this video was far beyond all expectations, I was just studying for giggles and was searching for the relationship between head pressure and elevation and this came up, pretty dang fantastic! Thank you!
Interesting, but in order to "go beyond the words" and understand the interpretation, it seems that the word "head" should be struck and simply refer to a 5' or 10' test stack because "head" is a measurement of pressure not height. A foot of head is is equal to. 433 psi, based on a column of water 1 foot tall by 1 square inch, as the IRC commentary in the video accurately states a 10ft head is 4.33psi. However, a based on nominal inside diameter, a 2“ pipe stack would only need to be 7.35 ft tall and a 4“ pipe would be less than 2 ft tall to generate 4.33 psi. I have never seen this considered logically. I am certain an inspector would fail the inspection and quickly pull out the code paragraph stating the test should be 10ft tall (or 5 for IRC.) Thoughts?
This is a pretty deep discussion for a youtube comment, but I'll see what I can do. What you are missing is that fluid exerts pressure in all directions (except up because of gravity). Conceptually, imagine that stack of water inside a tall one inch square tube. The fluid will be pushing outwards on the tube. Now imagine that water as one inch tall cubes stacked on top of each other. When you put a cube of water on top of another to create your head, the cube puts additional pressure on the cube below. in the downward and outward directions, that lower cube now has more pressure than the one above pushing on the tube and downward. This is how you develop the head pressure on the sides of the tube and why you need the height above the last fitting you are testing. This leads us to your comment about pipe size. Those stacked cubes of water are exerting pressure outward and that is resisted by your one inch tube (the test). Okay. Now double the size of the tube and put two one-inch columns of water cubes inside. The pressure at the sides of the cubes against the tube are resisted by the tube. But, the sides of the two one inch water stacks that face each other both exert an equal and opposite pressure toward each other. They cancel out. Now add more and more one inch columns of water in a bigger pipe. They always cancel each other except the sides touching the pipe you are testing. Here a PSI (pounds per square inch) is being placed on the sides of the pipe no matter how big the diameter. This is why the size of the pipe doesn't change the PSI generated on the sides of the pipe. No matter the pipe diameter, it must be the same height to generate the PSI at the bottom. Imagine a scuba diver and the pressure exerted on them as they go deeper. This pressure doesn't change if they are in a lake or the ocean (small pipe, big pipe), it's all about the depth they go. (head). I hope that makes sense and answers your question. Physics is cool.
This just makes too much sense. I don’t know when UPC changed but it’s been 5’ for quite a while. However we just make sure it’s at 42”(for non plumbers, this is 6” above the rim of your highest fixture which is generally the kitchen sink). I know they want to create 5 lbs of pressure but practically speaking it’s impossible to ever have this much pressure on the system. You have to have your sewer main blocked and then have each fixture blocked and then have rain fill up your vents to 10’. You’ll actually never have more than a couple of feet because the water would come out a bath or toilet. As for plumbers, 10’ head is such a pain in the ass. You have to get out a ladder and then secure the pipe somehow so the leverage of an extra 10’ of pipe doesn’t mess up your rough. This is especially difficult in the south(I’m in Texas) all our houses are slab so when our rough is inspected there’s only forms and dirt. This means you have to drive a stake in compacted kaliche or clay. This kind of goes along with what the code guys said about inspectors having a hard time inspecting. It’s just overkill.
@@GlennMathewson thanks for making it. I’m a plumber by trade but also a history buff so it was the perfect video. Though my comment was wrong. I looked in my 2015 UPC book and it said 10’ head. I’m on Austin and it’s UPC but all of the surrounding cities are IPC. We’ve always done 5’ in Austin and 10’ anywhere else so I just assumed it matched the codes. It must be a local thing
Glenn, have you obtain a copy of "RECOMMENDED MINIMUM REQUIREMENTS FOR PLUMBING" IN DWELLINGS AND SIMILAR BUILDINGS) “ by the Bureau of Standards.circa 1925??? aka BH13
Yes. That's an excellent part of my research collection. I show some parts from that book in this video about venting: ruclips.net/video/DvU_IX84rMc/видео.html
I had this test.recently. If on top floor and after height for sink fixtures and 8 foot walls you top off d.w.v. at rooftop and you are at about 9 plus??? Inspector just looks for leaks, doesn't measure.... comments?
I know inspectors that want a ladder to the top of the pipe and it filled to the brim. Then they wait and return to see if it is still full. This technique is reasonable, but sometimes give false fails due to an air bubble in the system that burps out. I think the method of looking for leaks is a pretty good method too. Probably a combination of both is best. None of this is a perfect science.
this video was far beyond all expectations, I was just studying for giggles and was searching for the relationship between head pressure and elevation and this came up, pretty dang fantastic! Thank you!
Interesting, but in order to "go beyond the words" and understand the interpretation, it seems that the word "head" should be struck and simply refer to a 5' or 10' test stack because "head" is a measurement of pressure not height. A foot of head is is equal to. 433 psi, based on a column of water 1 foot tall by 1 square inch, as the IRC commentary in the video accurately states a 10ft head is 4.33psi. However, a based on nominal inside diameter, a 2“ pipe stack would only need to be 7.35 ft tall and a 4“ pipe would be less than 2 ft tall to generate 4.33 psi. I have never seen this considered logically. I am certain an inspector would fail the inspection and quickly pull out the code paragraph stating the test should be 10ft tall (or 5 for IRC.)
Thoughts?
This is a pretty deep discussion for a youtube comment, but I'll see what I can do. What you are missing is that fluid exerts pressure in all directions (except up because of gravity). Conceptually, imagine that stack of water inside a tall one inch square tube. The fluid will be pushing outwards on the tube. Now imagine that water as one inch tall cubes stacked on top of each other. When you put a cube of water on top of another to create your head, the cube puts additional pressure on the cube below. in the downward and outward directions, that lower cube now has more pressure than the one above pushing on the tube and downward. This is how you develop the head pressure on the sides of the tube and why you need the height above the last fitting you are testing.
This leads us to your comment about pipe size. Those stacked cubes of water are exerting pressure outward and that is resisted by your one inch tube (the test). Okay. Now double the size of the tube and put two one-inch columns of water cubes inside. The pressure at the sides of the cubes against the tube are resisted by the tube.
But, the sides of the two one inch water stacks that face each other both exert an equal and opposite pressure toward each other. They cancel out. Now add more and more one inch columns of water in a bigger pipe. They always cancel each other except the sides touching the pipe you are testing. Here a PSI (pounds per square inch) is being placed on the sides of the pipe no matter how big the diameter.
This is why the size of the pipe doesn't change the PSI generated on the sides of the pipe. No matter the pipe diameter, it must be the same height to generate the PSI at the bottom.
Imagine a scuba diver and the pressure exerted on them as they go deeper. This pressure doesn't change if they are in a lake or the ocean (small pipe, big pipe), it's all about the depth they go. (head).
I hope that makes sense and answers your question. Physics is cool.
What a great collection!
This just makes too much sense. I don’t know when UPC changed but it’s been 5’ for quite a while. However we just make sure it’s at 42”(for non plumbers, this is 6” above the rim of your highest fixture which is generally the kitchen sink). I know they want to create 5 lbs of pressure but practically speaking it’s impossible to ever have this much pressure on the system. You have to have your sewer main blocked and then have each fixture blocked and then have rain fill up your vents to 10’. You’ll actually never have more than a couple of feet because the water would come out a bath or toilet. As for plumbers, 10’ head is such a pain in the ass. You have to get out a ladder and then secure the pipe somehow so the leverage of an extra 10’ of pipe doesn’t mess up your rough. This is especially difficult in the south(I’m in Texas) all our houses are slab so when our rough is inspected there’s only forms and dirt. This means you have to drive a stake in compacted kaliche or clay. This kind of goes along with what the code guys said about inspectors having a hard time inspecting. It’s just overkill.
Glad you like the video. I've got a limited audience for building code history and education! ha, ha!
@@GlennMathewson thanks for making it. I’m a plumber by trade but also a history buff so it was the perfect video. Though my comment was wrong. I looked in my 2015 UPC book and it said 10’ head. I’m on Austin and it’s UPC but all of the surrounding cities are IPC. We’ve always done 5’ in Austin and 10’ anywhere else so I just assumed it matched the codes. It must be a local thing
Glenn, have you obtain a copy of "RECOMMENDED MINIMUM REQUIREMENTS FOR PLUMBING" IN DWELLINGS AND SIMILAR BUILDINGS) “ by the Bureau of Standards.circa 1925??? aka BH13
Yes. That's an excellent part of my research collection. I show some parts from that book in this video about venting: ruclips.net/video/DvU_IX84rMc/видео.html
What is a peppermint test.
Where does the 10' head need to be? 10' from the lowest part of the main, near the test wye? Or 10' from the highest point/joint on the system?
I had this test.recently. If on top floor and after height for sink fixtures and 8 foot walls you top off d.w.v. at rooftop and you are at about 9 plus??? Inspector just looks for leaks, doesn't measure.... comments?
I know inspectors that want a ladder to the top of the pipe and it filled to the brim. Then they wait and return to see if it is still full. This technique is reasonable, but sometimes give false fails due to an air bubble in the system that burps out. I think the method of looking for leaks is a pretty good method too. Probably a combination of both is best. None of this is a perfect science.
I’d wager that is Evansville Indiana