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    What are Schedule 40 and Schedule 80 ratings for pipe?

    Asked Jul 6, 2006, 12:48 AM 15 Answers
    Ok, pvc is temperature restricted to 140 F so no hot water, cpvc can be used in the house. What is schedule 40 and schedule 80?

    Last edited by CliffARobinson; Aug 17, 2011 at 05:05 PM.
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    RickJ's Avatar
    RickJ Posts: 7,764, Reputation: 864
    Uber Member

    Jul 6, 2006, 02:50 AM
    In the United States, "Schedule" refers to the thickness of the pipe wall and, therefore, how much pressure it will hold. In most aquaculture applications, Schedule 40 is used because:

    1. It works for most applications and is readily available.
    2. In small quantities, it is only slightly more expensive than the thinner wall Schedule 120.
    3. The wall is thick enough so that it will not distort when walked on.
    4. From 1/2" to 2", it is rated at no less than 140 psi at 73°F. The highest pressure typically found at any facility is 65 psi, which is the average city water supply.

    Schedule 80 is rated at no less than 200 psi at 73°F (up to 2") and is usually gray (similar to the Schedule 40 pipe used for electrical conduit).

    There are very few reasons to ever need such a heavy, costly pipe for aquaculture. The outside diameter (O.D.) is the same on Schedule 120, 40 and 80, so an expensive Schedule 80 fitting could be used on Schedule 120 or 40 pipe, if that's all that was available. As the wall of the pipe gets thicker, the inside diameter (I.D.) gets smaller. With fittings, the outside diameter gets larger.

    The main reason to use Schedule 80 is if it is mandatory in your area for specific applications but it can also be used on cold water loops to help insulate. <source>
    Helpful (2)
    afaroo's Avatar
    afaroo Posts: 3,926, Reputation: 245
    Ultra Member

    Mar 23, 2009, 11:36 PM

    I agree with RickJ, he have described very well I am attaching the following links just for information, Thanks.

    Best Regards,

    Nominal Pipe Size - Wikipedia, the free encyclopedia

    PVC and CPVC Pipes - Schedule 40 & 80
    dominicano's Avatar
    dominicano Posts: 1, Reputation: 1
    New Member

    Jul 31, 2009, 01:27 PM
    Schedule 40 in term of PSI , how much is it?
    massplumber2008's Avatar
    massplumber2008 Posts: 12,606, Reputation: 1182
    Senior Plumbing Expert

    Jul 31, 2009, 01:43 PM

    Hi Dominicano:

    The info. above is not correct. I think Rick meant to say that maximum temperature rating is 140 F... but not maximum working hydrostatic pressure... ;)

    Cellular core PVC is considered a NO PRESSURE PVC... so not to be used for pressure applications.

    The correct answer depends on the size of the schedule 40 PVC pipe. For example at 75 degrees F, 2" sch. 40 PVC pipe can work with liquid up to 280 PSI, but 3" is only rated for 260 PSI and 4" PVC for only 220 PSI, etc. These are MAXIMUMS and again are NOT for schedule 40 cellular core DWV type PVC.

    Check it out at:

    See page #25 of 112... ;)

    Let me know if you need more info...

    kbota's Avatar
    kbota Posts: 1, Reputation: 1
    New Member

    Feb 22, 2010, 08:22 PM

    Quote Originally Posted by kbota View Post
    Sorry for the double post, but my understanding of pipe schedule is that schedule 120 is extremely heavy wall, sched 80 is heavy wall, and sched 40 is standard wall thickness.
    Sched 20 is that light wall junk that's not even good for making tomato stakes.

    Check out the link.

    careypr's Avatar
    careypr Posts: 1, Reputation: 1
    New Member

    Mar 16, 2011, 12:59 PM
    What happens to the PVC pipe if the operating temperature is marginally higher than the 140. I am planning on using exisitng piping for heating a pool, but changing the heating source. The specified output temperature of the heat exchanger is 165 degrees.

    Thanks you

    btwlzyqs's Avatar
    btwlzyqs Posts: 1, Reputation: 1
    New Member

    Aug 7, 2012, 03:41 AM
    Schedule 40 Steel Pipe ,Schedule 80 Steel Pipe

    Stu Figgs's Avatar
    Stu Figgs Posts: 1, Reputation: 1
    New Member

    Sep 25, 2012, 07:12 AM
    SCH 40 NPS 16 - the external diameter is 16", the internal is 15", and the nominal thickness is 0.5 inch?? If I recall my math, from 15 to 16, there's still 1 whole Inch, not half! Haha

    Sorry for the question, I know the answer is going to be dumb, but I really want to know. Can anybody explain?
    massplumber2008's Avatar
    massplumber2008 Posts: 12,606, Reputation: 1182
    Senior Plumbing Expert

    Sep 25, 2012, 02:51 PM

    Hi Stu

    To get the external diameter to make sense using the nominal pipe size and the schedule of the wall thickness you need to add the internal diameter to the schedule of the pipe, but need to count the schedule (thickness) of the pipe TWICE to get the overall diameter of the pipe... see image below.

    Attached Images
    kari1345's Avatar
    kari1345 Posts: 1, Reputation: 1
    New Member

    Dec 31, 2012, 04:09 AM
    Hi when we designing some network for example for gas, what is the relation between pressure and sch?
    Thanks to all
    speedball1's Avatar
    speedball1 Posts: 29,303, Reputation: 1939
    Eternal Plumber

    Dec 31, 2012, 05:45 AM

    PVC isn't used for gas to the best of my knowledge, Check out the chart on post #10 on page one. Tom
    bigd1305's Avatar
    bigd1305 Posts: 1, Reputation: 1
    New Member

    Apr 7, 2013, 10:36 AM
    Will 3 inch nds fittings fit 3 inch schedule 40 pipe
    speedball1's Avatar
    speedball1 Posts: 29,303, Reputation: 1939
    Eternal Plumber

    Apr 7, 2013, 10:56 AM
    Why are you asking? What schedule are the fittings you wish to install? Back to you, Tom
    kkamaruddin's Avatar
    kkamaruddin Posts: 1, Reputation: 1
    New Member

    Apr 29, 2013, 06:00 AM
    What kind the threads NPT or BHP for sch 80
    speedball1's Avatar
    speedball1 Posts: 29,303, Reputation: 1939
    Eternal Plumber

    Apr 29, 2013, 07:50 AM
    Schedule 80 PVC fittings are standard threads at NPT. A limited range of BSP threaded fittings are available.
    Does this answer your question? Tom

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