Threaded PVC problem

CeeGee

CeeGee

New member
I am trying to make a stand using PVC. I bought the parts and I had to use a elbow that has two slip sides and one threaded side. On the treaded side I had to get a threaded coupling to allow me to attach additional PVC to make the stand the correct height. All of that is fine.

The problem is that when I try to tighten the threaded piece it gets tight very quickly. I would like to tighten it all the way so that I can make the stand even. Hopefully that make sense. I have included pics of what I have and what I am trying to do. I don't know if there is some kind of lubrication that would be reef safe that I can use to tighten the pieces together or if I could heat the elbow to allow the threads to loosen a little.

Thanks for any help. Sorry for the pic quality I took them with my cell phone.

The Parts
pvc_1.jpg


The point where it gets too tight
pvc_2.jpg


A quick mockup of what I am trying to accomplish
pvc_3.jpg
 
You could try cutting a 1/4" to 1/2" off the male fitting.

I'm no plumber but I believe they're tapped to get tighter so they seal easily with tape.
 
<a href=showthread.php?s=&postid=15037833#post15037833 target=_blank>Originally posted</a> by scrombussquared
A little petroleum jelly will be fine.
Click to expand...

petroleum jelly won't contaminate the water?

<a href=showthread.php?s=&postid=15037841#post15037841 target=_blank>Originally posted</a> by THE ROOK
You could try cutting a 1/4" to 1/2" off the male fitting.

I'm no plumber but I believe they're tapped to get tighter so they seal easily with tape.
Click to expand...

That may work. I will give it a try as well.
 
NPT threads are tapered. The whole idea is that the taper causes the parts to bind (and thus seal) BEFORE the parts bottom out. There's really no way to get it tighter without distorting the parts. Lubrication will help a bit, but you won't be able to bottom out the fitting without either deforming it or breaking it.

I'd try to heat the female fitting in boiling water for a few minutes, then thread it on. Wear gloves!
 
<a href=showthread.php?s=&postid=15037888#post15037888 target=_blank>Originally posted</a> by der_wille_zur_macht
NPT threads are tapered. The whole idea is that the taper causes the parts to bind (and thus seal) BEFORE the parts bottom out. There's really no way to get it tighter without distorting the parts. Lubrication will help a bit, but you won't be able to bottom out the fitting without either deforming it or breaking it.

I'd try to heat the female fitting in boiling water for a few minutes, then thread it on. Wear gloves!
Click to expand...

Maybe I could sand the Male threads down a little?
 
<a href=showthread.php?s=&postid=15037911#post15037911 target=_blank>Originally posted</a> by CeeGee
Maybe I could sand the Male threads down a little?
Click to expand...

Probably not a good idea. The rough surface from sanding would create a lot of extra friction, and by the time you sanded the taper out, you would have destroyed the threads. I'd either gently heat the parts to soften them, or just buy the furniture PVC Stu linked to.
 
You guys are right. The problem is that my Lowes didn't have any all slip fitting and I don't want to wait til next week for the ones Stu linked to get here. Plus it would cost more in shipping than the actual parts.
 
Use a teflon tape. I've tried dry fitting threaded PVC and it would bind. Wrap the threads with teflon tape and the piece goes together without the binding problem.
 
+1

take a large monkey wrench or plumber's wrench and hold the adapter (bottom piece in your pic) tightly. Take a long screwdriver and insert it into the Tee so that you are able to use the screwdriver as a lever to turn the piece.

Use the teflon tape mentioned and with the added leverage of the long-handled screwdriver, you will be able to fully seat it.

Done it plenty of time
 
luv951

"Done it plenty of time"

Yeah, I'd like to see pics of that one.



SORRY to all above with suggestions BUT:

You just CANNOT tighten a Pipe fitting all the way down. It is not meant to.
If you try hard enough, you CAN crack the female fitting though.

If you want a PVC fitting that can tighten all the way, look in the electrical section in HD or Lowes for Conduit fittings.
They are straight threads not pipe threads ( you will only find it in gray though ).

Stu
 
<a href=showthread.php?s=&postid=15040960#post15040960 target=_blank>Originally posted</a> by stugray
luv951

"Done it plenty of time"

Yeah, I'd like to see pics of that one.



SORRY to all above with suggestions BUT:

You just CANNOT tighten a Pipe fitting all the way down. It is not meant to.
If you try hard enough, you CAN crack the female fitting though.

If you want a PVC fitting that can tighten all the way, look in the electrical section in HD or Lowes for Conduit fittings.
They are straight threads not pipe threads ( you will only find it in gray though ).

Stu
Click to expand...

Is the material the same? I don't really care about the color.
 
<a href=showthread.php?s=&postid=15040903#post15040903 target=_blank>Originally posted</a> by luv951
+1

take a large monkey wrench or plumber's wrench and hold the adapter (bottom piece in your pic) tightly. Take a long screwdriver and insert it into the Tee so that you are able to use the screwdriver as a lever to turn the piece.

Use the teflon tape mentioned and with the added leverage of the long-handled screwdriver, you will be able to fully seat it.

Done it plenty of time
Click to expand...
<a href=showthread.php?s=&postid=15038677#post15038677 target=_blank>Originally posted</a> by EverettReef
Use a teflon tape. I've tried dry fitting threaded PVC and it would bind. Wrap the threads with teflon tape and the piece goes together without the binding problem.
Click to expand...

Yes the teflon tape will greatly increase the lubricity between the parts... allowing you to tighten them down to the point that stress failure will be a certainty :)
 
CeeGee,

"Is the material the same?"

Yes it is gray PVC. Glues & cuts just like regular PVC pipe.


BeanAnimal,

"allowing you to tighten them down to the point that stress failure will be a certainty"

Yes, my observation exactly ;-)


It is just impossible to tighten two pipe fitting threads all the way.
If you have ever done it, then you were the one running the pipe thread machine ( incorrectly ) ...;-)

Stu
 
<a href=showthread.php?s=&postid=15042509#post15042509 target=_blank>Originally posted</a> by BeanAnimal
Yes the teflon tape will greatly increase the lubricity between the parts... allowing you to tighten them down to the point that stress failure will be a certainty :)
Click to expand...

Not if you don't over tighten. If the OP is just trying to get within a quarter inch, the teflon tape will allow him to get multiple pieces tightened to the required tolerance. Best option is to use slip instead of threaded connectors, but if he is stuck with threaded, the teflon tape should allow him to do what he needs done. No screwdriver required. Just a two slip joint pliers.
 
To the OP -

I made a couple stands the same way you are, with threaded couplings into the elbows. This may seem too obvious and easy, but just make sure your pipes for those pieces using the couplings are all the same length. Keep all the couplings on the same "axis" and you'll be able to level the stand by tightening/loosening them small amounts. For example, keep all the couplings on the pipes that will be in the vertical position, rather than mix & matching them on horizontal pipes too. It's pretty easy to level the stand this way.
 
<a href=showthread.php?s=&postid=15040903#post15040903 target=_blank>Originally posted</a> by luv951
+1

take a large monkey wrench or plumber's wrench and hold the adapter (bottom piece in your pic) tightly. Take a long screwdriver and insert it into the Tee so that you are able to use the screwdriver as a lever to turn the piece.

Use the teflon tape mentioned and with the added leverage of the long-handled screwdriver, you will be able to fully seat it.

Done it plenty of time
Click to expand...

Worked flawlessly! I appreciate it. Looks like someone owes you an apology ;)

The stand is built and the new skimmer goes online tomorrow when I get in from work!
 
Last edited:
Glad I could help.

You seem to have accomplished the "impossible". Or, were you running the threading machine in your spare time?

Sorry, stu, couldn't resist :D
 
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