Leach Field Rock Calculator
Find out how much rock a leach line needs. Enter your trenches, trench width and rock depths, and get cubic yards and tons to order. The pipe is subtracted for you.
Permit first: Leach fields need a county permit and an approved design; use the rock size and trench dimensions your county specifies.
Starting values are common leach line dimensions. Replace them with the numbers on your approved plan.
Order quantity is rounded up to the nearest half yard, the size of one loader scoop. Tons are the true weight of the rock your trenches hold.
Permit first: Leach fields need a county permit and an approved design; use the rock size and trench dimensions your county specifies.
Natural river stone, not washed. County codes ask for clean rock and Los Angeles County requires washed rock with a supplier statement, so confirm with your county inspector that unwashed rock is accepted before you order.
Visalia River Rock for leach lines
For leach lines we offer one rock: the 1" - 1-1/2" grade, which sits inside the 3/4 to 2-1/2 inch range in the county rules. Natural river stone, not washed. County codes ask for clean rock and Los Angeles County requires washed rock with a supplier statement, so confirm with your county inspector that unwashed rock is accepted before you order.
How the leach line rock is calculated
Each trench is filled with rock below the pipe, around the pipe, and over the pipe. The calculator multiplies the trench width by the full rock depth, takes out the round pipe, and multiplies by the trench length and number of lines.
- Rock depth = rock below pipe + pipe diameter + rock cover over pipe
- Cross section = trench width x rock depth, minus the pipe (pi x diameter x diameter / 4)
- Cubic feet = cross section x length x number of lines, then divided by 27 for cubic yards
- Tons use the same river rock density as the rest of our calculators (about 1.45 tons per cubic yard)
Starting values follow Tulare, Kern and Fresno County standards: an 18 to 36 inch trench, 12 inches of rock under the pipe, 2 inches over the pipe, and clean 3/4 to 2-1/2 inch rock. Your own county and your approved design decide the real numbers, so use those.
Leach field rock questions
How much gravel do I need for a leach field?
It depends on the length and number of trenches. One 100 foot line, 24 inches wide, with 12 inches of rock below a 4 inch pipe and 2 inches over it, takes about 10.8 cubic yards, or roughly 15.6 tons of river rock. Enter your own trench sizes above for the exact figure.
What size rock does a leach line need?
County codes in Tulare, Kern and Fresno call for clean, washed stone or gravel from 3/4 inch to 2-1/2 inches. The codes do not specify a shape, so crushed or rounded rock both qualify. What fails inspection is fines: dirt, dust and sand mixed into the load. Our Visalia River Rock in the 1" - 1-1/2" grade fits that size range, but it is natural stone and is not washed, so confirm with your own county inspector that unwashed rock is accepted before you order.
Is Visalia River Rock washed?
No. Visalia River Rock is natural river stone and is not washed. The 1" - 1-1/2" grade fits the 3/4 to 2-1/2 inch size range, but county codes ask for clean rock and Los Angeles County requires washed rock with a supplier statement. Confirm with your county inspector that unwashed rock is accepted before you order, and ask us for a sample to show them.
How many tons are in a cubic yard of river rock?
About 1.45 tons. River rock weighs roughly 2,900 pounds per cubic yard, which is the density this calculator uses.
Why does the calculator subtract the pipe?
The pipe takes up space in the trench where rock does not go. For a 4 inch pipe the difference is small, but on long runs it adds up to a fraction of a yard.
How much extra should I order?
Add about 10 percent for settling and uneven trench bottoms. Turn on the Add 10% box in the calculator to include it. The order quantity is already rounded up to the next half yard.
Do you deliver river rock for leach fields?
Yes. We deliver by the truckload from our California yards. Add the rock to your cart to see delivery options for your ZIP code, or call (800) 215-7372 for a large job.