I appear to to be confused about the difference between NPT threads and IPS threads. I have to put some ball valves on some old galvanized pipe and I assumed it was IPS threads. So you would get an IPS ball valve. But IPS means iron pipe straight thread and galvanized and black iron are tapered. Got myself confused. Any help appreciated.

Thanks
Peter

I think I figured it out myself IPS means iron pipe size where FIPS means female iron pipe size. Think I got the wrong imformation in the begining.

Thanks



Edited 2 times.

Glad we could help

Quote

I appear to to be confused about the difference between NPT threads and IPS threads. I have to put some ball valves on some old galvanized pipe and I assumed it was IPS threads. So you would get an IPS ball valve. But IPS means iron pipe straight thread and galvanized and black iron are tapered. Got myself confused. Any help appreciated.

Just to make it clear National Pipe Tapered Thread (NPT) is a US standard for tapered threads used on threaded pipes and fittings. NPT compatibility examples are Male NPT also known as Male Pipe Thread (MPT) and Female NPT also known as Female Pipe Thread (FPT). And an IPS is an abbreviation of Iron Pipe Straight Thread which is the Generic Name for Straight Pipe Thread (NPSH). NPT and NPS/IPS are the pipe thread standards.

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quote; And an IPS is an abbreviation of Iron Pipe Straight Thread which is the Generic Name for Straight Pipe

Here I have been using IPS for 60+ years as an abbreviation for EVERYTHING with a thread in, or on, it, and NOW you tell me that I have been wrong.

i'm curious ???
would a left handed nipple/coupling be considered IPS?
as far as i know, the thread pitch and threads per inch are the same as right handed threads, they just go the other way.
so, in the definition of IPS, does it state "turn clockwise to tighten"?

No, it would define the thread pitch and and the specifications for the cut, but not the direction, since it would be for an "infinitely narrow" part of the thread so direction would not be a factor. And as for a "straight thread", electricians are the only ones I know who use them.

I seem to recall there was a piping system that used straight threads and locknuts. You screwed the pipe into the fitting with a locknut already on the pipe, wrapped some sort of packing material between the fitting and locknut, then tightened the locknut up against the fitting. I think it was a Brit/Aussie thing. I use NPT and IPS interchangeably and have never been challenged on it, but I don't hang out with engineers.

That was a "longscrew". It was a way to insert a fitting into a galvanized drain line, similar to the sisson joint in cast iron.

To get very techie, I think IPS is iron pipe size, meaning the PIPE, and not bearing any actual reference to threads. NPS, NPT, etc,....those are THREADS. But the terms are thrown around rather loosely by all of us!

besides hj, packy and Methuselah, i wonder if anyone has ever actually used a sisson joint.
i believe i have used only 2.
kaypher "Y"s and kaypher "straight"s were the only joints that were legal prior to no hub clamps.
of course there were manhoff sleeves but the were more for adapting to a galvanized pipe without threading.

IPS: iron pipe size, vague as it may be straight ('running') or tapered
by informal convention it is interpreted as tapered unless otherwise stated

NPT: national pipe tapered (same thread as IPS tapered)

NPSM: national pipe straight/standard mechanical (running or straight thread)

The alternatives to a "longscrew" were the "Tucker" fittings,(tee, coupling/hub, etc.), which had a hub on top and threads on the bottom.

IPS IS EQUAL TO NPS
NPT - T IS TAPERED
NPS - S IS STRAIGHT
IRON PIPE HAS THE SAME OD
AS PVC

COPPER , CPVC , PEX HAVE THE
SAME OD .

3 TYPES OF WALL THICKNESS FOR EACH TYPE
EXCLUDING PEX .

PVC HAS LOWER HEAT TOLERANCES THAN
CPVC . YOUR WELCOME .