n unions.- Hide quoted text -
I used one ot them (real name is "Dressler Coupling") to connect/ disconnect my irrigation puimp feeding out of a stram. Eventually it 'cold formed' the PVC pipe into a 'depression' where the gasket fit. Took yeas to do it though. I don't think I would ever use one on PVC pipe in a buried application. I do have a couple of the galvanized ones in service, one over 20 oyears, with no problems...yet.
Harry K
Normal repair couiplings require at least one of the two ends be movable back and forth. A compression one can be fitted if all you can do is move one of the pipes sideways.
Harry K
I agree. I did not buy a *compression fitting* (it was my mistake to use that word). I bought a schedule 80 *union* (they don't seem to make them in schedule 40 where I live) - and a funky slider slider coupling.
Googling, I find it's actually called an *expansion coupling"
It's only rated at 200 psi though:
No, a repair coupling does not require that one of the pipes move sideways. To replace a section of pipe with a hole, you cut out that section. You cut a new piece of pipe about
1/4" shorter. You prime, put on glue. On the existing pipe you only apply glue to the usual length. On the new piece of pipe you apply primer/glue along enough of it so that the repair couplings can be slid ALL THE WAY ON. Put pipe in place, slide couplings half way back so that they are now over the old pipe.
I was looking for people's experience in using this "telescopic coupling" aka *expansion coupling*.
It looks like the DIY pool repair guy here did exactly what I did:
He *bought* the same coupling that I did; he took it apart, and looked at where the single o-ring was - and given that it's on the *end* of the slider pipe, he concluded, as I did, that it might not hold pressure as well as a union would.
I find out here that even the really fancy ones with multiple Viton/EPDM o-rings (over $300 each!) are rated only to about 235 PSI:
Now that I've taken the thing apart and compared it with a union, I think that in certain applications they might be great. For example, if your pipes *move* in use, and if you're below 200 psi, they might be useful.
Also, in my case, I knew I had limited clearance between the bottom of the pipe and the concrete slab - so I had reasoned (in the store) that it was "thinner" at its greatest width than a normal schedule 80 union was.
It turns out though that the schedule 80 union just about made it, so I had room enough for that "fatter" union. Plus, when I took the expansion coupling (aka telescopic coupling) apart, I was worried that the o-ring, which goes around the end of the sliding pipe, was directly in the path of the onrushing water - and I reasoned that it could cause turbulence compared to the little nub on the inside of the union - and - worse yet - it might leak since the o-ring is directly in the path of the onrushing water.
Googling for the PSI of a 2 inch union, I am dismayed that they are only pressure rated to 150 psi:
So, I guess, in hindsight, *both* unions and expansion couplings don't handle high PSI. (I forget what the PSI is in the pool pipes though.)
I found out later that you are correct. It's known as a 2-piece "expansion coupling" or "telescopic coupling".
Lowes sells them as: CARLON 2-in Schedule 40 PVC Coupling Item #: 72268 | Model #: E945J-CAR
Apparently they're useful to "compensate for length changes due to temperature variations".
In my case, there were no length changes over time; so it was overkill.
*The Carlon model is for electrical conduit only and is used for PVC electrical conduit that is subjected to temperature variations because PVC expands and contracts as the temperature changes.
Ooops. My mistake.
I had googled for expansion couplings and I had not realized those that I had found at Lowes (for half the price that I had had paid for mine) were for electrical connectors. Thanks for pointing that out.
That also explains the low price (about $8), which alone should have clued me in as mine was almost double that price.
So one of the cons of these 2" PVC (fluid) expansion couplings is cost.
I need to repair this hole, which was plugged by whomever removed the automatic chlorine feeder; but it sometimes leaks:
I don't understand how it can be done, even after reading your description. The 1/4 inch won't be enough.
I think you're saying to fix this, I can:
That's the only way I see that it can be done, and, even this method has a problem that you can't shove the pipe straight in on the first side.
So I must be missing something on how to repair a section without a union.
Here is a picture of the o-ring location of the union versus the telescopic slide:slide coupling:
Notice the location of the o-ring in the expansion coupling is in line with the fluid, while that of the union is off to the side.
you could have turned the expansion one around so that it flowed with the water
I used to see some on pipe for pivot irrigation systems. It's been a long time ago though. Water supply pipe for pivots is usually
8" in the central U.S. There is some 10" but it's pretty uncommon around here. There really is no need for them since there is usually an elbow or something one can remove to get pipe apart.
That might help; but it's still inline with the water flow, whereas the union is off the flow direction (AFAIK).
Still - that would have been a good idea had I used the expansion coupling for the repair.
Next repair I'm going to try just couplings and pipes, to see if it can be done without a union.
DADD-
I guess the results of your "Googling" means that
flexpvc.com is wrong when they call the item a PVC-Couples- Telescoping?
btw 200psi isn't enough for your pool application?
that in certain applications they might be great. For example, if your pipes *move* in use, and if you're below 200 psi, they might be useful.
DADD-
You're preaching to the choir.... I know exactly how these things are designed & how they work.
They work just fine otherwise you'd find tons of complaints about them.
Your concern about "O-ring in the expansion coupling is in line with the fluid" is unfounded, more novice / non-mechanically inclined hand wringing.
+1
good point but the o-ring is not vulnerable to the water flow in any case
whereas the union is off the flow direction (AFAIK).
Let's say you have 3 ft of pipe with one 6" section near the middle that's bad. You cut out the 6" piece. You cut a new piece about 1/4" shorter. Now it will fit easily where the bad piece was. You prime/glue all 4 ends of the pipes and the two repair couplings. You slide the repair couplings ALL THE WAY ONTO THE 5 3/4" repair pipe. Now what you have is still 5 3/4" in length. You position the repair pipe with the couplings where it goes, then slide the two couplings into place over the ends of the existing pipe.
Thanks for being patient with the explanation.
I understand the key point, which is you make a temporary double-ended "slider" out of the repair 5-3/4pipe, where it fits inside the 6" opening, and then, while the glue is still wet, you slide the still-wet couplings (before they have set) out to meet the old pipe on both ends.
This is ingenious!
The only problem I have is with the math on the initial length of the
5-3/4 inch repair pipe - but that's a minor concern as the idea is what matters.(I'll take up the length clarification separately.)
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.