Crush-Type Seal for Plastic Tapered Pipe Threads?
Crush-Type Seal for Plastic Tapered Pipe Threads?
(OP)
Has anyone ever heard of using a crush seal, or some sort of o-ring seal on a tapered thread connection? I've always been of the opinion that a tapered pipe thread connection, by its very nature, precludes using a crush seal.
I am having a problem with plumbing leaks (liquid at 3 psi) between PTFE pipe connections and PVDF pipe connections (and PVDF pump head). The leaks start after several days, and reappear weekly. I believe it is because of the difference in durometer, between the two materials, and I may be experiencing some creep or cold flow in the softer teflon threads after tightening. Does this sound like a reasonable assumption? We are using teflon tape also. The crush seal was suggested as a solution, but I have my doubts that the concept can be effectively applied in a tapered pipe thread situation.
Under the circumstances, using identical plastics is not an option. Nor is using flared compression fittings. So I'm wondering if anyone has ever seen a successful application of o-rings or crush seals in a plastic taper thread?
I have included a pic of the leaking system, just for the heck of it. Nearly all the connections begin to leak after some days.
I am having a problem with plumbing leaks (liquid at 3 psi) between PTFE pipe connections and PVDF pipe connections (and PVDF pump head). The leaks start after several days, and reappear weekly. I believe it is because of the difference in durometer, between the two materials, and I may be experiencing some creep or cold flow in the softer teflon threads after tightening. Does this sound like a reasonable assumption? We are using teflon tape also. The crush seal was suggested as a solution, but I have my doubts that the concept can be effectively applied in a tapered pipe thread situation.
Under the circumstances, using identical plastics is not an option. Nor is using flared compression fittings. So I'm wondering if anyone has ever seen a successful application of o-rings or crush seals in a plastic taper thread?
I have included a pic of the leaking system, just for the heck of it. Nearly all the connections begin to leak after some days.





RE: Crush-Type Seal for Plastic Tapered Pipe Threads?
RE: Crush-Type Seal for Plastic Tapered Pipe Threads?
RE: Crush-Type Seal for Plastic Tapered Pipe Threads?
I've had some success using these with metallic piping. No experience with plastic.
regards,
donf
RE: Crush-Type Seal for Plastic Tapered Pipe Threads?
Be careful when you use these on PVC, PP etc.- make sure the sealant is compatible with the piping material. Some are, some most definitely are NOT and cause embrittlement, spot welding etc. of certain plastic materials.
RE: Crush-Type Seal for Plastic Tapered Pipe Threads?