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Posted: 5/31/2022 11:48:23 AM EDT
[#1]
For ease of disassembly, would a 3-piece coupling (swede, ericsson, UNF, union, etc...) work?...
ETA:  ...
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Posted: 5/31/2022 11:49:56 AM EDT
[#2]
For threaded connections, I just use tape. I'm not a plumber, though.
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Posted: 5/31/2022 12:00:29 PM EDT
[#3]
Quoted: Just like the title says, I have two whole house water filtration systems I need to install in my place. Main floor and lower floor with inlaw quarters. Water is supplied by triple 40k cisterns so each system will have a UV unit, a coarse and carbon cartridge filters. My question is I have a few NPT connections that are PVC to PVC, I need opinions on how I should seal the threads. With the ability to disassemble the connections in the future. Pipe sealant only Teflon tape only Or both sealant and tape The remaining connections are PVC to PVC slip fittings (glued) PVC to PVC threads can be problematic though and it's not something we run across often in the type of work we do. If it were in my house and no one was watching, I'd use T-tape and Rectorseal #5. It certainly won't hurt anything. ETA; the post suggesting using a union for future disassembly is a good idea. |
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Posted: 5/31/2022 12:05:36 PM EDT
[#4]
We had a pool with several threaded pvc connections
A guy I hired to fix something used "pool & spa lube" Fixed the leak |
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Posted: 5/31/2022 12:08:19 PM EDT
[#5]
Actually a few unions that I'm using on this project have one end slip/glued the other end is threaded so I can remove the filters or UV unit later because those are female NPT threads.
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Posted: 5/31/2022 12:08:44 PM EDT
[#6]
Use a union, otherwise you are going to need to be able to spin the whole thing.
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Posted: 5/31/2022 12:10:11 PM EDT
[#7]
Thread tape, if you use pipe dope just remember "little do a little good, lot will do alotta good".
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Posted: 5/31/2022 12:14:29 PM EDT
[#8]
Teflon tape. As stated previously I’d use unions for future disassembly.
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Posted: 5/31/2022 12:18:12 PM EDT
[#9]
I do some sprinkler system work, I have had good luck w/ Teflon Tape w/ some waterproof grease sparingly used as a lube.
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Posted: 5/31/2022 1:05:09 PM EDT
[#10]
That's what I was wondering if mating two threaded PVC fittings together would cause the connection threads to seize during assembly or removal.
During my working days mating stainless NPT fittings was always problematic, you seemed to always use tape and dope or you could never get them apart. |
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Posted: 5/31/2022 1:12:01 PM EDT
[#11]
Another vote for the couplers.
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Posted: 5/31/2022 1:16:18 PM EDT
[#12]
Quote HistoryQuoted: I am a plumber and have been for a very long time. Normally I say use one or the other. I don't believe in using tape or dope for good luck. One or the other on tapered threads only. PVC to PVC threads can be problematic though and it's not something we run across often in the type of work we do. If it were in my house and no one was watching, I'd use T-tape and Rectorseal #5. It certainly won't hurt anything. ETA; the post suggesting using a union for future disassembly is a good idea. |
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Posted: 5/31/2022 1:25:43 PM EDT
[#13]
I'd go with unions where I could if future disassembly will be required.
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Posted: 5/31/2022 1:33:57 PM EDT
[#14]
PVC is a poor choice for potable water.
Type of thread sealant does not matter just use one or both. |
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Posted: 5/31/2022 1:54:00 PM EDT
[#15]
Teflon rectorseal, the white stuff or if I'm using Teflon I like the fastape. Thicker, takes less wraps and doesn't ball up.
Pipe dope is one of the few times in life it's good to be liberal |
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Posted: 5/31/2022 2:12:24 PM EDT
[#16]
I would use pipe sealant, I found it works better than tape at stopping the drip leaks.
I base this on some plumbing work I just did, tried the tape first, it leaked, I then used the sealant, no leak. |
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Posted: 5/31/2022 2:15:27 PM EDT
[#17]
So I actually do a bit of failure analysis and expert witness work in this area. First off, never go metal male thread into a plastic female thread, that is asking for trouble. Only use plastic males in plastic females. Secondly, I would recommend pipe thread tape. Certain thread compounds or sealants appear to be damaging to PVC. With PTFE tape, you are virtually assured not to have degradation issues.
Edit: Do not do both. And make sure that you are applying the tape properly, i am sure there are tutorials on how to do this out there. |
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Posted: 5/31/2022 2:18:10 PM EDT
[#18]
Quote HistoryQuoted: I am a plumber and have been for a very long time. Normally I say use one or the other. I don't believe in using tape or dope for good luck. One or the other on tapered threads only. PVC to PVC threads can be problematic though and it's not something we run across often in the type of work we do. If it were in my house and no one was watching, I'd use T-tape and Rectorseal #5. It certainly won't hurt anything. ETA; the post suggesting using a union for future disassembly is a good idea. Some dopes are not plastic pipe safe. PTFE dope is usually plastic pipe safe. |
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Posted: 5/31/2022 2:21:42 PM EDT
[#19]
Quote HistoryQuoted: We had a pool with several threaded pvc connections A guy I hired to fix something used "pool & spa lube" Fixed the leak 
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Posted: 5/31/2022 4:00:54 PM EDT
[#20]
Size also matters. Up to 1" I'd use tape. Above that, always dope. I could check my brand, but we use a ptfe sealant adhesive that is food safe and works great. You can thread it in by hand and it's sealed.
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Posted: 5/31/2022 4:22:25 PM EDT
[#21]
Slick-Tite pipe dope.
Or Universal joint glue and cut it apart when replacing filter housing becomes necessary. |
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Posted: 6/1/2022 10:31:29 AM EDT
[#22]
Quote HistoryQuoted: So I actually do a bit of failure analysis and expert witness work in this area. First off, never go metal male thread into a plastic female thread, that is asking for trouble. Only use plastic males in plastic females. Secondly, I would recommend pipe thread tape. Certain thread compounds or sealants appear to be damaging to PVC. With PTFE tape, you are virtually assured not to have degradation issues. Edit: Do not do both. And make sure that you are applying the tape properly, i am sure there are tutorials on how to do this out there. I was wondering about this issue if you thread a metal nipple into a plastic female connection the metal nipple puts a expansion type constant force into the plastic when you connect the joint, then as the plastic ages it finally splits. |
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Posted: 6/1/2022 11:35:28 AM EDT
[#23]
Quote HistoryQuoted: I was wondering about this issue if you thread a metal nipple into a plastic female connection the metal nipple puts a expansion type constant force into the plastic when you connect the joint, then as the plastic ages it finally splits. Just don't over-tighten, and use a sacrificial bushing. Sometimes material combinations are not easy to avoid. Also check the threads before installing, some of the el-cheapo products have mold lines or poor threads that need to be addressed. External thread files are 10-15 bucks. PVC / CPVC is fine for water, NSF 61 marked products of course. I prefer sch80, but that's for work stuff. |
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Posted: 6/1/2022 11:45:24 AM EDT
[#24]
Rare for me to even use male threaded pvc couplers. They break to damned easy where the threads meet the body.
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Posted: 6/1/2022 12:14:07 PM EDT
[#25]
Best way to seal threaded pvc water connections is to not use pvc for water connections.
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Posted: 6/1/2022 12:25:53 PM EDT
[#26]
Quote HistoryQuoted: PVC is a poor choice for potable water. Type of thread sealant does not matter just use one or both. Why? Pretty common meter to structure runs on utility water and almost every well system will utilize some PVC. |
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Posted: 6/1/2022 12:26:36 PM EDT
[#27]
Own a plumbing company.
We use thread sealant AND Teflon on all thread connections for water and gas. But also we don’t use threaded PVC for water. Or really pvc for anything except drains. Never for pressure. |
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Posted: 6/1/2022 12:31:00 PM EDT
[#28]
Tape is good if the threaded connection feels a little loose. Using tape when it's already a tight connection leads to too much torque needed to get enough thread engagement. Otherwise just use Rectorseal. Tru blu version works fine for me - vibration resistant and potable water safe. https://rectorseal.com/rectorseal-tru-blu-group/
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Posted: 6/1/2022 1:11:58 PM EDT
[#29]
Both pipe dope and tape attempt to achieve the same purpose. They are both used to LUBRICATE the threads so that they can be inserted farther and tighter into the fitting, thus melding the male and female threads together more.
If you use no tape or dope, you can still crew the two fittings together, but they do won't meld as much to each other due to friction causing too much heat. Tape and dope help reduce the friction, allowing the THREADS to seal better. Both dope and tape are fine, and they also form a secondary seal at the joint where the threads end at the pipe (see below). Now, on old metallic pipe that is eroding/corroding, pits will develop in the piping and if you are screwing a male thread into an old female fitting, it may be better to use dope because it can get in the pits better than tape. I have also seen people use fibrous twine in connection with dope to help seal really old metallic piping. There is really no reason to use BOTH dope and tape unless it makes you feel more comfortable with your work. Pipe with dope/tape before entering a fitting is on the left. On the right is what happens when the male thread is screwed into a female fitting. The tape/dope does NOT stay on the male threads. It squeezes outside of the joint. If one were to put dope on the female threads, it could be pushed into the fitting causing debris to enter the pipe.  Attached File |
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Posted: 6/1/2022 3:24:04 PM EDT
[#30]
Handful of sand.
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Posted: 6/4/2022 10:06:00 AM EDT
[#31]
Quote HistoryQuoted: Both pipe dope and tape attempt to achieve the same purpose. They are both used to LUBRICATE the threads so that they can be inserted farther and tighter into the fitting, thus melding the male and female threads together more. If you use no tape or dope, you can still crew the two fittings together, but they do won't meld as much to each other due to friction causing too much heat. Tape and dope help reduce the friction, allowing the THREADS to seal better. Both dope and tape are fine, and they also form a secondary seal at the joint where the threads end at the pipe (see below). Now, on old metallic pipe that is eroding/corroding, pits will develop in the piping and if you are screwing a male thread into an old female fitting, it may be better to use dope because it can get in the pits better than tape. I have also seen people use fibrous twine in connection with dope to help seal really old metallic piping. There is really no reason to use BOTH dope and tape unless it makes you feel more comfortable with your work. Pipe with dope/tape before entering a fitting is on the left. On the right is what happens when the male thread is screwed into a female fitting. The tape/dope does NOT stay on the male threads. It squeezes outside of the joint. If one were to put dope on the female threads, it could be pushed into the fitting causing debris to enter the pipe. https://www.ar15.com/media/mediaFiles/336822/threads_jpg-2404259.JPG That's because you used too much tape. |
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