Compression fittings for PE loop pipe?

Discussion in 'Geothermal Loops' started by arkie6, Jul 29, 2015.

  1. arkie6

    arkie6 Active Member Forum Leader

    Anyone use the compression fittings for PE loop pipe available from geohydrosupply?

    I'm planning on constructing my own PVC pipe loop manifold in the basement next to my geothermal unit. The 3 vertical well loops of 3/4" HDPE pipe would terminate to the PVC pipe manifold via isolation valves. I was originally going to use steel or brass barb type insert fittings to connect to the HDPE pipe but I found these plastic compression fittings for connecting 3/4" PE pipe to 3/4" PVC that thought that might be the better way to go. Just trying to get some input on any actual field experience with these fittings.



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  2. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    We have not had good luck with PVC pipe manifolds. It seems that the expansion and contraction that comes with the temperature swings plays havoc with the joints.
     
  3. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    I totally agree with above. A stab fitting to a transition to hose would be a better option IMHO. Better yet find someone with a fusion iron to rent, or pay them to fuse transition fittings on your tails. That way if something does go south, it is simply a matter of replacing things down stream of the transition from hdpe to whatever.
    Eric
     
  4. arkie6

    arkie6 Active Member Forum Leader

    Thanks for the insight. I'm curious regarding the problems with PVC pipe manifolds. Did they experience leaks or cracks? Were the problems at the glued joints or the threaded transitions to metal adapters?

    In my experience, most problems with PVC pipe are at the threaded transitions - threaded PVC female adapters over male metal pipe adapters are subject to leaks or cracking due to the internal pressure exerted by the tapered metal threads and thermal expansion of the PVC, and threaded PVC male adapters are subject to cracking at the thin root of the thread. That was my reason for looking at these compression fittings to adapt PVC pipe to PE pipe was to avoid threaded PVC-to-metal adapters where possible.

    In my proposed PVC manifold with the compression fittings above, I have one PVC-to-metal transition from the 1-1/4" sch 40 PVC pipe to the 1" rubber hose that connects to the unit. This was going to be a 1" stainless steel insert barb fitting x 1" MPT threaded into a 1-1/4" (slip) x 1" MPT adapter bushing glued into a 1-1/4" PVC coupling. I intended to use Permatex Ultra Grey RTV Silicone on the male threads of the stainless barb fitting to reduce the torque required to get a good leak tight seal in the female threaded PVC bushing.
     
  5. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    arkie,

    You are probably right about the leaks being at the threads. It has been like 5 years and I don't remember the details , other than we agreed to never do PVC again.
     
  6. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    I have some minor issues with professionally built compression fittings and manifolds. I have suff that has been trouble free for years in the field. Could be lock of the draw, pun intended. I am with Eric on the stab fittings, but you need to watch your pipe sizes.

    Mark
     
  7. arkie6

    arkie6 Active Member Forum Leader

    My loop pipes are standard 3/4" SDR-11 black poly. When you say "watch your pipe sizes" are you referring to the difference between Iron Pipe Size (IPS) and Copper Tube Size (CTS) sized plastic pipe?
     
    Last edited: Aug 2, 2015
  8. arkie6

    arkie6 Active Member Forum Leader

    All of the HDPE socket fusion adapter fittings that I have seen have fixed brass male or female pipe threads on the end that won't spin. If these are being attached to a ball valve that is attached to a manifold, do you screw the fitting into the ball valve before you fuse it to the pipe? Then, if the threaded fitting leaks, how do you tighten it or remove it to provide more thread sealant? If you had a leak at the threaded adapter, it appears to me that you would have to cut the poly pipe, fix the leaking threads, then fuse the poly pipe back together using a socket coupling.
     
  9. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    you are right about installing the ball valve first on the adapter fitting, you want to make sure that you have plenty of tape and pipe dope on the fitting.
     
  10. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    This is where the 3 way valves that you can buy or come with a flow center really shine. We make 1 transition from HDPE from the loop field to the inside work. How you get the work done past that 1 transition can be your choice. When we do DIY installs it helps us verify that the work outside passed it's testing and is solid. All inside work is waaaay easier to do over if you know the field is solid. I have seen many loop jobs terminate from HDPE to a valve followed by a T. This allows you to isolate the field from the inside work, and gives the inside work a way to purge the inside work via the T, prior to opening the inside work to the outside. If the inside work has a way to purge the small amount of air trapped in that fitting via a air escape and pressure tank or a non pressurized flow center, life is good for everyone.

    Eric
     
  11. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    Geothermal Supply does sell these fusion adapters with a swivel fitting that comes with an o-ring. They would thread right on to a PVC nipple. upload_2015-7-31_17-47-16.png

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  12. arkie6

    arkie6 Active Member Forum Leader

    Thanks for the link. I had not come across those type fittings yet.
     
  13. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    I was talking about shark bite type fittings.
     
    arkie6 likes this.
  14. arkie6

    arkie6 Active Member Forum Leader

    I've never used Sharkbite fittings, but it is my understanding they are for CTS pipe such as copper tubing, CPVC, and PEX. Schedule 40 PVC and most of the black ploy pipe used for geothermal is IPS which has a larger ID and OD than CTS of the same nominal size. Some black poly is CTS, so it can get confusing trying to keep up with the correct pipe size.
     
  15. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    Stab fittings work like shark bites, but are geo specific. True geo pipe is also sdr rated, not ips. It is close to ips, but not exactly. For that reason I frown on any ips fittings being used with geo pipe.
    Eric
     
  16. arkie6

    arkie6 Active Member Forum Leader

  17. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    Please note the difference in the I.D of the same pipe size as you wander down your provided chart. Yes they are all ips o.d. but the i.d is what varies. If a ips fitting is designed to work with a given i.d vs o.d size. how do we make up for the different i.d sizes on your chart? Answer= fusion or stab fittings designed for a given geo pipe with a given sdr rating.

    Eric
     
  18. arkie6

    arkie6 Active Member Forum Leader

    I realize that as the pipe SDR number changes, so does the ID because the OD is fixed with IPS sized pipe. IPS fittings are designed to work with the OD of the pipe, which should all be the same for a given IPS pipe size assuming it is manufactured to a standard. The compression fittings that I posted in the first post rely solely on the pipe OD for the mechanical attachment and pressure seal.
     
  19. mtrentw

    mtrentw Active Member Industry Professional Forum Leader

  20. arkie6

    arkie6 Active Member Forum Leader

    I see now that the Geo-Stab fittings are specific to SDR11 pipe and seal on the ID of pipe. I had never really looked that close at those in the past because of the cost which is 3 times as much as the compression fittings in the first post.
     

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