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Install PEX Water Lines — Run the Hot and Cold Water Supply Lines

Intermediate

Part of project

How to Rough-In Plumbing for a Bathroom Vanity · Step 5 of 8

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In this video

The presenter prepares for and installs the PEX water supply lines. Using a drill with a 5/8-inch auger bit, he drills two holes through the wooden bottom plate of the wall, one for the hot and one for the cold line, aligning them below the corresponding inlets on the outlet box. He feeds the red and blue PEX pipes up through the holes. For each line, he slides a 1/2-inch stainless steel crimp ring onto the pipe. He then pushes the end of the PEX pipe fully onto the brass barb fitting of the valve. He positions the crimp ring about 1/8 of an inch from the base of the fitting. Using a PEX crimping tool, he squeezes the handles until the tool fully closes, which compresses the ring and secures the pipe to the fitting, creating a permanent, leak-proof connection. He repeats the process for the second water line.

Goal: Connect the hot and cold PEX water lines to the outlet box valves

  • Ensure the PEX pipe is fully seated on the barb fitting before crimping the ring.
  • Position the crimp ring 1/8 to 1/4 inch from the end of the pipe to allow for proper compression without damaging the fitting.

Used in this video

  • Cordless Drill (brand: Ridgid, Tool Type: Power Tools, Power Source: Battery) — Drilling holes for the PEX pipes.
  • Auger Drill Bit (brand: Unbranded, Material: Metal, Size/Dimensions: 5/8 inch) — Drilling clean holes in the wood frame.
  • PEX Crimping Tool (brand: Unbranded, Tool Type: Hand Tools, Power Source: Manual) — Securing crimp rings onto PEX pipes and fittings.
  • Pliers (brand: Unbranded, Tool Type: Hand Tools, Power Source: Manual) · optional — Temporarily holding the crimp ring in place before using the crimping tool.
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FAQs

How difficult is it to rough-in plumbing for a vanity, and how long should I expect it to take?

This project is rated "intermediate" because it requires precise measurements, proper pipe joining techniques, and an understanding of plumbing codes. For a DIYer with some experience, expect 8-16 hours of work, depending on existing wall access and any unforeseen issues. Costs can range from $150-$300 for materials, assuming you already own basic tools.

What are the most crucial safety precautions I should take when roughing-in plumbing?

Always shut off the main water supply before cutting into existing lines to prevent flooding. Wear appropriate personal protective equipment (PPE) like safety glasses, gloves, and hearing protection, especially when using power tools like drills and hole saws. Be mindful of electrical wires inside walls when drilling or cutting.

The guide mentions PEX for supply lines; can I use copper or CPVC instead, and what are the pros of PEX?

While copper and CPVC are alternatives, PEX is often preferred for DIY projects due to its flexibility, ease of installation (fewer fittings, no soldering), and resistance to freezing. However, PEX requires specific crimp or expansion tools. If you're comfortable with soldering, copper is a durable choice, and CPVC offers a rigid, solvent-weld option.

What are the most common mistakes DIYers make when roughing-in a vanity's drain and supply lines?

A common mistake is incorrect drain slope, leading to clogs – ensure a 1/4 inch per foot slope for DWV lines. Another error is misplacing supply stub-outs, making fixture installation difficult; always double-check vanity and sink specifications. Also, failing to properly prime and cement PVC joints can cause leaks.

Transcript
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And now that we're secure we need to work on installing these pressure lines. Let's get to it. Now you need to get a five eight since drill bit and a drill to accommodate half inch pipe because we're going to have to put the pipe down through the floor in this case. So what you need to do to transcribe the marks is measure off your stud looks like we've got six inches and eight and three eights. So we need transcribe that off the stud on the floor to go down below. So we're going to measure over six inches and eight and three eights. We're going to make a mark. All right. And as you notice from above and this drain is kind of back towards inside this wall we got to keep our pressure lines out towards the front of this plate. So we're going to go back just about three quarters of an inch here. Now it's time to install our pecs. This is pecs type B and this is going to get crimper rings on it and we're going to use the red color for the hot side and the blue color for the red side. So all we got to do is get our half inch crimper rings. Slide them over the pipe first just like that. And now we just slide it up over the fitting like so. And we try to stay about eight inch down from the end of that fitting. And now what I like to do I just take a pair of pliers and just crimp it on enough to hold into place just so it doesn't slide around. Then I take my crimping tool and then it's going to crimp that ring on there tight and it's never going to come off unless you cut it off. Okay. And now we're going to do the same thing with our hot side. Slide it over. Get it about an eighth inch from the fitting. And like I said, I like to use my needle nose to crimp it on temporarily and then we're going to go ahead and get that one fastened. Boom. So now we got a fitting that is never going to have a leak unless improperly installed.

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