CPVC Coupling Question

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SAS

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How much pipe needs to go into the coupling? I have about 1" of CPVC pipe to work with if I don't want to make this a much bigger job. Is that OK?
 

Reach4

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How much pipe needs to go into the coupling? I have about 1" of CPVC pipe to work with if I don't want to make this a much bigger job. Is that OK?
I will go with (L-N)/2. Example, for 1 inch, that would be 1.19 inches.
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Gary Swart

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PVC and CPVC should bottom out in the fitting. Actually, 100% bottoming is not real required, but when you join the pipe and fitting, you should use a slight twisting motion while pushing the pipe into the fitting. Then, hold the joint together for a few seconds while the "glue" sets up. If you take the pressure off too soon, the pipe tends to push itself out a bit. A fraction of an inch would compromise the joint, but it's easy to avoid any problems.
 

SAS

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Realistically, I only have 5/8" that can be inserted into the fitting. The purpose of doing this is to replace some fittings labeled "cold water only" that connect to a check valve in a hot water recirculation system. The fittings are not leaking or showing any signs of a problem. So here are my alternatives:
  • leave the fittings as is - they have been in place for at least a couple of years, are very visible, and show no signs of any problem
  • replace the fittings by using a new fitting with only 5/8" of CPVC fit into it
  • remove the shutoff valve on the other side of that 5/8" piece of CPVC, an elbow or two and figure out how to drain everything
I know that a plumber or a very experienced DIYer would probably choose the last option, but what do you recommend for someone with less experience? The more work I have to re-do the higher the risk. How much risk is there in options 1 and 2?
 

Reach4

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If you want to get suggestions, I suggest a photo (800 pixels width and high max ). It is not clear why replacing a valve would require adding elbows, or why you have to drain something.

Your pipe has shrunk, it would seem. :) If your numbers were to have mattered, you would have needed to specify your pipe size. With 5/8, you don't have enough for even 1/2 inch CPVC.

CPVC and PVC pipe are different sizes. I guess the piece you are considering replacing is sized for CPVC size, but you might want to get a caliper and do some measurements before cutting pipes.
 

SAS

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Sorry, I don't have a camera handy, but maybe I can clear up the confusion I have created with my poor descriptions. First of all, it is 3/4" CPVC pipe. After cutting, I will only have 5/8" of pipe available to fit into a coupling. The piece of pipe is between two shutoff valves, along with the recirculation pump and the check valve. If I limit myself to staying between those two valves, I don't have much to drain. The reason I only have 5/8 inch of pipe to work with is that this pipe is attached to the shutoff valve. So if I want to replace those fittings and need more than 5/8 inch of pipe, I have to cut out that shutoff valve - hence the draining issue. Also the shutoff valve is right up against an elbow, so I would need to remove that as well. Here's a rough diagram:

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The other piece of information is that I will be replacing the pump. That is where this project started, and that is how I came to realize that the check valve was connected with fittings that are not rated for use on hot water lines.
 
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SAS

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CPVC pipe is NEVER labeled "cold water only" because using it for hot water, or the ability to use it, is the reason it is used in the first place.
Maybe I was unclear - the pipe is not labeled "cold water only", it's a CPVC male pipe thread adapter that is threaded into the check valve that is labeled "cold water only". I believe that the issue is the expansion rate of the plastic male threads vs. the expansion of the brass female threads on the check valve.
 

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If I limit myself to staying between those two valves, I don't have much to drain.
If you don't have a suitable bucket, maybe you have a plastic waste basket or something to catch water. Even a good trash bag in a laundry basket or wicker basket can hold water that you might drain. Maybe I am misunderstanding what you mean.

Maybe I was unclear - the pipe is not labeled "cold water only", it's a CPVC male pipe thread adapter that is threaded into the check valve that is labeled "cold water only". I believe that the issue is the expansion rate of the plastic male threads vs. the expansion of the brass female threads on the check valve.
You have threads on the check valve? That would seem to make replacing things, while reusing most of the parts, easier.

If I were determined to get by with a shorter insertion, I would cut off the first part of the coupling to the point that it was difficult, but not impossible, to get the coupling started over the pipe. I might put a slight steep taper on the cut ends to eliminate burrs and to get an interference fit very soon in the insertion process. Alternatively I might search for an epoxy cement to use instead of CPVC cement. I would expect that to fill a slight gap. Is either of these better than using your existing valve? I doubt it. Isn't the water in that section of pipe somewhat cooled by the time it hits your valve? The water had to be cooler than what the thermostat was set for. Then the water lost a bit of heat on its way back to the water heater.
 

RogerED

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You need L-N divided by 2 for the insertion depth for a "perfect" joint. Depending on the application less may be adequate.
SAS, I'm sure you have resolved this by now, but for future reference: the transition fitting marked for cold water use does not have an o-ring like the hot water fittings have. The o-ring allows some movement of the pipe in the fitting to accommodate the high coefficient of expansion of plastic pipe vs. copper or other metal. Since in your application, the temperature of the water will not be fluctuating a great deal, you might be able to get by with the cold water transition fitting if your piping is not too constrained. I would be more concerned, however, if your CPVC threads were female.
 
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