"Live" Thin wall PVC

Discussion in 'Irrigation' started by jcom, Oct 13, 2005.

  1. jcom

    jcom LawnSite Senior Member
    Posts: 791

    We always use schedule 40 for anything that is pressurized.

    On all previous repairs, we encountered the same. On the last two repair projects, we found a company using the thin wall stuff on live lines. I told the owners I didn't find that to be too good. New homes and expensive at that. Freezing climate is probably going to tear them up in my opinion. How about ideas and opinions?

    Thanks ,

  2. Dirty Water

    Dirty Water LawnSite Fanatic
    Posts: 6,799

    Hehe...95% of the people here use SDR-35 or 21 (the so called thin/eggshell pipe) on their high pressure lines.

    I use SCH 40, because its a bit more fracture resistant, and I work in a rock infested area. If I installed in pure clay or sand all the time, I would use SDR-21...Its still rated for 200 psi.

    And for whats its worth, SDR pipe is usually more freeze tolerant than sch 40 in my experience.
  3. Green Sweep

    Green Sweep LawnSite Senior Member
    Male, from Pittsburgh, PA
    Posts: 322

    Class 200 PVC?

    That is all that we & every other irrigation contractor here in Pittsburgh use. In fact, it is very rare that I find schedule 40 while servicing systems. Usually, the only time that I see sch. 40 is if the contractor used PVC inside the home (which we do not do - copper only inside! ).

  4. jerryrwm

    jerryrwm LawnSite Bronze Member
    Posts: 1,274

    SDR-21 rated at 200 psi, and SDR 26 rated at 160 psi is fine for live pressure lines. Sch 40, SDR-21 and SDR 26 all have a hydrostatic burst pressure of 2000 psi.

    Advantages of SDR pipe - Lower friction loss at same flows and velocities. Less cost in the smaller sizes. Pressure rating remains constant from 3/4" on up to 8" and beyond. As SDR pipe size increases so does the wall thickness by the standard dimension ration (SDR) thereby maintaining the 200 psi rating. As Sch 40 increases the wall thickness also increases by not by a ratio but by an equivalent size of steel pipe. As a result Sch 40 working pressure actually decreases as the pipe gets larger. In fact at 4" SDR is 200 psi while Sch 40 is 210 psi. At 5" SDR still has 200 psi while Sch 40 is under 200.

    Advantages of Sch 40 - only one I can think of is more resistance to damage in rocky soils when pipe is pulled or if the backfilling on trenched lines is done haphazardly. It also satisfies the plumbing inspector in some municipalities who has convinced the city that Sch 40 is better.

    Apparently SDR pipe is deemed proper for large commercial applications and for golf courses where the pipe is under higher pressures and is cycled more than most residential systems ever will be. It is not the structure of the pipe that causes the problems that I have observed over the years. It is the installer that is usually at fault. Piling the dirt back in the hole including rocks and other debris which can cause puntures and abrasion over time. It takes a little more time, but a 3"-4" bed of clean backfill will save a lot of headaches down the road. As far as freeze damage Sch 40 will freeze as readily as SDR if given the opportunity. But since most systems are drained and blown out up north this shouldn't be too much of a problem.

    The only time I run across Sch 40 on the systems down here is when the system was put in by a plumber (usually 3/4" and a really crappy job) or on a homeowner installed system and they bought the parts at the box store.

    Just my $.02


    Jon do people up that way really use SDR-35? That is usually non-pressure sewer pipe.
  5. jcom

    jcom LawnSite Senior Member
    Posts: 791

    Yes, it is the thin wall stuff that I thought was only for laterals off a main line where there was dynamic pressure and not static all the time. See vent pipe the same type.

  6. PurpHaze

    PurpHaze LawnSite Fanatic
    Posts: 5,496

    Damn nice job Jerry!

    We pretty much stick to CL 200 for everything here. It will carry more water in it until you reach 6" diameter where the difference between SCH 40 and CL 200 switch places on the friction loss charts. When we get that large we usually switch to C-900 pipe anyway. You cannot buy 1/2" CL 200 here through the supply houses because it is just too thin. All the suppliers switch to CL 315 for 1/2" pipe. However, you can buy some really thin stuff at Cheapo Depot.
  7. jcom

    jcom LawnSite Senior Member
    Posts: 791

    I did not anticipate the wide difference of opinions. When I cut the thin stuff, it is just so brittle it snaps.

    I will stick with the schedule 40 for pressure lines. Just my comfort zone, I suppose. I don't use poly for live lines, no matter their rating. I will not warranty any winterizing with the thin pipe also.

    Thanks for the input, all.

  8. Rotor-Man

    Rotor-Man LawnSite Member
    Posts: 126

    Agree with you, as all I use is Sch. 40 on all my mainlines, just what I feel is right for the job regardless of the extra $3-$5 in costs. Regarding loss in pressure, I think for the most part we are talking average residental jobs here and not large commercial projects, so the pressure loss is immaterial to what the job requires.
  9. PurpHaze

    PurpHaze LawnSite Fanatic
    Posts: 5,496

    Even CL 200 in 1" and below can be tricky. especially if the weather is on the cool side. Quick dab of primer warms the pipe up and it cuts like butter. We use Klein snap-cutters for our pipe 1-1/4" and below. Lennox bone saws on 1-1/2" and larger until we have to take out the Dewalt. :D
  10. ninrocket

    ninrocket LawnSite Member
    Posts: 87

    Schedule 40 for sure on the mains....minimum 1 inch. We have in excess of 80 psi in my county. Somebody messes with a regulator....water hammer....bang! Not worth the risk.

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