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Thread: Old Gunite Pool - Time to resurface?

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    Old Gunite Pool - Time to resurface?

    Hey everyone,

    About 4 years ago I bought a 1940's home in foreclosure with a pool that had been allowed to turn into a disaster. I have managed to get the pool cleaned up and functioning for the last few summers, but I'm continually having problems with algae coming back with ANY weakness in chemical levels (and sometimes even when things seem perfect to me).

    I will say this pool has stains in it from when a previous owner let it go and then tried to clean it up - so even when the water is perfect it doesn't look great. I'm thinking it must be a 30-40 year old pool.

    I noticed this last summer that the pool has nasty breaks/flaking/digs in the gunite where algae is growing and I just can't scrub it out when I'm cleaning - so I don't think I'm ever getting rid of all of it.

    At this point I'm very frustrated with trying to keep this thing clean the fact that it never seems to get totally clean and reasonable to manage like I know it should be.

    Are there any options to clean up the gunite and get this thing back in shape without re-surfacing the entire thing? I don't care if it looks perfect, but dealing with this algae problem has got to stop.

    Thanks for any advice.

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    JasonLion's Avatar
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    Re: Old Gunite Pool - Time to resurface?

    Welcome to TFP!

    You almost certainly have a layer of pool plaster on top of the gunite. Gunite is very rough and not completely waterproof, so it is normally coated with a special kind of waterproof plaster.

    The plaster can be patched, though it is something of a project, including draining the pool below the deepest area that needs work, and it will never match up visually. Plaster tends to last ten to twenty years, after which it should be redone. If the damage is at all extensive, repairing it will cost nearly as much, or more, than getting new plaster.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Re: Old Gunite Pool - Time to resurface?

    That's good info thank you. Do you have any idea how much that costs? Also, I had someone at a pool store here tell me that I could "float" my pool if I drained the water out. Is there any way around this?

    I also think I may have realized why the algae is growing even with a good chlorine level. My CYA is actually quite low - I've read this can keep the chlorine from sanitizing because it just goes off to fast...does that sound accurate?

    Thanks again for the input!

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    Re: Old Gunite Pool - Time to resurface?

    Low CYA means the chlorine is more readily consumed by UV from the sun. Low CYA will not keep the chlorine from sanitizing, nor from oxidizing the algae. It could let the chlorine level drop to 0 by being consumed by the sun, though. If you're sure the chlorine level stays "good" all day, low CYA will not cause an algae problem. It will just cause you to use more chlorine each day since more is consumed by the sun.

    Do you have a test kit? What are the numbers at the end of the day?
    Outdoor 14,000 gallon IG plaster pool built in 2000 with spillover spa, 2 hp WhisperFlo pump with MagneTek motor, Sta-Rite cartridge pool filter with 300 ft2 filtration area and 0.33 gpm/ft2 filtration rate, Aquabot Rapids 4WD robotic pool cleaner, Raypak digital gas heater, and Intermatic mechanical timer located in the Dallas-Fort Worth metroplex

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    Re: Old Gunite Pool - Time to resurface?

    I just use the strips to monitor things. What I'm noticing though is that even though chlorine and free chlorine are staying in acceptable levels, I'm still seeing algae grow/spread (albeit slowly).

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    linen's Avatar
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    Re: Old Gunite Pool - Time to resurface?

    Welcome to tfp, tmcd

    Quote Originally Posted by tmcd
    Also, I had someone at a pool store here tell me that I could "float" my pool if I drained the water out. Is there any way around this?
    Yes, this is a real concern, especially where the ground water level is high. Was that I have heard to deal with this are, dry well points around the pool, adding a hydrostatic valve in the bottom drain, and I have even heard of purposefully putting holes in the gunnite shell that get filled when the new plaster is put on.

    Quote Originally Posted by tmcd
    I just use the strips to monitor things. What I'm noticing though is that even though chlorine and free chlorine are staying in acceptable levels, I'm still seeing algae grow/spread (albeit slowly).
    Test strips are very unreliable for almost all test parameters (ph seems to be the only test that strips get more right than wrong in my experience). In fact, if your cya value of 20 came from a strip, I would bet that is not your real value.
    TFP Expert who uses Pool School and my TF100 test kit along with PoolMath for my: Round 11K gallon AGP with deep end, 20" sand filter, Matrix 1hp 2spd, 6 2ftX20ft solar panels (and solar cover!), Intex SWCG (copper bars disconnected) and a Rubadub hot tub (chlorine). The SLAM process is not finished until: 1. CC < 0.5 ppm, 2. An OCLT < 1.0 ppm and, 3. The water is crystal clear.

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    pwrstrk's Avatar
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    Old Gunite Pool - Time to resurface?

    Quote Originally Posted by tmcd
    I just use the strips to monitor things. What I'm noticing though is that even though chlorine and free chlorine are staying in acceptable levels, I'm still seeing algae grow/spread (albeit slowly).
    I would suggest you look into getting one of the recommended test kits. I use the TF 100. Order the TF100 with the XL option. It's a must have for proper pool maintaince. Those test strips are worthless.

    Test kit can be gotten at TFTestkits.net.

    If you have visible algae you need to SALM the pool pool-school/shocking_your_pool
    You won't be able to do the SLAM process without a good test kit.
    Jeff
    24'x54" AG Morada RTR (by wilbar) 13'500 gal. Hayward Powerflo Matrix 1hp 2 speed. Hayward Perflex EC65 DE filter.

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    Re: Old Gunite Pool - Time to resurface?

    Ok thanks all. Following up again on the cost of resurfacing - I've read online general estimates of 7-10k(YIKES!). Does this sound right/is this something I could potentially tackle myself? (IE is it more about labor hours than great knowledge/skill).

    Thanks again

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    Re: Old Gunite Pool - Time to resurface?

    Those estimates sound high. How big is the pool?

    A re-plaster is not a straightforward do-it-yourself project, no. See if you can find one of the YouTube videos showing the plastering process; that should give you some insight. For a re-plaster, I think there is the added non-trivial step of removing the existing plaster.
    Outdoor 14,000 gallon IG plaster pool built in 2000 with spillover spa, 2 hp WhisperFlo pump with MagneTek motor, Sta-Rite cartridge pool filter with 300 ft2 filtration area and 0.33 gpm/ft2 filtration rate, Aquabot Rapids 4WD robotic pool cleaner, Raypak digital gas heater, and Intermatic mechanical timer located in the Dallas-Fort Worth metroplex

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