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Thread: Hitting the Water Table

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    Hitting the Water Table

    We are preparing to start a new pool project in the next several weeks. We live in northern Ohio in a rather low level area. I am concerned with hitting the water table when we start our install. Is hitting the water table a big deal? We will have a vermiculite bottom and I am really hoping that the pool will be able to last for more than a few years. The deep end of our pool is going to be 8 feet so I am quite sure we will run into water. We are considering making the deep end shallower to avoid this. Just want to avoid future issues once the job is all done.
    Scott

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    Welcome. If you do a gunite pool, other than the problems of water during construction, you should be ok. If you do a vinyl liner pool, you'll have to sink wellpoints around the pool to keep the water pumped out away from the pool so your liner doesn't float. Probably the same with fibreglass.

    I would discuss that with a VERY knowledgeable pool builder before I sign a contract and made sure I was comfortable with his approach. It's doable but not without making some provisions for it.
    Dave S. - Forum owner
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    Vader, welcome to TFP - I'm on my way to bed right now, can you hold off til tomorrow for my input? -- Dave has covered most of it, but I've got a couple of particulars in mind to tell you about - we do pools like yours a couple of times each year.

    I hope the delay in my being able to concentrate on my answer doesn't 'put you off' of this site but I want to be able to devote my attention to it
    Luv& Luk
    -Ted

    Having done construction and service for 4 pool companies in 4 states starting in 1988, what I know about pools could fill a couple of books - what I don't know could fill a couple of libraries :-D

    POOL SCHOOL, TF Testkits, Jason's Pool Calculator, CYA vs. cl chart, (Just a few DARNED handy links!)

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    [quote="duraleigh"]Welcome. If you do a gunite pool, other than the problems of water during construction, you should be ok. If you do a vinyl liner pool, you'll have to sink wellpoints around the pool to keep the water pumped out away from the pool so your liner doesn't float. Probably the same with fibreglass.

    We are using a vinyl liner. What exactly will the wellpoints do? I know the installer talked about putting down gravel and making sure to pump out the water so he can do the bottom in vermiculite, but will that be enough?
    Scott

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    but will that be enough?
    Not in my opinion. The water must be constantly kept away from a vinyl lined pool. If not, the pressure is equalized on both sides of the liner and your liner will float freely in the pool with nothing to hold it tightly against the sides. Some type of permanent water removal system must be used to keep the liner snug.

    Wellpoints are used to place a sump pump deep along beside the pool and remove ground water next to the pool.
    Dave S. - Forum owner
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    TFTestkits , PoolMath , Pool School

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    Just wondering..... do you have a basement with a sump pump? How often does the sump pump run? Are there other inground pools near you?

    Your going to have to rely on your PB. If he is local, he should know what he is doing.
    Hotrod30

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    How much slope is there in the area?
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    I just dug my pool in South Louisiana in rainy February. My property is 28 ft above sea level and I'm surrounded by rice fields and crawfish ponds. We dug down 9' and never hit water. I was very surprised, but nothing but hard clay all the way down. We excavated with the plan, that if we hit uncontrollable water early on, the 8' deep end would become a 5' water volleyball court.
    Fortune favors the well prepared

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    Freeform 24' x 38' IG gunite. 3 1/2' to 8' deep. 28,500 gallons. AutoPilot Total Control SWCG. Pentair Intelliflo VF. Pentair CCP520 cartridge filter. Colorlogic LED lights. Tahoe Blue Diamond Brite. 1200 sq ft stamped concrete deck.
    More details as they happen...

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    [quote="Hotrod30"]Just wondering..... do you have a basement with a sump pump? How often does the sump pump run? Are there other inground pools near you?quote]

    We do have a basement with a sump pump and it is running about every 15 to 20 min in the Spring (now) and much less as the summer and fall hit. There is an inground pool across the street, but they are at a higher elevation than we are.
    Scott

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    Quote Originally Posted by JohnT
    How much slope is there in the area?
    Our development is fairly flat. Across the street from us is another development that has a bit higher ground. We have a Spring fed lake about 175 yards away from where we would be digging for our pool.
    Scott

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    There are ways to deal with installing a pool in an area with a very high water table. It is extra work, but isn't usually all that much more expensive. Make sure you work with a builder that is aware of the risks and confident they know how to deal with it.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Vader,

    I live in Warren. We don't have any real flooding issues in out neighborhood.

    My inground was built with a vermiculite botton and vinyl liner. Also, the PB installed drainage pipe all around the pool that goes to a well-sump that has a pump pump at the bottom. I just checked it yesterday and some water at the very bottom.

    This set-up should work for you. Just my .02.
    25,000 gal IG Utopia pool/Raypack gas heater/BBB

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    Sorry I couldn't type this last night --

    As I said, we encounter this problem a few times each summer on new IG liner pools. You can dig a trench all the way around the pool and fill it with drainage pipe and gravel - but that only works to divert water from the pool area and the water needs to have a lower area to go to (which doesn't sound like your case) You can install permanent well points (as Dave suggested) to be able to pump the water away from the pool, but you've gotta get the water far enough away, and preferably to a lower area.

    What we do 90% of the time is overdig the pool bottom by 2 -3' and add gravel to bring it back up to grade. We then install a sump pump which runs constantly until the liner is installed (we leave a hole in the vermiculite, which gets patched with hydrolic cement minutes before the water starts filling the pool). Speed is key! (I lied before - we turn off the pump while prepping the floor for the liner to see how quickly the water is rising) We always set the liner with trucked in water - not too many garden hoses can provide a quick enough fill when the ground water is rising and threatening to push the liner around. We wait until the water guy is ready to start pumping, then remove the sump pump, patch the hole it left, finish installing the liner in the deep end, fire up the vacs, work out any wrinkles and THEN let the water flow!

    A major consideration is at what level you hit the ground water - if it's within ~ 3" of the proposed bottom, all's fine - much more than that and it's time to rethink your pool depth (ie. turn a diving pool into a sport pool)

    I hope this was worth the wait - if you have further questions on what I've said, just ask :thumright:
    Luv& Luk
    -Ted

    Having done construction and service for 4 pool companies in 4 states starting in 1988, what I know about pools could fill a couple of books - what I don't know could fill a couple of libraries :-D

    POOL SCHOOL, TF Testkits, Jason's Pool Calculator, CYA vs. cl chart, (Just a few DARNED handy links!)

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    Quote Originally Posted by ideliver
    Vader,

    I live in Warren. We don't have any real flooding issues in out neighborhood.

    My inground was built with a vermiculite botton and vinyl liner. Also, the PB installed drainage pipe all around the pool that goes to a well-sump that has a pump pump at the bottom. I just checked it yesterday and some water at the very bottom.

    This set-up should work for you. Just my .02.
    What company did you use? Warren is not to far from us in Akron. We are looking at Homestead in Salem and they will let us use any PB we want.
    Scott

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    [quote="waste"]
    A major consideration is at what level you hit the ground water - if it's within ~ 3" of the proposed bottom, all's fine - much more than that and it's time to rethink your pool depth (ie. turn a diving pool into a sport pool)

    Could you explain what this means?

    Also, what if once the pool is in, the water table level goes up? Will a vermiculite bottom be able to stand the test of time and water from below if we have a real wet spring later? quote]
    Scott

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    Scott, always happy to clarify anything I've said 8)

    I'll set up a hypothetical situation for this -- you want an 8' deep pool so you can have a diving board, but while digging they hit water at ~7' 10" -- in this case you could run the pump as I said and still be able to install the floor and liner 'trouble free' . However, if you hit water at 6' 6" you would want to either install a 'well point' (a gravel filled hole next to the pool with a sump pump in it deeper than the bottom of the pool, to keep the water at bay ~constantly) or decide that it's not worth installing the well point and pump and go with a shallower pool (a 'sport pool' is one in which the floor level is shallow enough for an adult to stand in at it's deepest - usually 6' max) which means you loose the diving option

    Usually (~) the pool is installed when the water table is at ~ it's highest (your PB should! know the water tables for the area), and once the pool is in and full, the weight of the pool water is enough to keep the liner from being 'pushed around' by ground water - if it was only a few inches above the floor when the pool was installed - this may mean that you don't drain any water out when winterizing the pool (it's not muchharder to winterize a full pool, but a lot wetter for whoever is doing the winterizing ) However, if you ever experience 'record breaking' rains - the well point will help to keep the ground water from floating the liner.

    The vermiculite is, by it's nature, solid yet porous - water can pass through it easily-- however, if too much water is continually passing through it, the cement in it will wash out leaving you with nothing but mud and 'mushy' vermiculite.
    Luv& Luk
    -Ted

    Having done construction and service for 4 pool companies in 4 states starting in 1988, what I know about pools could fill a couple of books - what I don't know could fill a couple of libraries :-D

    POOL SCHOOL, TF Testkits, Jason's Pool Calculator, CYA vs. cl chart, (Just a few DARNED handy links!)

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    I live in an area with a lake and many streams and as such our water table is very shallow. When we put an addition on our house we hit an underground stream. Our pool is of similar design as you are proposing. The PB built a gravel drywell under the deep end of the pool and it is piped to the main pump. I can valve the pump to waste and open this line to use the main pump to pump out and water.

    After the initial build the only time you have a problem is if the water level in the pool drops, otherwise it is not really an issue. Anytime the liner is a little loose at the corners in the shallow end I just pump for a few minutes and everything is fine.
    20x40 IG vinyl, heatpump and solar and 3 siberian huskies, 10kw PV solar electric system. Nikon Photographer D800e dSLR.

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    The trouble with a dry well under the deep end is you have to watch how fast you pump the water out. If the ground water level is high, and you pump it from under the deep end fast, you could cause a vacuum and cause the water by the steel walls to go to the dry well fast. In the rush it could cause the sand wall(s) in the hopper to collapse.

    I hope I explained that clearly.

    My pool.... 1992. replacing the liner. Pool company hooked up a large mud sucker to the dry well line and caused one hopper wall to collapse.
    Hotrod30

    20 X 40 foot vinyl Borates and Salt Pool
    Rolachem Chlorine Feeder
    Hayward 27 inch sand filter with 80 lbs of pea gravel
    Jacuzzi Splash Pak SP55 DE filter in parallel
    Pentair VF3050 pump

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