? Very accurate OCD birds?
    Pool: 625 SF Free-Form In-Ground Shotcrete Pool w/7.5' dia spa.(8 jets), 24" raised bond beam (22,500 gal)
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    Re: Very strange moist spots on concrete

    The concrete deck is is uniformly quite thick, about 8 inches, with rebar and wiremesh, my thinking is, even if there is a leak in the pipes under the concrete, it will take a lot of pressure to force the water through the concrete, flowing water from the return pipes should not generate so high pressure, wouldn't the water take the easy way out by going down the earth, the grass nearby is actually quite dry. The mystery continues.
    OH TWINS
    San Juan 8500 gal Fiberglass Pool, Sta-Rite Max-E 1 HP pump, Star-Rite System 3 Cartridge Filter 300 sq. ft,
    Sta-Rite Max-E 200,000 BTU gas heater, Aqua Logic SWG with P-4 panel. Goldline wireless remote control,
    3 Jandy Neverlube Valves with Goldline motorized control, iRobot Verro 500 pool cleaner
    5 Poolstar 1000 LED Lights, LED strip light at waterfall, Prozone Ozonator PZ7 with degasser column,
    Jandy Auto Waterfill, Aquamatic motorized pool cover, Poolbuster Max CC handheld vacuum.

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    Re: Very strange moist spots on concrete

    If it's that small and won't evaporate or spread, I bet it's not water but rather some kind of oil spot. Not neccessarily motor oil....a stepped-on peanut will leave an oily spot on concrete....as will many other foods.
    Dave S. - Forum owner
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    Mod Squad JohnT's Avatar
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    Re: Very strange moist spots on concrete

    Quote Originally Posted by duraleigh
    If it's that small and won't evaporate or spread, I bet it's not water but rather some kind of oil spot. Not neccessarily motor oil....a stepped-on peanut will leave an oily spot on concrete....as will many other foods.
    My thought exactly. Put a drop of water on the deck and watch how it spreads and soaks in. Sun tan oil is a possibility too. Even bird droppings can leave an oily spot for a while.
    TFP Moderator
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    monkeywrench's Avatar
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    Re: Very strange moist spots on concrete

    I'm trying to recall, exactly which chemical I added to the pool I believe it was to increase hardness(not sure) and I don't know the chemical name either but as I was broadcasting the bebe sized pellets some got on to the concrete and made these wierd water spots like you describe. The faded away rather quickly,(couple of hours).
    Have you been broadcasting anything lately.

    jb
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    Re: Very strange moist spots on concrete

    Thanks for all the help, the spots are actually getting slightly smaller. when I rub my finger on, they do not feel oily, the spots are just damp but not wet. I have not been broadcasting anything lately. It almost looks like a burst pipe burried in the concrete to create that kind of water pressure to permeate the concrete. There are flex pipes under the concrete nearby but not embedded in the concrete. As I said, the earth next to the deck is not even too wet. The pool continues to function properly. So will keep an eye on. It's going to rain for the next four days, thanks to hurricane Ike, I will report back next week.
    OH TWINS
    San Juan 8500 gal Fiberglass Pool, Sta-Rite Max-E 1 HP pump, Star-Rite System 3 Cartridge Filter 300 sq. ft,
    Sta-Rite Max-E 200,000 BTU gas heater, Aqua Logic SWG with P-4 panel. Goldline wireless remote control,
    3 Jandy Neverlube Valves with Goldline motorized control, iRobot Verro 500 pool cleaner
    5 Poolstar 1000 LED Lights, LED strip light at waterfall, Prozone Ozonator PZ7 with degasser column,
    Jandy Auto Waterfill, Aquamatic motorized pool cover, Poolbuster Max CC handheld vacuum.

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    Re: Very strange moist spots on concrete

    The spots are still there. Anyway, the rain wasn't as bad as forcasted, so I was able to do more investigation. I shut off the water supply to the backyard, so both the sprinkler system and auto-fill are off, I even opened the sprinkler valves to release the water pressure, and I closed the pool cover to minimize evaporation. After 36 hours, the pool water level had not dropped. The damp spots are still there. So I really don't know where the water comes from? Meanwhile I am trying to enjoy the pool for about another 4-5 weeks and it will be closed for the season.
    OH TWINS
    San Juan 8500 gal Fiberglass Pool, Sta-Rite Max-E 1 HP pump, Star-Rite System 3 Cartridge Filter 300 sq. ft,
    Sta-Rite Max-E 200,000 BTU gas heater, Aqua Logic SWG with P-4 panel. Goldline wireless remote control,
    3 Jandy Neverlube Valves with Goldline motorized control, iRobot Verro 500 pool cleaner
    5 Poolstar 1000 LED Lights, LED strip light at waterfall, Prozone Ozonator PZ7 with degasser column,
    Jandy Auto Waterfill, Aquamatic motorized pool cover, Poolbuster Max CC handheld vacuum.

  9. Back To Top    #9

    Re: Very strange moist spots on concrete

    Take a hair dryer and hold it on that spot and see if it dries up. If you cant do that use a leaf blower. If its water it should dry up very quickly. Look to see if it returns in the same spot.

    If it were a underground leak it would get bigger not stay the same. Make sure also that you dont have anything overhead that is dripping.
    25,000 gallon freeform inground gunite pool with 12" raised spa. 3.5'- 6.4' deep.
    2 skimmers, 6 returns and bubbler on sunshelf.
    Jandy 1.5 hp pump, Jandy valves, Jandy CL340 cart filter, Jandy Aquapure 1400 SWG, Polaris 280 w booster, Jandy LXI 4000 heater.
    White plaster, flagstone coping, custom tan tiles with decos on raised spa.
    Pentair lights.
    650 sq ft concrete deck.

  10. Back To Top    #10

    Re: Very strange moist spots on concrete

    OMT. Did you put muratic acid in the pool and possibly drip some on the deck? That will etch the concrete and the result with be a dark spot that may look wet.
    25,000 gallon freeform inground gunite pool with 12" raised spa. 3.5'- 6.4' deep.
    2 skimmers, 6 returns and bubbler on sunshelf.
    Jandy 1.5 hp pump, Jandy valves, Jandy CL340 cart filter, Jandy Aquapure 1400 SWG, Polaris 280 w booster, Jandy LXI 4000 heater.
    White plaster, flagstone coping, custom tan tiles with decos on raised spa.
    Pentair lights.
    650 sq ft concrete deck.

  11. Back To Top    #11

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    Re: Very strange moist spots on concrete

    I finally got some time today to try to dry the spots with a hair dryer, I was able to dry the spots completely, but after about 10 mins, the spots came back to about the same size, very strange indeed.
    OH TWINS
    San Juan 8500 gal Fiberglass Pool, Sta-Rite Max-E 1 HP pump, Star-Rite System 3 Cartridge Filter 300 sq. ft,
    Sta-Rite Max-E 200,000 BTU gas heater, Aqua Logic SWG with P-4 panel. Goldline wireless remote control,
    3 Jandy Neverlube Valves with Goldline motorized control, iRobot Verro 500 pool cleaner
    5 Poolstar 1000 LED Lights, LED strip light at waterfall, Prozone Ozonator PZ7 with degasser column,
    Jandy Auto Waterfill, Aquamatic motorized pool cover, Poolbuster Max CC handheld vacuum.

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