Gravel Around Pools

Gravel is used in many places around pools.

Where is Gravel Used Around Pools?

Gravel is used for backfill for pools. Gravel is permeable and helps in drainage in the areas it is used. Gravel packs very well and is preferable to sand or dirt. Gravel is easier to use then sand that needs to be washed in or dirt that needs to sit for weeks or months to reach a desired compaction rate.

Best practice is dirt out once its disturbed and gravel backfill as necessary. Excess dirt can be used for grading, otherwise its trucked out.

Gravel is also used in well points

What Are the Different Types of Gravel?

There are different types and sizes or gravel:

• 89 stone is a small size used as the base to set a pool on and to backfill the step and seating areas. 89 stone can fill tight areas that may leave a void area of material.
• 57 stone is about a half inch in size and is used to backfill the side walls of a pool. 57 stone works well locking together for good compaction when it is dropped into the overdig area around the pool. Its 95% compacted out of the bucket. A light hand tamp or plate compactor and you are good.

Other types of rock used around pools are:

3/4 River Rock

• 3/4" clean (what everyone calls "gravel" in some spots (mainly for drainage in areas you cannot see)
• 3/8" grey pea gravel in some areas - like under the swing set.
• 3/8" yellow pea gravel around some trees
• 2" egg rock around the pool. It is large enough to stay in place, but it nests well. The rounded edges make it easy to pull any stray weeds that get into it.
• Pea gravel is most often recommended for the base of fiberglass pools. Get a tamper in there on the base material, and compact in lifts.
• Pea gravel gets everywhere - it is too small to put around the pool. It gets knocked out of wherever you put it too easily. It works great under a swing set, because a good layer of pea gravel provides a cushioned surface for around swings and play structures.
• Eastern Sunrise is pretty, it is it like volcanic rock. It is unstable to walk on, and dogs hates it (it hurts paws). It is also a pain to weed in (because it is so sharp)
• Crusher run is stone dust and 57 stone mixed. Crusher dust is stone dust that's better than sand. Sand is round tiny marbles and will wash with rain. Stone dust or concrete sand looks like rice under a magnifying glass it locks together and wont wash easily.

Typically a crushed stone is preferred for structural purposes and a round stone is preferred for drainage and aesthetic purposes. The sharp angles of crushed stone will lock together better for more stability.

When buying stone, bulk is SO much cheaper than bags. If you have a need for any sort of quantity of stone, look into bulk delivery. Or, even better, if you can get it yourself, its even cheaper. Just be careful, stone is heavy.

Why is 57 Stone Named 57?

Because it has both AASHTO size #5 & size #7 rocks. Probably doesn't help explain it much, but trying to understand or explain the naming conventions for AASHTO aggregate sizing is an exercise in frustration.

How Much Gravel Will You Need?

Try some of these calculators:

• Material Calculator
• Aggregate Calculator
• Materials Estimating

Does Gravel Need to be Compacted?

Any gravel you put down that is not clean will need to be compacted with a plate. Only sharp angular rock like #57 known as 3/4 clean can be put down without a machine compact. Anything with mixed sizes and fines mixed in like road base will settle if not compacted.

Gravel in Vinyl In-Ground Pool Builds

• Raise the bottom using clean 3/4 gravel.
• Use it to fine tune the bottom and then use 1/4 stone to fine tune the panels.
• Have them dump close to the pool and use the bucket to bring it in. Cover the whole shallow end and shelf and use it for the backfill of wall panels.
• Don't use concrete to backfill.
• If you have clay use a geotextile fabric on top of your compacted sub base then add gravel base for your decking.

Gravel for Drainage Around a Pool

• If a concrete pool, put perforated hard pipe around the base and backfill with clean gravel then drop to a 10" sump pit and pipe it underground.
• Don't forget to run electric to the pit you do not want to be running extension cords. 1/3 hp is enough for a drainage pit you can play with the height of pump in pit later to keep it from running 24/7.
• Location doesn't matter. The drainage pipe will bring water to where you want it.
• Do not use corrugated flex pipe no matter what. You should only use SDR rated drain pipe.
• Wrap the base dirt and go up the wall with a woven septic type fabric and then fold it over to the pool wall a foot or more up on the gravel. Over time the fines in the soil will migrate and 10yrs down the road the voids in gravel will be filled with silt and not perc as well. If you have sand it will not be as bad as dirt but will happen.
• When you protect the drainage pipe you protect its gravel too which is just as important as pipe

Gravel Around Fiberglass Pools

Large gravel is not to be used against a fiberglass shell. Gravel is a loose term here, There are MANY grades of stone. Pea or similar is the proper base and backfill material even down to turkey grit gravel is fine for the base as this area can and will be mechanically compacted.

The sides need angular like 1/4" up to 3/8 max and some even use course sand and grit mixes. All fine to use. When we talk about clean stone or #57 gravel etc we imply we are backfilling against a steel wall or concrete pool not fiberglass

Backfilling PVC Pipe Trenches

You can use paver base that has rocks and fines mixed in together.

You don't want clean gravel in trenches, it needs to have mixed fines. With gravel in trenches, the voids can hold water and freeze if your in a frost climate.

It can be cheaper to have a landscape place drop a yard of bulk road base or paver base if you need more than 10 bags.

Compacting Fill and Using Gravel

The issue with compacting fill, of any kind, is that there is a sweet spot of moisture content where it will compact to its maximum density. If the soil is not at that moisture content, you can compact it until the cows come home, and it will still settle once it gets to that water content.

Some soils are more forgiving. You can get 95% maximum compaction (what you usually shoot for) over a wide range of moisture content. Other soils are a lot less forgiving, and have to be really close to the correct moisture content.

So how do you know this magic water content? You take your multiple soil samples to the lab, and you run Proctor tests on them (you can do it in field too, but it is not exactly fun), so you can develop what is call a family of Proctor curves.

Then when compacting in the field, you do in situ compaction testing, either by using an Ottawa Sand Cone, or a Nuclear Soil Densometer. Clearly your average homeowner with a Home Depot Rental plate compactor is not going to do this, so that is why we say you cannot use fill. You *could* if you hired an engineer, and an earthworks contractor that knows how to work with fill for foundations, but that is not a cheap route.

If you need to fill in a bit you can get something called Quarry Process, QP, Crusher Run, DGA, or Densely Graded Aggregate, depending on what neck of the woods you live in and what the locals call it. It is a blend of 3/4" stone down to rock dust (and everything in between - hence the Densely Graded part),

Crusher Run is the "run of the crusher" when they run the rock at the quarry through the crusher, it's not "Crush and Run". It is a VERY forgiving material with a very flat Proctor curve (meaning you don't have to super dial in the moisture content).

57 stone is clean stone that passes a #57 sieve. It's about 1" in diameter with no fines. It is great for drainage, or gravel drives, but not really the best for under a pool.

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