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Richard Nixon

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When is 1/2" not 1/2"? Well, always, of course, but when does it have an O.D. of 0.625"?

I have a mobile home in which the all risers look like 3/8", but measure exactly 5/8" O.D. All the fittings are labeled "1/2" and the pipe is labeled "1/2 (15mm)". I had to splice in a globe valve because a cut-off valve had failed. I bought a "1/2 x 1/2" valve at Ace and it had exactly 5/8" I.D. - fit the cut pipe perfectly.

I can't find any evidence that this size of pipe ever existed. I would write it off as 3/8 pipe, but the dimensions are not quite right and *everything* is labeled 1/2". I would write it off as some obsolete mobile home oddity, but I bought a matching, newly made globe valve quite by accident. I even went to Lowes and measured some 1/2" pipe and fittings to make sure the dimensions match the standards given everywhere for 1/2" pipe. 15 mm is doesn't even match the I.D. of 1/2" schedule 40.

My brain hurts....
 

Richard Nixon

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mobile home, probably polybutelyne.
Nope, it's PVC and CPVC, except that some of the drains are ABS and the main drain and stacks are (probably) polybutylene. I would take it for nominal 3/8 pipe except that every bit of it is labeled 1/2, and the O.D. is slightly smaller than even the standard spec for 3/8 let alone 1/2.
 

Jeff Handy

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Post some pics of the pipes and drains, there should be printed info on them which will help to identify brand and type.
 

Richard Nixon

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Post some pics of the pipes and drains, there should be printed info on them which will help to identify brand and type.
The brand is Genova. The "15mm" corresponds perfectly to the measured OD of the pipe, but I can't find where this is a real pipe OD. The cold water is PVC or CPVC, the hot water is all CPVC. I have some suspicion that this could be aftermarket work. E.G. under the house all the drains are ABS or (probably) PB but inside, it's a hodgepodge of PVC and ABS with PVC fittings. There are penetrations in the belly board sufficient to account for replacing the entire water supply system. But what I do see still appears quite old.
 

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JG plumbing

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Cpvc and pex are C.T.S.(copper tube size) on the outside diameter for good reason and have different I.D.'s. They are sdr 9.

Cts
Schedule 40
Schedule 80
SDR

These all mean different things related to I.D. and O.D.
 

Richard Nixon

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Don't PVC and CPVC have exactly the same O.D.? Coincidentally, I recently made a small structure that mixed both, and the same fittings worked for both.

I got a micrometer and the O.D. of this pipe measures exactly 0.625", both the PVC and CPVC. Which corresponds to no published pipe dimensions that I can find.

At the same hardware store where I bought the "1/2" CPVC fittings that fit this pipe perfectly, there are, on the shelf below, PVC fittings with the expected dimensions for nominal 1/2" pipe. These would /not/ fit the "1/2" PVC pipe in my house at all.

This must be some low-standard junk that was done at one time in mobile homes - why can't I find any evidence of its existence?
 

JG plumbing

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Don't PVC and CPVC have exactly the same O.D.? Coincidentally, I recently made a small structure that mixed both, and the same fittings worked for both.

I got a micrometer and the O.D. of this pipe measures exactly 0.625", both the PVC and CPVC. Which corresponds to no published pipe dimensions that I can find.

At the same hardware store where I bought the "1/2" CPVC fittings that fit this pipe perfectly, there are, on the shelf below, PVC fittings with the expected dimensions for nominal 1/2" pipe. These would /not/ fit the "1/2" PVC pipe in my house at all.

This must be some low-standard junk that was done at one time in mobile homes - why can't I find any evidence of its existence?
No. I don't know why you think they should. Cpvc is Cts. Except when you are talking schedual 40. Schedual 40 cpvc is light Grey it fits schedual 40 pvc.

.625 is 5/8". Just like copper 1/2" I.d tube.
 

Richard Nixon

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No. I don't know why you think they should. Cpvc is Cts. Except when you are talking schedual 40. Schedual 40 cpvc is light Grey it fits schedual 40 pvc.

.625 is 5/8". Just like copper 1/2" I.d tube.
Because a dozen charts on a dozen sites say PVC and CPVC are the same OD, and none I can find say otherwise. Because I just measured a piece of 1/2" CPVC at 0.840", and clearly labeled 1/2" PVC under my sink at 0.625". Only schedule 80 CPVC (and conduit) are gray (now, at least); I had to special order some recently. It matches the OD of schedule 40 PVC within 0.001".
 

JG plumbing

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I think your getting caught up in material type when you need to pay attention to size.
 

Tim Whistler

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Because a dozen charts on a dozen sites say PVC and CPVC are the same OD, and none I can find say otherwise. Because I just measured a piece of 1/2" CPVC at 0.840", and clearly labeled 1/2" PVC under my sink at 0.625". Only schedule 80 CPVC (and conduit) are gray (now, at least); I had to special order some recently. It matches the OD of schedule 40 PVC within 0.001".
CPVC and PVC tubing are not the same size. PVC has a larger O.D.
 
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