Small galvanized pipes sticking out of the ground are usually old irrigation risers, hose bib or sprinkler stubs, capped water lines, cleanouts, or well vents. Some are gas stubs, and elsewhere, oil tank pipes. Don't cut, cap, or dig near one until you know which it is.
What are the pipes most likely to be?
These are possibilities to investigate; the table is not a way to rule out a live gas or water line.
| What it might be | What it looks like | Usual clue |
|---|---|---|
| Flood irrigation standpipe or riser | Pipe or concrete box with a gate or valve, often near a lot wall or fence line | Older SRP-area neighborhoods |
| Old hose bib or sprinkler riser | Short pipe with a threaded top or a leftover faucet body | Sits along the house or a planting bed |
| Capped water stub | Threaded pipe end with a cap or plug | Left from a removed line, pool, or addition |
| Gas stub | Steel pipe with a cap or valve, running toward the house, meter, or an outdoor appliance spot | Can be live. Treat unknowns as gas |
| Sewer cleanout | Larger capped pipe or fitting at ground level | Near the foundation or property line |
| Well or septic vent | Pipe near an old pump house, well, or septic tank | Not the same as a roof vent |
| Oil tank fill and vent pair | Two pipes a couple of feet apart, one may have a flap, one a mushroom-shaped cap | Rare in Phoenix, common in older homes elsewhere |
| Clothesline post, fence post, or conduit | Solid or open-topped pole, or pipe with wires | Not plumbing at all |
### Old irrigation risers and standpipes
In older parts of the Valley, the most likely answer is the neighborhood's flood irrigation system. SRP's owner's manual says private irrigation systems are "not owned, operated or maintained by SRP" and are made up of "ditches, pipelines, standpipes, berms and valves." It defines a standbox or standpipe as "Structures containing gates and valves that divert water into a private irrigation system." If your lot has a valve or gate near a wall, that's a strong clue.
Those pipes can matter to your neighbors, since a flood irrigation system can be shared by several lots. Don't remove or cut one without checking with SRP or your irrigation neighbors. Our page comparing SRP and city water explains who does what.
Sprinkler risers are a cousin. An old galvanized riser feeds a sprinkler head or a valve. If it's broken or leaking, see our pages on fixing drip irrigation and sprinkler backflow devices.
### Hose bibs, water stubs, and capped lines
A pipe with a threaded end is often an old water line that fed a hose bib, a pool fill, a garage sink, or a laundry that has since been changed. Our page on leaking hose bibs covers the working ones, and the one on vacuum breakers covers what should be on the faucet.
Here's the catch: a capped stub may still be pressurized, and galvanized pipe that's decades old can break at the threads when you turn it. Our page on problems with galvanized pipe explains why it fails. If the line is live, the fix is to shut it off at the source and cap it properly, not twist the cap off to find out.
### Gas stubs
Some stubs are old gas lines to a grill, a pool heater, a patio heater, or a detached building. They may end in a valve or a cap, and they can still hold gas. If a stub runs toward the gas meter, or toward where an appliance once sat, treat it as gas until a licensed plumber proves otherwise.
Southwest Gas says a leak can show up as a rotten-egg smell, "a hissing or roaring sound near the ground," or "blowing dirt, bubbling water, or dead or discolored vegetation near a pipeline or meter." Any of those near a stub means leave and call.
Another point most people miss: An 811 request does not establish that every private line on your property has been marked. Buried gas on your side of the meter, plus private water, irrigation, and sewer lines, may not be marked at all. That's a good reason to identify a stub before you dig anywhere near it. For related work, see our pages on gas lines to a grill, gas lines for pool heaters, and turning off the gas to your house.
### Cleanouts, vents, wells, and septic pipes
A larger capped fitting near the foundation is likely a sewer cleanout. A short pipe by a septic tank may be a vent or riser. Neither should be cut or cemented over. See our pages on sewer cleanouts, plumbing vents, and septic versus city sewer.
Old wells deserve extra caution. The Arizona Department of Water Resources runs a program to "identify open wells, notify the well owners, and ensure that these hazards are properly capped or abandoned." If a pipe sits in or over a hole, or you can hear or see a void, keep kids and pets away and call ADWR. Our page on home well systems in Arizona covers working wells.
### Oil tank fill and vent pipes
This one is rare in Phoenix and much more common in older homes elsewhere, but buyers relocating from those areas ask about it. Two pipes a couple of feet apart, one sometimes with a hinged flap and the other with a mushroom-shaped cap, are typically the fill and vent of an old heating oil tank. The EPA says heating oil tanks used on the premises are excluded from federal underground tank rules, but "state or local regulatory agencies may regulate these tanks." Michigan's environmental agency advises removing a fill pipe or locking it closed "to prevent a mistaken delivery." Ask your local building or environmental office what applies.
How can you check safely?
You can identify most stubs without touching them, using the steps below.
- 1Look, don't dig. Photograph the pipe, note its diameter and top, and see where it points.
- 2Trace it. Does it head toward the house, a meter, a wall, a pool, or a septic lid?
- 3Check records. Old permits, the plans you got at purchase, or neighbors in the same subdivision can identify the stub fast. Our page on finding where water pipes run has other ways to trace lines.
- 4Call before any digging. Arizona law requires the underground-facility notice process before excavation, with at least two working days' notice under A.R.S. 40-360.22. Wait for the required responses and markings. Call 811 or use arizona811.com. Remember it won't mark your private lines, so it doesn't make a stub safe to dig around.
- 5Don't do these: cut it, unscrew a cap, pour concrete on it, or dig around it. Water pipes can spray, gas can leak, and old wells can be unstable.
When should you have a plumber look?
Have a licensed plumber look whenever a stub is live, unknown, or in the way of a project.
Call one if the pipe is wet, warm, hissing, or leaking; if it lines up with the gas meter; if you can't tell what it is; or if you plan any work near it. Older Phoenix homes hide plenty, and our page on common plumbing problems in older Phoenix homes and the guide to signs of old, failing pipes show what else to watch for.
HQ Plumbing & Air is licensed and insured, and offers free estimates and 24/7 emergency service. We can identify the stub, tell you what's live, and cap or remove it the right way.