Marking out the pool to prepare for and guide the excavation of your inground pool, is an exciting step towards pool ownership. When you see the outline of your pool, all laid out across the backyard, you can't help but smile, and see the whole project more clearly.
This step in the process of building your own inground pool, come after many steps beforehand. At this stage, you have secured all permits, assembled all pool kit materials and supplies and have notified call811, or your local utility line location service, to mark all underground utilities, before you dig.
1. Mark out the Overall Pool Size. Refer to your original plot plan and make sure you match the permitted location. This spot was carefully chosen, considering setbacks, utility locations, easements and other physical right of ways, and also safety, drainage and access factors.
When we dig a pool for an inground pool kit, the hole is going to be 5-6 feet wider and longer than the actual pool size. This is done to give you room to assemble the walls and plumbing, and to pour a concrete collar or footer, around the pool. The walls are backfilled in after inspections are completed.
So, to mark out your Overall Pool Size, add 5 ft. to your pool size. An 18x36 foot rectangle would be dug out at 23x41, plus a large bump out for the step section in the shallow end. This is usually the entrance and exit point for the digging equipment, so you also need a large area for the ramp into the pool.
You can use spray paint, or wooden stakes and strings, or both - to delineate the Overall Pool Size.
How Far Out of Level is your Yard?
Most backyards have some sort of slope to them, even if it's just a few inches. If you have a grade or pitch to your backyard, you'll need to set 1 or more Level Pegs that you can plan the height of your pool walls and pool deck. From these level pegs, you can shoot a transit or use string to find the level, of say, the back patio, and plan your pool to be either the same level, or slightly higher or lower than the patio.
Once you have marked out the overall pool size, you can use a carpenter's level to check the level of the string, as it runs from stake to stake. Tie the string at the same height above the ground on two different pegs, and use a level to see how far off from level they are.
Be sure to plan for storm water run-off around the pool. The pool should always be slightly higher than the surrounding land, and pitch away at 1/4" per foot, or to put it another way, a 4 ft. pool deck should be 1" lower on the outside than on the pool side.
2. Mark out the Pool Floor Shape. The first markings we made were for the Overall Pool Size, and that is the first phase of excavation of an inground pool, is to dig the overall pool width and length, plus 5 feet, down to the wall height of 42 inches. When this is completed, you are done with the part of a pool dig that I call the "Shoe Box".
The topsoil, or the top foot or two of soil is usually kept in a separate pile, or kept on site, for use in backfilling the overdig around the pool walls, and the plumbing trenches.
With the shoe box dug, you can now mark out how to dig the slope from the shallow end to the deep end floor, and the 3 wall slopes in the deep end. It's all done according to the spec plan we include with our pool kits, and stakes and strings are used to direct excavation towards the right measurements.
Good measurements will minimize later work in hand digging in the corners, or shaving down slopes, so that they match each other, all around the deep end.
Assuming that you have a basically rectangular pool, your stakes and strings would look like this.
Think of it as two flat areas, the shallow end floor and the deep end floor, and also the slope from the shallow end to the deep end, and then your three walls in the deep end of the pool. All dead center of the overdig that you created.
There are a total of 10 stakes. An outside 6 stakes, and an internal set of 4 stakes that marks the four corners of the deep end hopper pad, or bottom floor.
The first thing you stake out are the outer stakes that will closely mark the corners of your pool. These are shown here as the red dots. You can find heavy 24" wooden stakes at a home center, in the garden or lumber section. Actually, most corners are actually radius or curved corners, so this stake marks the middle apex of the radius corner wall piece. You should have at least 30" from the walls of the overdig and the stakes.
To find the location for the 4 internal stakes, first, check that all of your 6 outside stakes are fairly level, by running a tight string between all of the stakes, at the same height above the ground. Then, make sure they are square. Check square by taking cross dimensions, or use a transit, which will also be useful for leveling the walls panels.
Then measure in 4 feet from your corner stakes, to find the edges of the 8' wide floor on our example 16'x32' size pool. and place a total of 8 new stakes, in the white circles with red. At the points where they intersect, (gold dots) that is where your deep end corners would be - another 5 feet beneath your feet. The strings are moved when the digging starts, but kept nearby for occasional checks. When you get it finally done, you can set up the strings again and use plumb bob method to accurately locate the four corners. Hand dig and shape if necessary to get the pool floor dug out to the 4 bottom corners, all square and level with each other. Actually, you will overdig it by an inch or two, and cover with a floor material, so there is a little bit of wiggle room, but not much, typical vinyl pool kit floors are less than 1" thick. Then you'll use flat shovels and power tampers to make sure it is flat and even all around on all floor surfaces.
When the dig is complete, you can run strings again, to help you level your floor and define your edges as you apply the floor material. The strings should all be set at the same distance above your finished floor height, an inch or two, and running at the same level angle.
I hope this helps in the installation of your own inground pool. Most pool diggers will have no difficulty reading our spec sheet and digging the proper wall angles to keep hand digging to a minimum.
Use your stakes and strings to start the dig, and to finish the dig, and you'll have an easy time digging and flooring your new inground pool.
SPP Pool Expert