Cpvc & Pvc

I understand that CPVC pipe is acceptable for interior plumbing but PVC pipe is not because PVC pipe is not as strong as CVPC.

What about the fittings? I know they make CPVC fittings and have no idea why somebody didn’t use them here.

Heres the pic, any comments, please?


From my understanding the two are not compatible. They will not glue to each other properly. The connections will leek.

At one time I thought that one was OK for cold water only & the other was OK for both cold & hot water lines.

I have never heard that PVC was not acceptable for water supply. I would never use PVC or CPVC outdoors myself though.

CPVC & PVC are like copper & Galvanized pipe, they should not be connected directly to each other.

If anything is not correct please let me know & point out why I am not correct. Thanks.

PVC is not allowed for interior distribution. That is to say, no PVC piping, and no PVC fittings.

Regardless of their compatibility, PVC is not allowed.

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Pvc is for cold water and o.k. and cpvc is for hot water and is o.k., they are not compatible because of size differences. Pvc works fine outdoors buried, but does not handle uv rays well at all. It will get real brittle. They do require different glues.

PVC is used all the time for outside (i.e. sprinkler systems.)

PVC is allowed for exterior use as service or cold water distribution - whether irrigation or potable supply.

PVC (piping and/or fittings) is not allowed for use inside the residence.

Jeff, can you point out the reasoning behind PVC NOT OK for use indoors? I just do not understand why it would be OK for outdoor potable but not indoor potable supply? Outdoor is a much more harsh environment then indoor. I would think that if used outdoor it would have to be quite durable and if it can be used for potable outdoors then it must not have any chemicals that would be considered hazardous for human consumption.

I would just like to understand the reasoning behind this. Can a code be pointed out…

I do see the chart in the CODE CHECK, I would like to understand the reasons.

Prohibited Joints
–No glued joints between different types of plastic. IRC[2904.16.2] UPC{316.1.6}
–No female threaded PVC fittings. IRC[2904.16.2] UPC{606.2.2}

I’m not sure I can provide you with the **reasoning **(although I believe it has to do with the temperature rating), but I can provide you with the code sections.

CPC (UPC) 604.1 Water distribution pipe, building supply water pipe and fittings shall be of brass, copper, cast iron, galvanized malleable iron, galvanized wrought iron, galvanized steel, or other approved materials. Asbestos-cement, CPVC, PE, PVC, or PEX water pipe manufactured to recognized standards may be used for cold water distribution systems outside a building. CPVC, PEX water pipe, tubing, and fittings, manufactured to recognized standards may be used for hot and cold water distribution systems within a building. All materials used in the water supply system, except valves and similar devices shall be of a like material, except where otherwise approved by the Administrative Authority.

For the IRC, refer to Table T2904.5

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Thanks Jeff, That was the only thing I could think of myself.

Does anyone else have any other idea why PVC can not be used indoor for potable, cold water. I know it can not be used for hot water.

Also does anyone know if PVC was ever OK for potable water. We have this kind of discussions all the time about Electrical… why not about plumbing!

Code inspectors can not quickly determine if PVC is present for the hot lines so they just disallow it completely for all of the indoor lines.

This might help some.


Plastic pressure piping is used for many industrial processes, in heating and cooling systems, fire protection installations, gas distribution, and for water supply and distribution.

Potable water applications include cold water services from wells or water mains up to the building as well as hot and cold water distribution piping within buildings.
ABS, PE and PVC materials are all available with 73 F stress rating for use in pressure piping. PE piping is used extensively for cold water service lines and water distribution systems outside the building. Its low temperature flexibility make it especially suited for use in applications where temperature of 35 F and lower will occur.
The maximum temperature at which PE has an HDS rating is 140 F.

Chlorinated Poly (Vinyl Chloride) (CPVC), and cross-linked polyethylene (PEX) materials are available that are rated for long term service at 180 F as well as for cold water applications. Hot and cold water distribution system piping made from these materials has a working pressure rating of 100 psi at 180 F. These systems are tested at 150 psi at 210 F for at least 48 hours to assure integrity at those condition, which may develop in the event the water heater controls malfunction. Thus, such materials are suitable for hot water distribution where water heaters are installed with relief valves set at 150 psi, 210 F.
All plumbing codes require the use of piping having the 100 psi @ 180 F rating for both the hot and the cold water portions of the water distribution system.


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That makes a lot of sense.
We know it is sanitary because it is allowed for main service pipe.
Ive been using SCH 40 PVC for years as air piping in cabinet shops and we often run 140 psi., so it can handle the pressure.

Marcel is right. It has to do with temperature ratings.

Now it all comes together. This is good information.

Codes, in my opinion, mean anything if you don’t understand why they were created.

So, the fast & simple answer to why PVC pipe is not acceptable for interior water distribution is:

PVC pipe is not rated for Hot Water & a code inspector is unable to quickly or easily distinguish if a distribution line is a hot or cold water line.

The additional information about how plumbing is tested is great to know about, Thanks.

This bothers me.

I understand and agree with everything said so far.
My problem is, we are not supposed to be doing code inspections.
We are supposed to be inspecting to alert clients of possible safety hazards and property damage.
How can we defect PVC pipe on a cold water line when there is nothing wrong with it except that it is a code violation?

Maybe its just me, but I’m going to have a hard time trying to explain to a client why I defected the PVC.

I have to agree with you about the CODE thing but, a lot of what we do does overlap with code. That is also why I wanted to know if anyone had any kind of a timeline of the codes. If at some time PVC was acceptable to use indoors on distribution lines then I could suggest changing it as a good upgrade…

In the example that was given here PVC fittings were used on CPVC pipe. They are not compatable and should never be glued together. The O.D. of the one pipe is different then the I.D. of the other pipe. It will leak eventually. It’s just a mater of time.

Without codes, we would have nothing to base our recommendations on.

Just remember this - “codes” are the bare minimum requirements for a residence to be legally habitable. Anything less, is “illegal.”

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All other codes that I can think of have something to do with safety or preventing damage.
I cant think of anything that is a code without a reason.
How does legal have anything to do with a home inspection? We have no authority.

The purpose of the building codes, as stated in the IRC, is to “safeguard the public.”

As Jeff Pope is indicating, Buildings built under the Code requirements of the IRC would or could endanger the occupants, and therefore, our inspections for the condition of the house along with the safety of the occupants all revolve around the bare minimum requirements of the Code.
As we can not enforce it because we are not Code Enforcement Officers, we can use it to compare it’s requirements to existing conditions that we may observe, and note whatever would condone to the hazards caused by such deviation of that Code.

Hope this helps.

Marcel :slight_smile: :slight_smile:

Wesley, my mothers house has PVC installed for the cold supply in her house. Should never have been installed but the house is in the country and no code inspections required. To make a long story short her water heater in the attic would always leak at the fittings were the flexible lines connect to the pvc supply line. She must have had different repair companies fix it ten different times until I told her to take the pvc out and install copper at this line. The leak went away. The temperature in the attic was affecting these fittings. I dont want to be the inspector with the customer calling up to want the house entirely re plumbed.