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 This topic has 4 replies, 4 voices, and was last updated 22 years, 2 months ago by Frank Hiebert.

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23 Jan 2001 at 7:59 pm #274482MasterPlumbersKeymaster
what is the formula or
equation for
solving static presure?
question: what is the static
pressure for a tank 10′ 2′ ?thanks
[email protected] 
23 Jan 2001 at 9:08 pm #289825SylvanLMPParticipant
quote:
Originally posted by [email protected]:
:confused:what is the formula or
equation for
solving static presure?
question: what is the static
pressure for a tank 10′ 2′ ?thanks
[email protected]
.433 TIMES the Height
[Edited by SylvanLMP on 23 January 2001] 
23 Jan 2001 at 9:33 pm #289826SylvanLMPParticipant
I’m Sorry I couldn’t go into more detail as my phone rang.
OK let me try to explain in a little more detail
To find the hydrostatic pressure (no flow) you take the height times . 433 in this case 10 feet.
To PROVE you take the answer in again in this case 4.33 and times that by 2.31 = 10. FT correct so far? (try it)
Now normally this question is compounded when asked of the 1st year apprentices with the following.
How much does this water weight and how many gallons are in this tank?
Well, we know if it in feet we figure 7.48 gallons in a cubic foot weighing in around 62.38 pounds.
If these measurements were in inches we would divide by 2.31 as there are 2.31 inches in a gallon Weighing in around 8.33 pounds.
So we take 2×2 = 4 10 = 40 CU. ft would equal 299.2 gallons 8.33 =2,492 POUNDS not including the weight of the tank
This question is asked when figuring roof tank installations when taking into consideration the bearing load.
Now there is another question that makes this slightly more complicated and that is if the question asks what is the “FORCE” of this water on the base fitting?
For this answer you find all the following above for the hydrostatic pressure PLUS the total weight being transferred DOWN on the lowest section.
If you have any questions please E mail me Or contact Frank as he is one of the most Knowledgeable apprentices I have met on line in a very long time.
And here you thought us plumbers only had pretty faces LOL
Good Luck
[Edited by SylvanLMP on 23 January 2001] 
24 Jan 2001 at 5:45 am #289827fourth yearParticipant
Math may not be one of your strong points. If the tank is 2′ diameter by 10 feet deep, then the volume is 1x1x3.1416×10 which equals about 31.416 cu. ft. and if I read your answer correctly, you said there are 2.31 inches in a gallon weighing 8.22 pounds. My gallon milk bottle have a lot more than 2.31 cu. in. in them.

24 Jan 2001 at 7:55 am #289828Frank HiebertParticipant
First of all it must be stated that pressure is force restricted to a unit area. The formula is Pressure = density height. It makes no difference how much volume of water you have in your tank, whether it be rectangular or cylindrical. What we are concerned with is the height and density of the medium, which I am assuming is water. 1 ft water column produces .434 psi(pounds per square inch). By simply multiplying .434 psi 10 ft we get a pressure of 4.34 lbs/square inch. Thus the pressure exerted at the bottom of your tank is 4.34 pounds per square inch. If it was a million gallon tank with a height of 10 feet the answere would still be the same. Force however is defined as a simple push, pull or weight. Force = Area pressure. So if your tank is cylindrical the area on the bottom would be 3.14 times the radius squared = 3.14 square feet, or about 452 square inches. So then Force = 452 square inches 4.34 lbs/square inch which gives a force of aproximatly 1,962.5 lbs. exerted on the bottom of the tank by the water. Don’t confuse force and pressure with weight. If it is simply weight you are looking for, the capacity of your cylindrical tank would be 31.4 cubic feet. One cubic feet of water weighs 62.5 lbs thus you can hold 1,962.5 lbs of water in your tank. Notice how the weight and force are the same here, they aren’t always, it depends on the shape of the container….. thats why I showed you . Hope somewhere in here you find the answere you were looking for. Keep in mind these numbers have been rounded off a little and I am basing these calculations at standard temperature and pressure.
Frank Hiebert
3rd yr apprentice
Edmonton, Alberta
Now a little note for 4th year;Are you not becoming the biggest hypocrite that walked the face of the earth, based on what you have been calling us, and complaining about? Are you answereing the questions and not attacking the posts of other plumbers on this board? Doesn’t seem like it to me my friend. Instead you attack Sylvan for every little typo he makes knowing full well that he is far more knowledgable in this field than ten of you and I both put together!! You would be amazed at what you can learn. I have never been maliciously critical of anyone elses responses on this board until now….but you Mr fourth year have pissed me off with your last few remarks about me in other posts. The next time you have something to say to me I would appreciate it if you would email me privately. I would do the same but it appears your email is not available eh? Probably don’t want any feedback from some of the unfortunate peaple who have taken some of your your irresponsible advice (in fairness not all your posts are bad), however some are so far out in left field I can’t help but wonder where, and if you even went to school. Just how damned long have you been a fourth year apprentice anyway? Judging by some of your responses I find it hard to believe that you got through your second year. What the hell have they been teaching you?Nevermind I’m really not that interested. In fact this is the last time I wish to discuss it, unless of course YOU decide to continue babbling about me in a public forum. Thats all I have to say.


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