Our family is in the planning stages of a DIY IG 18x36 with an 8' deep end for the end of this summer. I'm targeting the end of the summer because I think I will end up dealing with a water table issue and I'm hoping that the dry summer will work in my favor. I have been monitoring the water table, and find that it's at about the 6-7' mark from finished grade. I "water drilled" a 12' piece of 1.5" ABS pipe vertically into the ground using a garden hose and fittings, then I can check the level with a fishing float and some string. For what it's worth I'm going to be working in soil that appears to have a high sand content.
I've been searching this site (awesome), Google, and YouTube for information of dealing with this issue during the installation of the pool and haven't really found any information that puts my mind at rest... I think I have a couple of viable options, and am asking for suggestions from those with some experience. Here's my list of ideas at the moment:
1.) Overdig the hopper and add a sump - This appears to be the most common solution. Basically overdigging the sump, adding a bucket with lots of holes (basic strainer), gravel to relevel to working height, and a suction line 12" or so below finished grade of the hopper bottom.
Q1.1) What type of pump would be attached to the suction side of this pipe? A self priming trash pump would make sense, but how would you maintain the prime and prevent the pump from running dry once the water is lowered? Any suggestions on a pump? I'm guessing the pump would need to run almost continuously during the build of the pool which might take a month of evenings and weekends (still gotta work)!?
2.) Same Idea as with #1, but installing a sacrificial sump pump. This is possibly a cheap temporarily solution - but I see lots of pitfalls that I'd like to stay away from (premature failure, future service requirements perhaps after a couple of years of inactivity, etc...)
3.) Large Sump - I was thinking of finding a 12-14" piece of pipe (culvert perhaps), and burying it vertically beside the pool, then somehow digging a drainage trench from the gravel in the bottom of the hopper, to the "sump". Then I could add a servicable sumppump which could be pulled and plugged in as needed. I envision a 18" patio stone as a cap, and then interlocking pavers around the pool covering it over until needed.
Q3.1) I can see the installation of this concept being a PITA to excavate, but really effective once installed.
4.) Dewatering - I know I can use the "well boring" idea that I used to sink the 1.5" ABS pipe (for my DIY ground-water meter) into the area around the planned dig site. I think I could use this technique to do say 4-6 of them around the overdig, then add some type of foot valve, or screen, or something to the bottoms. Then I could connect them together, and use some type of self priming pump to temporarily lower the water level. Once this was in place it would be easy to add idea#1 to the hopper for future requirements.
Q4.1) Same as Q1.1 really - What type of pump, and what prevents it from burning out once the water level is lowered to the point where the suction starts to possibly pull air break the prime?
5.) - I'd love to hear more ideas!
If you've made it this far, thanks for taking the time to read my ramblings
Many thanks to those who have previously posted information about their installations - the information has been invaluable!