How to Find the Private Lines a Utility Locate Will Not Mark
Why this matters
An 811 locate marks what the utilities own, and in most yards they own almost nothing past the meter. The garage feeder, irrigation, landscape lighting, propane line, pool bonding ring and septic sewer all belong to the homeowner, and the locate crew walks past them. A crew that treats a clean locate as a clean yard is the crew that cuts the garage feeder at post hole nine. This card is the procedure for finding what the locate left out. The locate itself is covered in The Utility Locate: Before You Dig; this card starts where that one stops.
Safety first
- If you strike anything with gas in it (the smell of rotten eggs, hissing, blowing dirt): stop the auger or digger and leave it where it is, everyone walks away upwind, no engines started, no switches, no phone used near the hole. From a distance, call 911 and the gas utility or propane supplier. Do not try to plug, crimp or bury the line.
- If you strike a wire: let go of the tool if you can do so without touching anything else, keep everyone at least a truck length away from the tool and the hole, and treat the tool, the soil around it and anything touching it as energized. Call the electric utility if it could be their line, or the homeowner's electrician for a private feeder, and keep people away until the circuit is proved off.
- If you strike a sewer or septic line: keep people and pets clear of anything wet, gloves on before touching soil or pipe, and ask the household to stop running water until the septic or plumbing contractor arrives.
The yard, drawn with only the lines 811 will not mark
STREET (gas and power marked to the meters only)
===================================================
| |
| water service | gas service
| (curb stop->house |
| may be private) | +--------- HOUSE ----------+
| +-->| meter cleanout |
+------------------------>| main | |
+--------------|-----------+
irrigation garage building \ sewer
valve box feeder sewer \ 4 in
[V] - - - heads (UF or to tank \
| - - - - laterals conduit) [TANK]
| \ |
| lights ~~~~~~ \ DETACHED | to field
| low-voltage cable +-> GARAGE [DRAINFIELD]
|
| PROPANE TANK ===== yellow poly line ====> house
|
+---- POOL: bonding ring 18-24 in out, few in down
+ feeder and pipes to EQUIPMENT PAD
Every line in that drawing is a real thing in a real yard, and none of it gets paint from the public locate.
The procedure
1. Ask the customer before you look at anything
Do it because the homeowner, or the previous owner's paperwork, knows where most of these lines run, and a two-minute conversation is cheaper than any locating method.
Ask about each one by name, because "is there anything buried?" gets "no" from people who forgot the garage has power: power to a garage or shed, irrigation, landscape lights, propane (and whether it feeds a pool heater, grill or generator), a pool or hot tub, septic or sewer, a well, an electric gate, an invisible pet fence, buried downspout drains. Ask for a survey, septic permit drawing or pool permit set.
What breaks if skipped: you read clues without a list, and a lone conduit stub means nothing to you.
2. Read the visible clues from the house outward
Do it because every buried line has to come out of the ground somewhere, and the place it surfaces tells you its direction.
Walk the house perimeter first, then the yard. Look for conduit dropping down the house wall into the soil near the panel; a conduit stub, disconnect or subpanel on the garage or shed; irrigation heads, valve box lids and the controller (its valve wires often share the main lateral's trench); path lights and a transformer on an exterior receptacle; the propane regulator and where its line enters the house; the sewer cleanout and the vent stack on the roof (the building sewer leaves roughly below it); septic lids or risers; the pool equipment pad. The bonding ring is invisible by design. Sunken strips of lawn, grass that greens differently and patched concrete are trench scars worth noting.
What breaks if skipped: you only know a line exists, not where it goes, and you guess the route as a straight line it rarely follows.
3. Find the equipment at both ends and draw the line between them
Do it because a line you have found at one end only has an infinite number of possible routes. With both ends fixed, the likely route narrows to a corridor you can mark.
Pair each source with its load: panel to garage subpanel, controller to valve box, transformer to the farthest light, propane tank to the house entry, cleanout to tank inlet, pool pad to the panel and the pool wall. Mark a corridor, not a line, because installers bend around trees and old trenches. About 3 ft either side of the straight line is a planning assumption and nothing more.
What breaks if skipped: a line known at one end becomes "probably over there".
4. Know the depths you might find, and do not trust them
Do it because depth decides whether your work can reach a line at all, and shallow private lines are where most strikes happen.
NEC Table 300.5, as adopted by your jurisdiction, lets some private circuits sit surprisingly shallow: a residential 120 V branch circuit of 20 A or less with GFCI protection can be 12 in down, rigid metal conduit 6 in, and low-voltage landscape lighting limited to 30 V can be 6 in. Direct-buried UF cable without that GFCI condition is 24 in. Those are minimum covers, and homeowner-installed and older work is regularly shallower than the code allowed. Irrigation laterals are commonly within the top foot. The pool bonding ring under NEC 680.26, where a copper ring is used, runs 18 to 24 in out from the inside pool wall and only 4 to 6 in below the subgrade (the soil the deck paving sits on), which puts it exactly where a paver or fence crew works. A building sewer starts at whatever depth it leaves the foundation and gets deeper as it slopes toward the tank.
What breaks if skipped: a crew reasons "it must be deeper than my post hole" and is wrong by the full depth of the hole.
5. Hire a private locator when the ends do not settle the route
Do it because some lines cannot be found by looking, and a private locating service has the tools to find them.
Call one whenever a route crosses your work and you cannot fix it to within your hand-dig zone, and always for a feeder, a gas or propane line, or a sewer in the path of an auger. They clamp a signal onto a metallic line or tracer wire, use ground-penetrating radar for plastic pipe, and push a sonde (a small transmitter) down a sewer cleanout. Hand them your list from step 1.
On gas: federal pipeline rules at 49 CFR 192.16 require gas operators to tell customers that the operator does not maintain customer-owned buried piping past the meter, which is why a yard line to a pool heater or grill is the homeowner's to locate. On propane: some suppliers locate their own lines, and some states route propane through 811; ask the supplier directly.
What breaks if skipped: you rely on clues for the one line where a wrong guess is a fire or an electrocution.
6. Hand-dig inside the corridor and mark what you find
Do it because even a good locate is accurate to a zone, not a point.
Most state one-call laws set a tolerance zone around a public mark, commonly 18 in either side and wider in some states, inside which you expose the line by hand or vacuum before power equipment. Treat your private corridors the same way: expose, flag in a color your crew reserves for "private, found by us", and photograph with a tape in the frame.
What breaks if skipped: the private corridor becomes a suggestion, and the auger finds the line before the shovel does.
7. Write it down where the next crew will see it
Do it because you will be back, and so will other trades. Put each line, how it was found, its exposed depth and its corridor on a sketch in the job record.
A worked example: 19 fence posts and three crossings
A fence crew is setting a 140 ft run along the back and side property line, posts at 8 ft centers. 140 ft divided by 8 ft is 17.5 spans, rounded up to 18 spans, which takes 19 posts. Holes are 10 in across and 30 in deep.
The 811 locate marked gas and power to the meters on the front of the house. Nothing in the back yard.
Step 1, ask. The homeowner says the detached garage has power and the irrigation covers the back lawn. Asked about lights, they remember path lights along the side walk. Asked about propane, sewer and a pool: city sewer, no propane, no pool.
Step 2, clues. Gray conduit drops down the house wall below the panel, a subpanel sits on the garage's rear wall, the irrigation controller is on the garage, valve box lids sit 10 ft in from the back corner, and a lighting transformer is plugged in on the side of the house.
Step 3, both ends. Number the posts 1 to 19 from the back corner, so post 1 sits at 0 ft and post n at 8 times (n minus 1) ft: post 6 at 40 ft, post 7 at 48 ft, post 17 at 128 ft. The garage feeder runs panel to garage subpanel, and the straight line between them crosses the fence run 46 ft from the corner, between posts 6 and 7. The path lights run from the transformer along the side walk to the back gate, crossing the fence run at the gate near post 17 (128 ft). The irrigation main runs from the house hose bib to the valve boxes, which sit inside the fence line and never cross it, but one lateral feeds heads outside the fence along the alley.
Step 4, depths. The feeder is in conduit from the wall, so it could be as shallow as 6 in if it is rigid metal, 18 in if PVC. The lighting cable could be at 6 in or less. The laterals are within a foot. Every one is shallower than a 30 in post hole.
Step 5, private locator. The feeder is a power line in the path of an auger, so the shop calls a private locator, who clamps onto the feeder at the subpanel and marks it crossing the fence line at 43 ft. That is 43 minus 40, 3 ft from post 6, and 48 minus 43, 5 ft from post 7: outside the 10 in hole of each, inside the corridor the crew assumed, and 46 minus 43, 3 ft from where the straight line put it. The locator also traces the lighting cable to 1 ft from the gate post.
Step 6, hand-dig. The crew hand-digs posts 6 and 7, finds the feeder conduit at 19 in at the crossing, gray PVC. They shift the gate post 8 in toward the house to clear the lighting cable, and hand-dig the two posts either side of the lateral, finding it at 7 in and clearing it.
Result. All 19 posts set, three private crossings found, two by the locator and one by hand, nothing struck. The straight-line guess from step 3 was 3 ft off on the feeder, which is why the shop paid for the locate rather than trusting the line.
What would change the call
- A pool in the yard: the bonding ring sits a few inches down under the deck, 18 to 24 in out from the pool wall, so any post or footing within about 3 ft of the pool wall is hand-dug, and the pool feeder gets the same private locate as the garage feeder.
- Septic instead of sewer: the building sewer, tank and field all get located before any hole, and the field gets no posts, footings or vehicle traffic at all. See related: Septic Fields for Landscapers, Fence and Deck Builders.
- No end found for a line you know exists (the homeowner says there is power to the shed and you cannot see the feed): that is the case for the private locator, not for more guessing.
How to know you got it right
Before the first hole, every line from step 1 has a corridor or an exposed point on the sketch, or a note saying why not, and every crossing of your work area has a hand-dig flag.
References
- NFPA 70 (NEC), Table 300.5 and Section 680.26, as adopted by your jurisdiction
- 49 CFR 192.16, customer notification of customer-owned buried piping
- Your state's one-call (811) law for the tolerance zone and hand-dig requirement
- See related: The Utility Locate: Before You Dig
- See related: Irrigation Systems for the Outdoor Trades That Dig Around Them, Pool and Spa Electrical Bonding Reference