Threaded PVC problem

[CeeGee]

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
http://www.gentryillustration.com/images/reefcentral/pvc_1.jpg

The point where it gets too tight
http://www.gentryillustration.com/images/reefcentral/pvc_2.jpg

A quick mockup of what I am trying to accomplish
http://www.gentryillustration.com/images/reefcentral/pvc_3.jpg

[scrombussquared]

A little petroleum jelly will be fine.

[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.

[stugray]

You need these:

http://www.usplastic.com/images/products/pipe/28225p.jpg

http://www.usplastic.com/catalog/product.asp?catalog_name=USPlastic&category_name=28612&product_id=28641

Stu

[CeeGee]

<a href=showthread.php?s=&postid=15037833#post15037833 target=_blank>Originally posted</a> by scrombussquared
A little petroleum jelly will be fine.

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.

That may work. I will give it a try as well.

[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!

[CeeGee]

<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!

Maybe I could sand the Male threads down a little?

[Superstretch18]

PVC is cheap enough that I would just buy the exact pieces that I needed...

[der_wille_zur_macht]

<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?

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.

[CeeGee]

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.

[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.

[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

[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

[CeeGee]

<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

Is the material the same? I don't really care about the color.

[BeanAnimal]

<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
<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.

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 :)

[stugray]

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

[EverettReef]

<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 :)

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.

[driftin]

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.

[CeeGee]

<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

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!

[luv951]

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

[stugray]

CeeGee,

"Worked flawlessly!"

SO you were able to tighten two "Pipe fittings" until there were no threads showing?

Again, I would like to see a picture.


In my experience, you will spilt the female fitting before you get anywhere close.

"Looks like someone owes you an apology"

It appears that we misunderstood the question.

It is IMPOSSIBLE to thread a MPT 100% into a FPT fitting for that would defeat the purpose.

If you did so, then I will apologize to luv951 and never buy that brand of PVC fitting.

Stu

[stugray]

Ok,

Official apologies to luv951.

I just, as an experiment, took two 1-1/4" PVC threaded fittings, and I WAS able to tighten them 100% and then loosen them without breaking.

I used teflon paste, a few grunts & farts ( maybe even a hernia ).

So... it is possible.

However it is never a good idea to overtighten PVC threaded fittings.
Most of the time they break immediately and often days or years later.

So for CeeGee.s application, no worries it is not under pressure.
Glad you could make it work.


luv951 - Sorry you were correct.
I will curtail my use of the word "Impossible" ( you think i'd have learned by now ;-)

Stu

[luv951]

stu - no worries at all. I appreciate you owning up. Its all kewl.

[dogstar74]

Oh man, I was about to get out a picture. "Only a sith lord works in absoultes"

Just kidding, Even though it's not impossible, it's dang near impossible. I'm sure that's what you meant Stu.

Aaron

[BeanAnimal]

If you take a look back at what I said...

The teflon tape greatly increases the lubricity between the parts, allowing them to be severely overtightened. This puts tremendous stress on the female part. The stress may break the part immediately, or some time down the road.

In this case, a cracked fitting will not likely be a problem. However, the important information to walk away with is that it is NOT good practice for fittings that will be a problem if they leak :)

[luv951]

<a href=showthread.php?s=&postid=15049307#post15049307 target=_blank>Originally posted</a> by BeanAnimal
If you take a look back at what I said...

The teflon tape greatly increases the lubricity between the parts, allowing them to be severely overtightened......However, the important information to walk away with is that it is NOT good practice for fittings that will be a problem if they leak :)

Agreed. This is why you need to add leverage with some sort of extended handle to get the part to twist in.

[BeanAnimal]

I think you entirely missed the point... your statement is not in agreement with what I was attempting to convey :)

Without the tape, the fittings get tight very quickly, this is because they are tapered. By using the PTFE tape or paste, the parts are lubricated and can be tightened much further, putting tremendous stress on them.

When assembling threaded PVC parts, one should hand tighten the parts without tape or paste, counting the number of turns. Once the parts are dry fitted they should be disassembled and taped (or doped with paste). Final assembly should be done using the same number of turns that created a tight dry fit and then another 1 to 1.5 turns max. Going any further deforms the fittings and can cause more of a chance of leaking and/or part failure (immediate or future).

[dogstar74]

I agree that is the important information to take away, and if I ever have an application that I NEED to have the threads fully enclosed, I always take a trip down the electrical isle and use the grey fittings.

Not for arguement's sake, but for information sake, the last time I bottomed out a NPT 1/2 schedule 40 fitting with TFE tape, it was not on purpose, and I really didn't have to force it too much. I was just tightening it down and then "wow, it went all the way in." Then I thought to myself, "Boy that looks pretty sharp!" :D

L8R
Aaron

[BeanAnimal]

Yup it depends on the tolerances and manufacture of the fittings. That is also why threaded PVC (especially in sizes less than 4" or so, pretty much sucks. The cast threads are just not accurate and shrinkage, mold flash and design tolerances make things unpredictable. FWIW PTFE paste is almost always a better idea than the PTFE tape :)

[luv951]

<a href=showthread.php?s=&postid=15049568#post15049568 target=_blank>Originally posted</a> by BeanAnimal
I think you entirely missed the point... your statement is not in agreement with what I was attempting to convey :)



Actually, I think you are assuming too much about my posts. :D

This thread has been about fully seating threaded PVC for a stand. Not a pressure application. The OP just wanted to know how to make his stand level. The assertion that fully seating a threaded PVC is "impossible" is wrong. I was merely helping the OP accomplish the task that he needed help on. Never made any assertions or claims as to whether one would want to, or should want to, fully seat threaded PVC in a pressure situation. In that regard, I agree with you.

[BeanAnimal]

<a href=showthread.php?s=&postid=15051466#post15051466 target=_blank>Originally posted</a> by luv951
Actually, I think you are assuming too much about my posts. :D No, I read them word for word without assuming anything. If you meant differently, then your meaning was not clear :)

This thread has been about fully seating threaded PVC for a stand. Not a pressure application. I am very aware of what the thread is about. The advice I offered (and Stu offered) was given as "best practice" advice to aid those who read [sic] "put tape on the pvc fittings and crank them down with a cheater bar until they bottom out" and then subsuquently applied that advice to their PLUMBING as well. I made my context very clear.

The OP just wanted to know how to make his stand level. The assertion that fully seating a threaded PVC is "impossible" is wrong. I, in no way said, implied or aluded to the notion that fully seating the threads was "impossible" or even hard. I simply said that overtigthening threaded PVC fittings puts tremendous stress on them and leads to deformation and/or failure. I offered a general rule of thumb to judge how far to tighten them in a plumbung situation and also offered that for OPs purpose, a cracked fitting would likely not make a difference.


I was merely helping the OP accomplish the task that he needed help on. Never made any assertions or claims as to whether one would want to, or should want to, fully seat threaded PVC in a pressure situation. In that regard, I agree with you. Nobody has faulted you for helping. A few of us have simply offered to put context to the advice in hopes of helping the OP and others understand the ins and outs of threaded PVC connections. If you agreed with my advice, your post did not convery that meaning very clearly at all.

No hard feelings, we are all on the same side here (trying to help people learn how to do things correctly).