Repiping & Whole-Home Pipe Replacement
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Plain-English article
PEX vs Copper Pipe in Thornton, CO: Which Is Better?
If you are planning a repipe or a remodel, the plumber will ask which pipe you prefer. Both are approved, and each has strengths. The right choice depends on your house, your water and your budget.
By the Thornton Plumbing Co. team ·
What PEX is
PEX is cross-linked polyethylene, a flexible plastic pipe that comes in coils and in red, blue and white colors. It bends around corners, so it needs fewer fittings, and it can be run from a central manifold to each fixture.
It is quick to install and resists corrosion and scale. It is not suitable for outdoor exposure to sunlight, so it must be covered.
What copper is
Copper is a metal pipe with a long record. It is rigid, joins with soldered or pressed fittings and resists heat. It has served houses for generations.
Copper can corrode in some water chemistries and develop pinhole leaks. Hard water scale builds inside it, but the metal itself usually lasts a long time.
Freezing
Water expands when it freezes, and a frozen pipe can split. PEX is more forgiving, because it can expand slightly and frequently makes it through a freeze that would burst copper. It is not freeze proof, and a pipe left to freeze repeatedly will fail.
Insulation matters for both. Wrap pipes in unheated spaces, and keep cabinet doors open on cold nights.
Cost and labor
PEX material is often less expensive, and installation is faster. Copper costs more in material and labor. For a whole-house repipe, that difference can be large.
Ask the plumber for a written scope with both options so you can compare.
PEX and copper side by side
A quick comparison of the main points.
| Feature | PEX | Copper |
|---|---|---|
| Installation | Flexible, fast, fewer fittings | Rigid, more fittings and labor |
| Freeze tolerance | Better, though not freeze proof | Splits more easily |
| Scale and corrosion | Resists both | Can pit in some water |
| Outdoor exposure | Needs protection from sun | Handles exposure |
Water quality and taste
Both pipes are approved for drinking water. New PEX can give water a faint plastic taste at first, which fades after the lines are flushed. Copper can add a metallic taste in some water.
Thornton's water is hard, with an average near 13.5 grains per gallon. Scale does not clog PEX the same way it narrows older steel, and copper tolerates it well.
Which to choose
For a whole-house repipe, PEX is common because of speed and cost. For exposed runs, a remodel with visible pipe or a preference for metal, copper is a good choice.
Talk to your plumber about permits, warranties and layout. See repiping for the process.
How the two materials differ in the wall
Copper is rigid metal tubing, joined with soldered fittings or pressed fittings. It handles heat well, resists sunlight, and has been used in houses for generations. PEX is a flexible cross-linked polyethylene tube that bends around corners, which means fewer fittings and a faster install. It is joined by crimp rings, expansion rings or push-fit connectors, depending on the system.
Neither is better in every situation. The right choice depends on the job, the house, the water and the budget, and the answer for a short repair differs from the answer for a full repipe.
Water chemistry and what it does to pipe
Thornton's 2025 water quality report lists an average hardness near 230 mg/L, about 13.5 grains per gallon, and an average pH around 8.1. Hard water leaves scale on hot surfaces, and that matters more for a water heater and its fittings than for the pipe wall itself. A chloraminated supply, which the city uses, is gentler on some materials and harsher on others, notably rubber parts. Plumbers often recommend fittings and seals rated for chloramine.
Copper with pinhole leaks is usually a sign of local corrosion from something in the water or the installation, not of age alone, so a repair on one pinhole can be followed by more. That is the main reason a house with repeated copper pinholes gets a repipe quote. See repiping and whole-home pipe replacement for what that involves.
Freezing, noise and installation
PEX tolerates a freeze better than rigid pipe because it stretches before it splits, but it is not freeze proof, and the fittings can still crack. Copper is the less forgiving of the two in a hard freeze. Both need insulation in unheated spaces, and PEX should never sit in direct sunlight, since ultraviolet light degrades it. Keep it covered before it gets to the exterior of the house.
PEX runs tend to be quieter, because the tube flexes a little and does not carry water hammer as loudly as hard pipe. Copper can ring if it is not strapped properly. Both can be loud if the pressure is too high.
Questions to ask before a repipe
Ask which material the contractor proposes and why, which fitting type they use, and whether the quote includes the drywall patching, permits and inspection. Find out what happens to the old pipe, how many hours each day the water is off and what warranty covers the work, and get all of it in writing.
Remember that the contractor sets the price and the terms, not this website. Compare two or three written quotes that describe the same scope, and check the license status of whoever signs it through the state.
A note on mixing materials
It is common to join PEX to existing copper during a partial repair. Use fittings made for the transition, and check that dissimilar metals are not touching in a way that corrodes. Ask your plumber to note the materials on the invoice so the next person who opens the wall knows what to expect.
Cost, permits and resale
Material cost is only part of a quote, since labor, drywall repair and permits also count. Some buyers and insurers have views on certain pipe types, so ask your agent or insurer if it matters to you.
Quick answers
Asked about PEX and copper
Yes, approved PEX is safe. Flush new lines before use.
Each can last for decades. Water quality and installation matter.
It can, but it tolerates freezing better than copper.
Yes, using fittings approved for the transition.
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Related reading
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How to thaw frozen pipes
A frozen pipe is a warning, not yet a flood. Here is how to thaw one safely, when to stop and what to do if it splits. Open page
Planning a repipe?
Call with the age of the house and the pipe type you have seen.