When you build your own inground pool, there are usually one or two difficulties that you run into, one of these usually being the weather. Heavy rainstorms during excavation can cause some small erosion to your pool shape, if you get hit before you get the floor material (vermiculite or sand/concrete mix) laid down.
A much less common occurrence is to hit ground water while digging the deep end. This can happen if your pool location is in a low depression as compared to the surrounding land, or if located beneath a hillside of any size. It can also happen after heavy rainstorms raise the water table.
In most cases, the water will subside, so my first advice is to just see if the water will recede back into the earth in a day or two, and then you can proceed with installing the pool floor, the liner, and adding water to fill the pool.
In some cases, the water won't subside - if it keeps raining, or if the pool deep end is located within the water table. Start with a small submersible pump (you can rent one for $15/day), and connect 100' of garden hose to run the hose away from the deep end as far as possible. Plug in the pump, and pump out the water in the deep end.
INGROUND VINYL POOL DEWATERING METHODS
If precious days are passing, and weepers and leakers are continuing to fill the deep end area faster than you can pump it out, here's what you do. Get on the phone, or online and place an order for 2-3 yards of the cheapest gravel, usually #57 bluestone. Jump back in the track hoe, or just start hand digging, and overdig the deep end hopper by 2'. So, if you have an 8' deep end, overdig it to 10', and then dig a narrow trench from the now deeper deep end floor, up the side wall, and out of the pool, just underneath the pool wall.
OPTION ONE: Place a main drain pot in the lowest spot of the floor, and connect a one way check valve with a short piece of PVC pipe. Then glue on a long section of flexible pipe that comes up to ground level. There you can connect your pool filter pump, with a male adapter. Fill the pipe and pump with water, and use it to dewater underneath the pool, until you get it full of water.
OPTION TWO: Buy a cheap submersible pump with a long cord and place it in the lowest part of the overdug deep end. Cover with a few feet of gravel and run the discharge (garden) hose and the power cord up the sidewall trench and underneath the pool wall. The pump is abandoned underneath the pool after the pool is filled with water. It could be left in place, for pools with high water tables, but the motor will likely fail within a few years.
OPTION THREE: For a more permanent solution, for pools that are very close and level with large bodies of water, or located in a flood plain. Place a main drain pot in the deepest part of the overdig, and connect a pipe that drains to a sump pump well, or a plastic vertical cylinder that is accessed at ground level. Inside the well, an automatic sump pump is placed, which will turn on when water in the well cylinder raises the float sensor.
OPTION FOUR: Raise the pool! That is, bring in enough dirt, probably 20 yds or more of fill dirt, and raise up the earth in the pool and around the pool. This can only be done if you haven't already poured the concrete collar around the pool walls. This is a good solution for installations where you know water will be encountered; pools on a shoreline, in a floodplain, high water table, or for a location that receives a lot of storm water run-off. Steps can lead up to the pool deck, which can be 1-4 feet above the surrounding area.
TEMPORARY POOL DEWATERING - OR PERMANENT?
After the pool is filled with water on top of your 2" floor base material, that's heavy enough to keep water back, and your dewatering solution, so useful during construction, will no longer be needed, and the pipe or hose is left buried underneath the pool.
In a few cases however, a liner can 'float', when water gets underneath the liner, and causes a large visible bulge, usually after periods of very heavy rain. If you think that this may be a possibility, due to a poor pool location, high water table, excessive water runoff or bad soil types...you may want to have the ability to dewater underneath the liner, should your liner ever 'bulge'. Options 1 and 3 above are better to use for a permanent pool dewatering solution, but can be installed after a pool is already built, if needed.
If you encounter water when you dig, do not worry - the SPP experts are here to help you with advice tailored to your situation. I've been involved in over 1000 pool builds, and we hit water about 10% of the time, but a true pool dewatering system is needed only less than 5% of the time.
One last piece of advice. Pay attention to the long range weather forecast before you begin construction. If you have some flexibility in your schedule, you may avoid hitting water if you dig your pool during dry periods of the year, and when the 10 day forecast looks mostly sunny. If you can get a week of fairly dry weather, you will have less chance of hitting water.
SPP Pool Expert