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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....
 

Twowaxhack

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1/8 ID x 1/4 OD
1/4 ID x 3/8 OD
3/8 ID x 1/2 OD
1/2 ID x 5/8 OD
3/4 ID x 7/8 OD
 

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.
 
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