I recently had a Slab leak in my home in Indianapolis,IN. This is the 4th Slab leak since I've owned the home. I decided it was time to reroute all the Water lines. I thought this was best so I wouldn't have to deal with anymore slab issues. We had pex lines run through our attic space to the bathrooms and laundry area. Pex had to be ran under the concrete from the utility closet to the Kitchen. All the lines are tied to a Manifold. After reading some info on this site, I am alarmed that we may have frozen lines in the cold temp. The pex was run about 3 maybe 4 feet above the blown in insulation. The lines were fastened to the rafters. Black insulation was used to wrap the lines. I've been told that this is out of code in Indiana and that the lines need to be rerun inside the home. Just below celing. Then celing would have to be framed and new drywall attached. Help! Anyone that can provide any information about what we should do, would be appreciated.

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    Well, bottom line is that the lines do need to be routed so that they are in warm space. Who was it that decided to mount the lines above the attic insulation? (A contractor from southern California where attic water line installs are common?) Maybe the proper fix for the under the slab routing of the water lines was to install 4" diameter PVC piping under/through the slab that has all gradual turn corners. Through this can be pulled the PEX water lines. If ever a leak you can pull new lines through the PVC without digging up slab once again.
    – Michael Karas
    Commented Nov 15, 2013 at 11:16
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    My money says the lines will freeze. PEX is pretty resilient to splitting when water freezes inside it, however the fittings are not. This is a leak waiting to happen. Also, I can't imagine a licensed/bonded plumber did the work; that could impact insurance coverage if a leak results in damage. Commented Nov 15, 2013 at 12:52
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    Possible duplicate: Will a PEX run freeze if it's in the attic above a foyer?
    – BMitch
    Commented Nov 15, 2013 at 14:01
  • There are no joints in THE PEX in attic.
    – user18116
    Commented Nov 15, 2013 at 16:38
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    @user18116 I think you still run a high risk of your pipes freezing. If there are no tee's or joints in the cold area, it seems less likely to me that you would have a leak. Commented Nov 16, 2013 at 2:25

6 Answers 6


The simple solution is to dig up the insulation, run the pipes along the top of the ceiling drywall (ie, just above the ceiling, rather than just below it), and put the insulation back on top of them, which puts them on the warm side of the insulation, "inside the home (thermally speaking)." Also to be a lot more careful when hiring "plumbers."

Otherwise, framing in a pipe chase below the ceiling would work, and might actually be easier in some cases (where crossing rather than running along ceiling joists.)

  • I agree pex is easy to move arround pull it down a bury in the insulation. Since you don't have any fittings in the attic I doubt you will have any problems with the pex buried in insulation.+
    – Ed Beal
    Commented Nov 23, 2018 at 18:52
  • Time to install that crown molding that I've always wanted.
    – popham
    Commented Oct 12, 2023 at 20:16

Well I am a master plumber in Indiana for 33 years. If you think putting water lines in an attic is a good idea, then enjoy that massive insurance claim. It is against code. To make it legal you would have to stack the insulation damn near to the roof. You can not close all your ventilation to your arrive. That causes condensation which causes mold. Indiana winters can be harsh. Is it worth the risk? The only thing that is more damaging to a house , other than fire , is water. Keep that in mind and good luck


I had to replumb my house to get rid of the crappy poly-B piping that has been vexing me with leaks for the past two decades. Rather than rip out my interior to put new PEX pipes in, I ran two 3/4 inch PEX risers up inside my chimney chase from the basement all the way to the attic. From there, I located the top wall plates and dropped half-inch lines off the 3/4 down into the walls for the bathrooms. I made small cuts in the back of the vanity cabinets and brought the new pipes into view. For bathtubs, I was able to cut small access holes in closet walls opposite the tubs. I fit nice little flush-mount panels back in to fill the holes.

My attic had 12 inches of blown rockwool insulation. I dug little trenches down to the ceiling drywall so I could lay the pipes right in the drywall. I made little U-channel box covers out of styrofoam to cover the pipes, and then filled the rockwool on top. This created a little cavity where heat from the house can dissipate (through the drywall) so the pipes stay essentially at house temperature. Also, for added insurance, I laid a heat-tracer tape (made for that purpose) alongside the pipes. It is thermostatically controlled and will come on as the temp drops below 40F. Given the location of the pipes (right on the drywall) and the insulating method I used, I doubt the tape will ever come on. I also put a remote reading thermometer up there at a point right on the pipes so I can monitor the temperature at that point remotely. Knowing I'd have to do this plumbing retrofit, I put the thermometer up there last fall, and it remained within a degree of room temperature all winter, even in February when it exceeded -30 for some time.

If done carefully, you can avoid any potential for freezing, but proper location and insulation is the key. The heat-tracer tape is 80 feet long, cost $120, and gives off about 3 watts per foot. It just gets pleasantly warm, but not hot.


I don't see where running your line under the ceiling insulation yes you should try to keep the fitting in the walls but also heat rises and if you insulate the lines i really don't see it freezes. Also if you feel its going the be real cold at times you can alway let the water run at trickle to stop from freezing.

  • It gets really cold in that location I have seen -20 and below so putting the apex under the insulation would be a good idea.
    – Ed Beal
    Commented Nov 23, 2018 at 18:55

This advice is coming from a Master Electrical Engineer who graduated from Penn State in 2012, so take the advice with a grain of salt.

First off, these days water lines going through Attic are standard practice especially if you have a slab concrete foundation. The makes the price affordable and allows for minimum tear down during the plumbing repair. While this will may make you work a little more to properly insulate the water lines, it will save you tons of money upfront.

Installation technique for PEX lines in the Attic varies according to geographic location. For example, Montana that has those average winter cold nights of -7°C (Wikipedia) will need some extra insulation on PEX lines to account for those windy nights where the chill factor and any non-desired holes allowing airflow to drop the temperature in the Attic further. Remember that Attic temperatures need ventilation holes be it gable grill, soffit ports, turbines, or any Attic fan in order to match Attic temperature to outside temperature and also to control humidity and condensation in the Attic.

Having analyzed that Attic temperatures should be 10 to 15 degrees warmer with adequate ventilation, it is my opinion that sufficient insulation around PEX tubing should keep the lines from freezing. Do use the sticky tape to create a hermetic enclosure for the new PEX water lines. If they freeze for any reason, check your Attic ventilation and seal ventilation holes during the winter to warm the Attic. You can also consider using an Attic heater if one exists in order to keep the temperature just above 0°C.

  • 2
    Daniel, you won't graduate for 84 more years? Commented Nov 23, 2018 at 18:49

In Indianapolis you're under an amended version of the 2006 International Plumbing Code. From the list of amendments:

Delete the text of Section 305.6.1 and insert to read as follows: Waterlines. Waterlines shall not be installed outside of a building, in attics or crawlspaces, or in any other place subjected to freezing temperatures, unless adequate provision is made to protect such waterlines from freezing by insulation, ambient heat, or alternate heat source. No waterlines shall be concealed in outside walls, above grade.

There's actually a mistake in this amendment, where it should be referencing 305.6, not 305.6.1. Regardless, your waterlines don't need to be below the ceiling. They just need "adequate provision" to protect from freezing, and they can't be located in exterior walls. Google puts Indiana's frost line between 24" and 36", where the length of waterline involved in your system needs to be itself heated (depending on the length, this could be a cheap solution until you can afford a more permanent solution) or it needs to be located within your home's thermal envelope.

For locating inside your home's thermal envelope, the waterline should be run beside ceiling joists and through ceiling joists. For lines running parallel to the joists, attach the waterline to the ceiling joists every 2'-8" or less. For lines running perpendicular to the ceiling joists, bore holes in the ceiling joists where the hole edge doesn't come within 1-1/2" of the ceiling's drywall. Maybe you could get away with strapping the water lines to the tops of ceiling joists, but I would be afraid of an inspector rejecting this as a "location exposed to damage." I would reject it if I was an inspector.

The 1-1/2" comes from the 2006 IPC's 305.8:

In concealed locations where piping, other than cast-iron or galvanized steel, is installed through holes or notches in studs, joists, rafters or similar members less than 1.5 inches (38 mm) from the nearest edge of the member, the pipe shall be protected by shield plates. Protective shield plates shall be a minimum of 0.062-inch-thick (1.6 mm) steel, shall cover the area of the pipe where the member is notched or bored, and shall extend a minimum of 2 inches (51 mm) above sole plates and below top plates.

The 2'-8" spacing along ceiling joists comes from Table 308.5 which specifies a maximum hanger spacing of 2.67 feet for horizontal PEX runs and 10 feet for vertical PEX runs.

Any pipe laying on the face of your ceiling's drywall is not conformant.

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