Comments on: Calculate length of a pipe from the volume it holds
http://ask.metafilter.com/59183/Calculate-length-of-a-pipe-from-the-volume-it-holds/
Comments on Ask MetaFilter post Calculate length of a pipe from the volume it holdsThu, 22 Mar 2007 07:41:24 -0800Thu, 22 Mar 2007 07:41:24 -0800en-ushttp://blogs.law.harvard.edu/tech/rss60Question: Calculate length of a pipe from the volume it holds
http://ask.metafilter.com/59183/Calculate-length-of-a-pipe-from-the-volume-it-holds
How long would a 3/4 inch inner diameter pipe need to be to hold exactly 27 gallons of water? <br /><br /> A co-worker tried to switch from his well to the county water utility. The feed from the street was run to the house several years ago but not turned on. They completed the hook up at the house, turned on the water at the street, and 27 gallons of water ran into the pipe then stopped. There's a blockage stoping the water, but rather than randomly dig up the yard, he'd like to pinpoint the blockage location by doing the math. I figured MeFi's math geniuses could lick this one easy.post:ask.metafilter.com,2007:site.59183Thu, 22 Mar 2007 07:37:19 -0800putzface_dickmanvolumeplumbingmathwaterBy: RustyBrooks
http://ask.metafilter.com/59183/Calculate-length-of-a-pipe-from-the-volume-it-holds#889795
1 gallon is 231 cubic inches. So the answer is 231 / (pi*r*r) = 10.93 feet.comment:ask.metafilter.com,2007:site.59183-889795Thu, 22 Mar 2007 07:41:24 -0800RustyBrooksBy: RustyBrooks
http://ask.metafilter.com/59183/Calculate-length-of-a-pipe-from-the-volume-it-holds#889798
Whoops, sorry, 10.93 feet is for one gallon. 27 gallons is obviously 295 feet.comment:ask.metafilter.com,2007:site.59183-889798Thu, 22 Mar 2007 07:43:28 -0800RustyBrooksBy: vacapinta
http://ask.metafilter.com/59183/Calculate-length-of-a-pipe-from-the-volume-it-holds#889800
<i>I figured MeFi's math geniuses could lick this one easy.</i><br>
<br>
Uh...its an arithmetic problem:<br>
<br>
Volume/(Cross-sectional Area of pipe) = Lengthcomment:ask.metafilter.com,2007:site.59183-889800Thu, 22 Mar 2007 07:45:20 -0800vacapintaBy: plinth
http://ask.metafilter.com/59183/Calculate-length-of-a-pipe-from-the-volume-it-holds#889801
The volume for a cylinder is πr<sup>2</sup>h or in this case 0.442h (assuming the internal radius is .375 inches - Rusty - looks like you used .75 as the radius).<br>
1 gallon is 233 cubic inches<br>
27 gallons is 6291 cubic inches.<br>
6291 = 0.442h<br>
6291/0.442 = h<br>
14233 = h<br>
which is 1186 feet. I'm thinking that it's not 3/4" pipe once it leaves the house.comment:ask.metafilter.com,2007:site.59183-889801Thu, 22 Mar 2007 07:45:56 -0800plinthBy: notsnot
http://ask.metafilter.com/59183/Calculate-length-of-a-pipe-from-the-volume-it-holds#889804
radius=1/2 of diameter, so 3/8.<br>
area=pi* rad^2=.4418 square inches. <br>
<br>
27 gal *231=6237 cubic inches.<br>
<br>
6237/.4418=14117 inches, or 1176 feet<br>
<br>
A 3/4 feed, over that distance, is going to drive your coworker nuts unless he has some sort of storage tank and pressure booster.<br>
<br>
On preview, rusty, i think there's something wrong with your calculation.comment:ask.metafilter.com,2007:site.59183-889804Thu, 22 Mar 2007 07:46:38 -0800notsnotBy: deadfather
http://ask.metafilter.com/59183/Calculate-length-of-a-pipe-from-the-volume-it-holds#889805
It's 3/4 inch <em>diameter</em>. So, (231 / (pi*r*r)) * 27 = 1,117 ftcomment:ask.metafilter.com,2007:site.59183-889805Thu, 22 Mar 2007 07:47:02 -0800deadfatherBy: deadfather
http://ask.metafilter.com/59183/Calculate-length-of-a-pipe-from-the-volume-it-holds#889806
1,177. Mistyped at the end.comment:ask.metafilter.com,2007:site.59183-889806Thu, 22 Mar 2007 07:47:29 -0800deadfatherBy: bonehead
http://ask.metafilter.com/59183/Calculate-length-of-a-pipe-from-the-volume-it-holds#889807
I get 1176.5 ft also.<br>
<br>
I don't think that the pipe diameter given is entirely correct.comment:ask.metafilter.com,2007:site.59183-889807Thu, 22 Mar 2007 07:47:38 -0800boneheadBy: DU
http://ask.metafilter.com/59183/Calculate-length-of-a-pipe-from-the-volume-it-holds#889812
I like how many different answers there are to this very simple problem. <br>
<br>
Also, if there's a blockage that is water tight it might also be air tight, in which case you could have compressed air in there (or maybe it would come back out the incoming end?) which would put the blockage farther on.comment:ask.metafilter.com,2007:site.59183-889812Thu, 22 Mar 2007 07:51:56 -0800DUBy: notsnot
http://ask.metafilter.com/59183/Calculate-length-of-a-pipe-from-the-volume-it-holds#889817
Putzface_dickman, is this out in the boonies, where such a number (roughly a quarter mile) makes sense? Referring to the uniform plumbing code, for 1000 feet, if he's got less than 45 PSI at his house (more at the main), he can't run anything at all. For 46-60 psi, again at this house, he can run a toilet, no more. Even for over 60 psi, he can only run a toilet and cold water. In that high range, a 1" line can run a small household - two toilets, a lavatory (bathroom sink) and a kitchen sink.comment:ask.metafilter.com,2007:site.59183-889817Thu, 22 Mar 2007 07:54:30 -0800notsnotBy: DU
http://ask.metafilter.com/59183/Calculate-length-of-a-pipe-from-the-volume-it-holds#889818
Also also, <a href="http://futureboy.homeip.net/frinkdocs/">frink</a>, the awesomest unit conversion tool of all time, gives the answer as 358.6 meters or 1176.5 feet.comment:ask.metafilter.com,2007:site.59183-889818Thu, 22 Mar 2007 07:55:23 -0800DUBy: putzface_dickman
http://ask.metafilter.com/59183/Calculate-length-of-a-pipe-from-the-volume-it-holds#889819
Well, his house is 600ft from the street. He must be wrong about the diameter of the pipe. Thanks to your help he'll calculate likely distances from likely pipe diameters so that he's making a more educated use of the backhoe he'll be hiring.<br>
<br>
This may be arithmetic, but I'd rather take 5 minutes and look like an idiot on Metafilter to relearn something than to take 45 minutes to relearn it on my own.comment:ask.metafilter.com,2007:site.59183-889819Thu, 22 Mar 2007 07:57:20 -0800putzface_dickmanBy: RustyBrooks
http://ask.metafilter.com/59183/Calculate-length-of-a-pipe-from-the-volume-it-holds#889820
Heh, yeah, 3/4" would be the diameter not the radius. My bad.comment:ask.metafilter.com,2007:site.59183-889820Thu, 22 Mar 2007 07:58:32 -0800RustyBrooksBy: DU
http://ask.metafilter.com/59183/Calculate-length-of-a-pipe-from-the-volume-it-holds#889825
According to my calculations and assumptions (like that air could be trapped in there, etc), I think up to 1/3 of the pipe could be filled with air. That only brings it down to 800 ft, so either I'm wrong (distinct possibility) or the data are (also easy to believe).<br>
<br>
^ Most helpful AskMe answer evercomment:ask.metafilter.com,2007:site.59183-889825Thu, 22 Mar 2007 08:02:21 -0800DUBy: DU
http://ask.metafilter.com/59183/Calculate-length-of-a-pipe-from-the-volume-it-holds#889827
OMGDUMAS: It wouldn't bring it <b>down</b> at all. It would push it up to like....1800 ft.comment:ask.metafilter.com,2007:site.59183-889827Thu, 22 Mar 2007 08:03:23 -0800DUBy: notsnot
http://ask.metafilter.com/59183/Calculate-length-of-a-pipe-from-the-volume-it-holds#889830
Another thing to consider is that the blockage might have allowed some water past it, then locked up tight after moving a ways. The best solution will be to have the county dig up the tap (at the street) and cut it off, then blow through the house end with compressed air or water - blow the blockage back through the tap end.comment:ask.metafilter.com,2007:site.59183-889830Thu, 22 Mar 2007 08:04:28 -0800notsnotBy: caddis
http://ask.metafilter.com/59183/Calculate-length-of-a-pipe-from-the-volume-it-holds#889836
Schedule 40 pipe, a likely schedule for such service, has a nominal diameter of .75 inches and an actual internal diameter of 0.824 inches.comment:ask.metafilter.com,2007:site.59183-889836Thu, 22 Mar 2007 08:10:53 -0800caddisBy: JJ86
http://ask.metafilter.com/59183/Calculate-length-of-a-pipe-from-the-volume-it-holds#889851
Math calcs aside, he shouldn't have to randomly dig up the yard. Dig up near the connection to the service valve and then cut the pipe there. Blow out the service pipe with an air compressor which whould hopefully relieve the blockage. Open the valve just to make sure that there isn't blockage on the other side and hook everything back up.comment:ask.metafilter.com,2007:site.59183-889851Thu, 22 Mar 2007 08:28:53 -0800JJ86By: gaby
http://ask.metafilter.com/59183/Calculate-length-of-a-pipe-from-the-volume-it-holds#890008
The basic maths here is:<br>
- Radius of a circle (r) = diamater / 2<br>
- Area of a cirle = πr&sup2;<br>
<br>
According to google, 1 US gallon = 231.000001 cubic inches, so 27 gallons = 231 * 27 = 6237 in&sup3;<br>
<br>
Therefore:<br>
<br>
Radius of pipe (r) = 3/8 of one inch = 0.375in<br>
Area of pipe = π x ( 0.375 x 0.375 ) = 0.441786467<br>
<br>
- volume of pipe = area x length<br>
<br>
Which we can rewrite as <br>
<br>
- volume / area = length.<br>
<br>
Put in our numbers:<br>
<br>
6237 / 0.441786467 = 14117.682 inches long, or 1176.4735 feetcomment:ask.metafilter.com,2007:site.59183-890008Thu, 22 Mar 2007 10:08:00 -0800gabyBy: tayknight
http://ask.metafilter.com/59183/Calculate-length-of-a-pipe-from-the-volume-it-holds#890030
DU: how did you get frink to figure that out?comment:ask.metafilter.com,2007:site.59183-890030Thu, 22 Mar 2007 10:18:16 -0800tayknightBy: RikiTikiTavi
http://ask.metafilter.com/59183/Calculate-length-of-a-pipe-from-the-volume-it-holds#890133
Sometimes the meter (and part of the supply?) is smaller than the actual length of the supply pipe, so you may want to assume 1":<br>
<br>
<a href="http://www.irrigationtutorials.com/sprinkler03.htm">[http://www.irrigationtutorials.com/sprinkler03.htm]</a><br>
<br>
<em>Try to find a size stamped on the meter. If you can't find a size, ask your water company or just assume the meter is the next size SMALLER than the pipe running to the house. It is common for the meter to be one size smaller than the pipe. Standard water meter sizes are: 5/8", 3/4", 1", 1 1/2".</em><br>
<br>
Perhaps you can check the house side and see if it looks like the house side supply looks larger?comment:ask.metafilter.com,2007:site.59183-890133Thu, 22 Mar 2007 11:11:39 -0800RikiTikiTaviBy: DU
http://ask.metafilter.com/59183/Calculate-length-of-a-pipe-from-the-volume-it-holds#890158
Frink one liner: 27 gallons/(pi * ((.75 inch)/2)^2) -> ft<br>
<br>
I ♥ frinkcomment:ask.metafilter.com,2007:site.59183-890158Thu, 22 Mar 2007 11:23:46 -0800DUBy: JackFlash
http://ask.metafilter.com/59183/Calculate-length-of-a-pipe-from-the-volume-it-holds#890218
Google will also calculate and do conversions for you. Just paste in:<br>
<br>
27 gallons/(pi * ((3/4 inch)/2) squared) in feetcomment:ask.metafilter.com,2007:site.59183-890218Thu, 22 Mar 2007 12:00:33 -0800JackFlashBy: Joe Invisible
http://ask.metafilter.com/59183/Calculate-length-of-a-pipe-from-the-volume-it-holds#890245
Depends on the temperature of the water.comment:ask.metafilter.com,2007:site.59183-890245Thu, 22 Mar 2007 12:17:09 -0800Joe InvisibleBy: 6550
http://ask.metafilter.com/59183/Calculate-length-of-a-pipe-from-the-volume-it-holds#890280
If caddis is correct and it's schedule 40 with an actual ID of 0.824" that comes out to 975 feet for 27 gallons.<br>
<br>
If RikiTikiTavi is right and the supply pipe is 1" (reducing to 3/4 to the meter) then the length is 662 feet.<br>
<br>
I think your friend needs more information but honestly I think he's up for quite a bit of digging.comment:ask.metafilter.com,2007:site.59183-890280Thu, 22 Mar 2007 12:48:02 -08006550By: jdfan
http://ask.metafilter.com/59183/Calculate-length-of-a-pipe-from-the-volume-it-holds#890315
Your friend needs to contact a plumber... unless he enjoys random digging in his yard. Plumbers have tools and years of training/experience (and will hire and supervise the backhoe portion).<br>
<br>
Just because 27 gallons went in doesn't mean the blockage is that far in. There's air in the system and the blockage is probably the combined distance of 27 gallons plus the now pressurized air.<br>
<br>
According to my plumber friend, 'town' water pressure is usually around 135psi (if I recall correctly) during the day and goes up/spikes at night (less demand). And most lines going from the curb to the house are 1". Or at least that's the code around these parts (Western NY).comment:ask.metafilter.com,2007:site.59183-890315Thu, 22 Mar 2007 13:19:12 -0800jdfanBy: DevilsAdvocate
http://ask.metafilter.com/59183/Calculate-length-of-a-pipe-from-the-volume-it-holds#890436
<i>Depends on the temperature of the water</i><br>
<br>
No, it doesn't. If he were asking what length of pipe would hold a given <i>mass</i> of water, it would (slightly), but that's not what he asked.comment:ask.metafilter.com,2007:site.59183-890436Thu, 22 Mar 2007 15:38:56 -0800DevilsAdvocateBy: lostburner
http://ask.metafilter.com/59183/Calculate-length-of-a-pipe-from-the-volume-it-holds#890523
Okay, algebraic gymnastics.<br>
<br>
If you do find out the actual diameter of the pipe, and all your previous assumptions are correct (no air, no leakage, etc) then here's the formula to figure out the distance with all the conversions built in and everything:<br>
<br>
Distance in feet = 661.77 divided by the square of the diameter in inches.<br>
D=661.77 / (diameter^2)<br>
<br>
This is accurate to within .01ft of the best of the above calculations (by notsnot, bonehead, DU, gaby).comment:ask.metafilter.com,2007:site.59183-890523Thu, 22 Mar 2007 17:03:32 -0800lostburnerBy: JJ86
http://ask.metafilter.com/59183/Calculate-length-of-a-pipe-from-the-volume-it-holds#890644
I think everyone is overlooking the obvious with all these precise calculations. How the hell is all the water from the blockage going to get out of a faucet? I would be impressed if you could entirely empty a pipe with a majority of the water lower than the head....<br>
<br>
That's why I get paid the big bucks as an engineer, fellas. The problem as written is insoluble unless you know the depth of the water main. I'm guessing that the problem is most likely not in his water service but is in the main.comment:ask.metafilter.com,2007:site.59183-890644Thu, 22 Mar 2007 18:56:04 -0800JJ86By: caddis
http://ask.metafilter.com/59183/Calculate-length-of-a-pipe-from-the-volume-it-holds#890654
that's a joke right jj?<br>
the problem is insoluble because the volume of water exceeds the pipe volume so the original assumption is wrong<br>
however, your head is not appreciating head, so i suggest you just go get some insteadcomment:ask.metafilter.com,2007:site.59183-890654Thu, 22 Mar 2007 19:05:48 -0800caddisBy: JJ86
http://ask.metafilter.com/59183/Calculate-length-of-a-pipe-from-the-volume-it-holds#890658
Well that too, obviously....<br>
<br>
I just think it's funny that the MeFi collective genius is barking up the wrong tree trying to equate the 27 gallons to the length of pipe.comment:ask.metafilter.com,2007:site.59183-890658Thu, 22 Mar 2007 19:11:28 -0800JJ86By: JJ86
http://ask.metafilter.com/59183/Calculate-length-of-a-pipe-from-the-volume-it-holds#890675
<a href="http://fileanchor.com/93734.jpg">Here's a little hint to help the calculators.</a>comment:ask.metafilter.com,2007:site.59183-890675Thu, 22 Mar 2007 19:32:32 -0800JJ86By: putzface_dickman
http://ask.metafilter.com/59183/Calculate-length-of-a-pipe-from-the-volume-it-holds#890846
So, the plumber surmised that the obstruction was another shutoff valve. They adjusted their assumption about the diameter of the pipe. From the calculation supplied decided that it was closer to the house than to the street. They dug from the house out a few feet, found a shutoff valve. It broke when they tried to open it, so it's being replaced today. I didn't learn what the final diameter of the pipe was, but did hear that the plumber from the water utility determined that the water pressure in the house will be 80 psi once he's connected. That's up from 60psi from the well. <br>
<br>
The curious among you could probably determine the exact distance (It's roughly 600ft) from the street to the house as well as the diameter of the pipe. <br>
<br>
Thanks for the help.comment:ask.metafilter.com,2007:site.59183-890846Fri, 23 Mar 2007 05:01:45 -0800putzface_dickman