Thanks: 0
Likes: 0
Needs Pictures: 0
Picture(s) thanks: 0
Results 1 to 9 of 9
Thread: Pipe measurements
-
10th March 2011, 11:25 PM #1Senior Member
- Join Date
- Jun 2008
- Location
- perth
- Age
- 79
- Posts
- 144
Pipe measurements
This is not quite a woodwork question but it has a lot to do with my shed. It's a question about pipes.
We have reticulation pipes running through our garden. Much of it is 25mm which is marked on it in black engraving. OK, so if you measure the outside dia with a vernier gauge it's nothing like 25mm. Similarly the inside dia is not 25mm either.
I've Googled for the answer, but the sites aren't helpful and I've no plumbing knowledge at all.
I had a problem with ordering some fittings. The problem's gone now but I want to take an educated approach next time. Can a member help please?
-
10th March 2011 11:25 PM # ADSGoogle Adsense Advertisement
- Join Date
- Always
- Location
- Advertising world
- Age
- 2010
- Posts
- Many
-
10th March 2011, 11:57 PM #2Senior Member
- Join Date
- Sep 2007
- Location
- Country West Oz
- Age
- 77
- Posts
- 201
I think the inside diameter is a nominal 25mm (1 inch)
That means it is not really 25mm
Hope that is confusing enough. (I don't know that this is correct, just my guess)Regards
Bradford
-
11th March 2011, 12:36 AM #3
Pipe sizes are a nightmare. NOMINAL size is typically the equivalent size of a smooth-bore (imaginary) pipe for calculating flow characteristics, with friction absent. No such thing, of course.
To make matters worse, metric conversions are sometimes "soft," not exact. And pvc pipe is typically the same dimensions of iron pipe, even though their friction values are different.
A nominal 25mm pipe would be nominal 1" (I think). OD and ID are 1.315" and 1.049" respectively. Exact conversion to metric would be 33.4mm and 26.6mm. If your measurements are close to those, Bob's your uncle; if not, best consult a plumbing supplier, because I'm in deep water here.
The foregoing is for Standard Weight (Schedule 40). For Extra Strong and Double Extra Strong, the OD's stay the same, but the ID's are smaller (thicker walls), calculations be damned.
The discrepancy between equivalent and actual diminishes in very large pipes, because the skin friction is a smaller component of calculations. At 12" Standard Weight, it vanishes. At very small sizes, skin friction dominates, and the nominal size seems to be created out of thin air.
Cheers,
JoeOf course truth is stranger than fiction.
Fiction has to make sense. - Mark Twain
-
11th March 2011, 02:57 AM #4
Kevin,
if it's black poly pipe (smooth, black, slippery stuff with screw together fittings) then there's a few different grades with different fittings.
Pressure poly is typically black with a blue stripe, or sometimes blue, but the older stuff was all black. It has a fairly thick wall and can withstand mains pressures. It uses compression poly fittings with a couple of sections which sit over the pipe.
Rural grade poly is now usually sold with a green stripe, but again, the older stuff was just plain black. It has a much thinner wall than the pressure poly. It has similar fittings to the pressure poly but there is a piece that fits inside the pipe to support it and to prevent the compression ring from crushing the pipe. It won't withstand mains pressure, at least not for long.
There is a third grade of poly which is used for garden irrigation systems which is thinner again. It's usually joined with black poly fittings which slip inside the pipe and are held in place with either metal hose clamps or plastic clips or clamps. This third system is very thin wall and is usually attached to a garden tap. Because it has a number of outlets and is usually set up so it can't be pressurised (ie, the outlets are always open) it doesn't need to be able to withstand high pressure.
Hope this helps.
BTW, there is a black pipe used inside houses now which is PEX. It's high pressure and usually uses crimp on fittings although push together fittings are also used. Not usually found in gardens.
Mick"If you need a machine today and don't buy it,
tomorrow you will have paid for it and not have it."
- Henry Ford 1938
-
11th March 2011, 08:32 AM #5
-
11th March 2011, 02:00 PM #6Senior Member
- Join Date
- Jun 2008
- Location
- perth
- Age
- 79
- Posts
- 144
Thanks for your reply Bradford. I'm getting the drift of what's going onwith pipes. Small wonder that plumbers charge so much.
-
11th March 2011, 02:04 PM #7Senior Member
- Join Date
- Jun 2008
- Location
- perth
- Age
- 79
- Posts
- 144
Thanks for the time you've taken Mick. I'm getting the idea now. I wonder if plumbers and pipe-makers conspire to make things complicated the better to charge us more. Just a thought.
Thanks again Mick.
Regards,
Kevin
-
11th March 2011, 02:08 PM #8Senior Member
- Join Date
- Jun 2008
- Location
- perth
- Age
- 79
- Posts
- 144
Thanks Joe for the time you've taken. I'm getting the drift now.
I guess our nails and screws are really nominal in their dimensions too. I've tended to be cynical about plumbers and their pipes. But things are clearer now.
Again, thanks.
Regards,
Kevin
-
11th March 2011, 02:10 PM #9Senior Member
- Join Date
- Jun 2008
- Location
- perth
- Age
- 79
- Posts
- 144
Thanks Alex.
Regards,
Kevin.
Similar Threads
-
Measurements
By groeneaj in forum WOODWORK - GENERALReplies: 8Last Post: 9th September 2010, 12:00 AM -
How to add measurements
By benupton in forum DESIGN & DESIGNING / GOOGLE SKETCHUPReplies: 1Last Post: 7th March 2010, 05:34 PM -
Saw measurements.
By spokeshave in forum TABLE SAWS & COMBINATIONSReplies: 3Last Post: 25th February 2010, 09:01 PM -
American measurements
By BernieP in forum WOODWORK - GENERALReplies: 106Last Post: 6th December 2006, 03:59 AM -
American Measurements
By Dan in forum TIMBERReplies: 45Last Post: 8th April 2005, 12:19 PM