If copper is spraying or dripping steadily, shut off the main water valve first. Then open a faucet at the lowest level to drain the lines, and keep clear of wet outlets and cords. We answer the line 24/7, and a leak that cannot be shut off is a same-day job when available.
A slow weep is different. It lets you gather the facts: which pipe, hot or cold, how old, and whether the spot is at a joint or in the middle of a run. This guide walks through those questions, what each fix really does, and where honest limits lie.
Shut it off first, then size up the leak
Do these in order. None of them needs a tool beyond what most basements already have.
- Close the main valve.Turn the house main clockwise until it stops. If it will not close or leaks at the stem, stop and call. Do not force a seized valve.
- Drain the lines.Open the lowest faucet and one upstairs. Pressure drops and the leak slows. This also keeps the pipe dry enough to look at.
- Protect what is below.Catch drips, lift stored items off the floor and keep water away from outlets, cords and the electrical panel.
- Look before you touch.Note whether the leak is at a joint, in the middle of a pipe or at a valve. Take a photo. Green crust, a wet pin-sized spot or a bulge tells us a lot.
The city maintains the water mains, and it says it can shut off service when a plumber advises it is necessary. If your house valve will not close, tell us and we can advise on that.
Pinhole leaks versus joint leaks
The location of the leak points to the cause. Sort yours into one of these before choosing a fix.
Pinhole in the pipe wall.
A tiny spray or a wet bead in the middle of a straight run. The wall has thinned from the inside. Where there is one, others are often forming.
Weeping solder joint.
A damp, crusty ring where two pieces meet. This can come from a joint that was never fully filled, or from slow corrosion at the joint.
Leaking fitting or valve.
Drips at a compression nut, a packing nut or a union. These often respond to tightening or a new washer, not a pipe repair.
Freeze split.
A lengthwise slit in the pipe, usually on an exterior wall or an unheated space. It is a burst pipe, so shut off the water and treat it as urgent.
Why copper develops pinholes
Copper does not usually fail from age alone. It fails when something in or around the pipe keeps wearing at one spot. Water chemistry is the first suspect, because water that is aggressive toward copper can pit the inside wall over years.
Flux is a quieter cause. Acid flux used when joints were soldered can leave residue inside the pipe. That residue can eat at the wall near the joint, and the leak shows up long after the installer is gone.
Fast hot water is the third. Water moving quickly through a hot line, or through a pipe with sharp bends and burrs, can scour a thin spot in the wall. Old, thin-walled pipe fails sooner under the same conditions. We cannot always name one cause from a single leak, and we will say so when that is the case.
Cutting out a leaking copper section and joining new pipe is plumbing work under the Minnesota Plumbing Code (Rules chapter 4714). A push-fit coupling is a common stopgap, but check the manufacturer's rating before you bury one inside a wall.
What the Rosemount water report says about copper
The city lists its water hardness as 17 grains per gallon, which it calls hard. Hard water leaves scale, and many homes run a softener to deal with it. The city's own 2025 water report lists benefits of softening, including less scale in pipes and fixtures, and also lists a disadvantage: it says softened water can corrode your pipes.
That is a trade-off, not a verdict on softeners. If you have pinholes and a softener, have the softener serviced and ask us to look at the pipe, since the two can be linked. The same report says the city treats its water to prevent corrosion of lead and copper, so the water leaving the plant is managed for it.
On the property side, the city says homeowners are responsible for the service line and all plumbing on site. A leak inside your walls is yours to fix. For water quality questions, the city's Public Works office is the right place to call.
Source: City of Rosemount 2025 Drinking Water Report (rosemountmn.gov), City of Rosemount Water page and Public Works FAQ, City of Rosemount Service Line Inventory page.
Copper leaking now?
Call us. We can talk you through the shutoff, then give a clear price before work starts on the repair.
Temporary fix or lasting repair
Every option below stops water. They differ in how long they hold and what they leave behind.
| Fix | Treat it as | Good for | Limits |
|---|---|---|---|
| Repair clamp or sleeve. | Temporary. | Stopping a pinhole until a plumber can cut it out. | Does not fix the thinning pipe around it. |
| Epoxy putty or wrap tape. | Emergency only. | Slowing a drip for a short time. | Fails under pressure and heat. Never a repair. |
| Push-fit coupling. | Often lasting. | Replacing a cut-out section quickly, even on a pipe that is hard to dry. | Needs clean, round, deburred pipe. Hidden fittings still need access. |
| Soldered or pressed coupling. | Lasting. | Replacing a damaged section with a proper joint. | Needs a dry pipe and room to work. |
| Repiping the run. | Lasting. | A line with repeated pinholes. | Opens walls and costs more up front. |
A clamp that has been on for months is a decision you postponed. Put a date on replacing it.
Signs that repeated leaks mean it is time to repipe
One leak is a repair. A pattern is a diagnosis. These signs say the pipe itself has become the problem.
- A second pinhole within a short time.Same line, different spot. Each repair buys less time than the last.
- Blue-green stains on several pipes.Crusty corrosion on more than one run points to a system-wide issue, not a one-off.
- Thin, pitted wall when cut.When we cut a section out, the inside tells the story. A wall that looks scraped or honeycombed is near the end.
- Leaks in different rooms.If hot and cold lines both leak in separate parts of the house, patching section by section costs more over time.
- Discolored water or falling pressure.Corrosion inside the pipe can show up at the tap before it shows up in the wall.
If your pattern fits, read our repiping page for what a replacement involves. If you are not sure whether the pipe is the issue or a hidden leak is, our leak detection service can find the source before anything is opened.
What a lasting repair visit looks like
We shut off and drain the line, then cut out the damaged section with a tubing cutter instead of a saw. The new piece goes in with a proper joint, and we check the pipe on either side for more thinning. Then the line is repressurized and watched for weeping.
We also look for the cause. That means the age of the pipe, the softener setting, the water heater connections and any recirculation line. You get a clear price before work starts, and we tell you if the honest answer is that this run is nearing the end.
If you live in a nearby town
Chemistry nearby looks similar. Farmington's city pages put its water around 16 grains per gallon, and the city lists the same softening pros and cons that Rosemount does. Hastings reports 16 grains per gallon and calls it moderately hard. If you are in Farmington or Hastings, the same copper questions apply.
Permits are a local question. The city of Hastings lists plumbing permits for repaired or altered systems, including water line replacement. For a bigger repipe in Rosemount, call the city Building Permits and Inspections office at 651-322-2024 and ask what applies before work starts. We will not guess at a rule that the city has not published.
Copper leak questions
You can slow it with a clamp or sleeve rated for the pipe, and many homeowners do. It is a stopgap. The wall around the pinhole is thin, so plan to have that section cut out and replaced.
Good ones are made for permanent use when the pipe is cut square, cleaned and deburred, and pushed to the depth mark. They fail when the pipe is rough, out of round or not fully seated.
We cannot say that from one leak. The city lists its water as 17 grains per gallon and says it treats the water to prevent corrosion of lead and copper. Its own report also says softening can corrode pipes. Have the pipe and any softener checked, and ask the city's Public Works office about water quality.
There is no fixed count. A second pinhole in the same line within a short time is a strong signal. So are stains on several pipes and a pipe that looks scraped inside when cut.
Yes, pinholes often spray into a wall cavity and show up as a stain much later. If you see a stain, shut off the water and call. Leak detection can find the source without opening a whole wall.
Yes. The line is answered 24/7. Shut off the main first, drain the lines and call. Same-day appointments are available when schedules allow.