Ordering Stone and Materials for a Dry Well

Ordering for a dry well starts with one rule: the stone order equals the gross pit volume in loose cubic yards. Bulk stone ships with its voids included, so the voids ride along with the load. Everything after that is unit conversion, a small waste allowance, and delivery logistics.

How much stone does a dry well need?

Measure the pit, convert the volume to cubic yards, and order that many loose yards plus about 10% for spillage and settling. A pit 6 ft long, 6 ft wide, and 6 ft deep holds 216 ft3. Divide by 27 and the order is 8.00 yd3 of loose stone; 8.80 yd3 with the 10% allowance, which rounds up to a 9 yd3 order.

Never shrink this number by the void ratio. The stone and soil guide explains why storage is only 30 to 40 percent of the pit; the order is still the full 216 ft3 of loose stone.

How do you turn pit measurements into an order?

1. Measure length, width, and depth in feet at several points, or diameter and depth for a round pit.
2. Rectangular volume is length × width × depth. Cylindrical volume is π × radius² × depth.
3. Divide by 27 to get cubic yards.
4. Ask the supplier whether the order runs by the yard or by the ton.
5. If by the ton, multiply the cubic yards by the product's weight per cubic yard.
6. Add about 10% and round up to the supplier's selling increment.

How do tons and cubic yards differ?

A cubic yard measures volume: 27 ft3, the space the stone occupies. A US ton measures weight: 2,000 lb. Converting between them needs the stone's weight per cubic yard, which varies with rock type, particle size, and moisture.

Dry gravel and crushed stone commonly run 1.2 to 1.7 tons per cubic yard. A figure of 1.4 t/yd3 works for rough planning, and contractors often use 2,700 lb per cubic yard for crushed stone. For the final order, use the supplier's weight for the actual product delivered.

Worked example with the 6 ft pit: 8 yd3 × 1.4 = 11.2 tons; with the 10% allowance that is 12.32, so order 12.5 tons. With the 2,700 lb figure: 8 × 2,700 = 21,600 lb = 10.8 tons; with 10% that is 11.88, so order 12 tons. The two routes agree within a ton, which is the right size of check before calling the supplier.

Common pit sizes and their orders

The ton figures are approximate. Confirm the product's weight per cubic yard with the supplier before the final order.

What if the job is small enough for bags?

One cubic yard equals 54 bags of 0.5 ft3 stone. The 4 ft diameter cylinder in the table (2.33 yd3) would need about 126 bags. Bagged stone costs far more per yard than bulk, so bags suit small top-ups and repairs, not a full pit.

How much geotextile fabric and pipe should you order?

Fabric lines the pit bottom and sides before the stone goes in. Buy enough to cover the bottom plus the perimeter multiplied by the depth, with 6 to 12 in of overlap at every seam and extra to fold over the top after filling. Check the roll's width and length with the supplier before cutting.

Pipe connects the water source to the well. Order 4 in diameter drain pipe, solid PVC or corrugated, in the trench length plus about 2 ft for connections and cuts. Run it with a minimum slope of 1/8 in per foot toward the well.

What should the delivery truck have waiting for it?

Give the truck 12 to 14 ft of clear width, clear overhead lines, and firm ground that will not trap a loaded axle. Mark the drop area before the truck arrives and keep it close to the pit, because every extra wheelbarrow carry slows the job. Ask about tailgate spreading at order time; drivers spread only where the site allows it.

Have the stone arrive after the pit is dug, lined, and measured. Stone delivered early gets moved twice.

What mistakes change the order?

• Shrinking the stone order by the void ratio. The bulk load already includes the voids.
• Converting yards to tons with a generic figure for a large order instead of the supplier's product weight.
• Skipping the 10% allowance, then running short on the last wheelbarrow.
• Rounding down to a selling increment instead of up.
• Buying bagged stone for a full pit and paying the bagged premium per yard.
• Ordering fabric short of the seam overlap and the top fold.
• Ordering pipe in the exact trench length with nothing left for connections.
• Booking delivery without checking truck access, then paying for a second trip.

Safety and professional scope

Contact 811 a few business days before digging and wait for buried utilities to be marked. Keep spoil and equipment away from the pit edge and take measurements from a safe position. Sizing the well for a storm (runoff area, rainfall, percolation) is a separate design step for qualified people. This page covers the material order only.