|
Posted by Don Young on August 2, 2005, 10:31 pm
No, you can't increase the pressure of a water column by reducing the pipe
size anywhere in any direction. A 10 foot high cone with point at the bottom
develops exactly the same pressure at the bottom as a 10 foot high cylinder.
Also water pressure is exactly the same in a sideways direction as downward
at any given point. Any increase in force (pounds) can only occur with a
corresponding increase in area (square inches) so the pressure (pounds per
square inch) is constant. I am not sure but I think that is known as
"Pascal's Law".
Don Young
>
>>
>> PipeDown wrote:
>>> >> > Going from small to big won't cause much of a problem, aside from a
>>> >> > "if
>>> >> > you draw too much from one faucet, you might suck air in another"
>>> >> > factor.
>>> >
>>> >> You would never suck air into a fixture unless for some very unusual
>>> >> reason
>>> >> you were pumping warter out of another fixture at a rate greater than
>>> >> the
>>> >> source can replenish it. Excessive flow at one fixture would cause a
>>> >> reduced flow at all other fixtures on the branch since all are
>>> >> passively
>>> >> powered by available water pressure. Only if a fixture were actively
>>> >> accelerating the water would a negative pressure develop in the pipe
>>> >> to
>>> >> cause air sucking.
>>> >
>>> > Heh, no, sorry.
>>> >
>>> > Take a two story house with heavily restricted water feed. Turn on a
>>> > faucet
>>> > upstairs. Now, go turn on another faucet on downstairs.
>>> >
>>> > Do you hear the faucet upstairs sucking air?
>>> >
>>> > We do ;-)
>>> > --
>>> > Chris Lewis, Una confibula non set est
>>> > It's not just anyone who gets a Starship Cruiser class named after
>>> > them.
>>>
>>>
>>> Briefly said, gravity would be that additional accelerating factor.
>>>
>>> Perhaps I was being narrow sighted since I am in a single story house
>>> but
>>> for that to happen the weight of the water column in vertical pipe
>>> leading
>>> upstairs would need to exceed the static water pressure minus that
>>> pressure
>>> relieved by the open downstairs fixture. In which case the 1/2" pipe
>>> would
>>> be advised due to the reduced weight of the water column. Such a
>>> situation
>>> should only occur in an installation flawed by inadequate water pressure
>>> or
>>> too large pipes for a given pressure/flow. I can also see that a
>>> reducing
>>> fitting an just the wrong spot on a vertical pipe could have unexpected
>>> consequences by changing the static water pressure at that point (a
>>> problem
>>> which should not happen in a horizontal run because there is no pressure
>>> gradient under static conditions)
>>>
>>> Your reply may have been essentially correct but it sure was confusing.
>>> I'm
>>> not arguing, just trying to understand completely. In fact I am still
>>> looking for a way to calculate the head pressure for each of the two
>>> cases
>>> of 10' vertical pipe 1/2" and 3/4" . While it is obvious that water in
>>> a
>>> 3/4" pipe weighs more, the difference in area (of the pipe diameter)
>>> would
>>> yeild different PSI measurements which might be closer (i.e. mass is
>>> distributed over a larger area in the 3/4" pipe). Maybe I'll post later
>>> if
>>> I can puzzle it out to my satisfaction, dosen't seem hard just short on
>>> time
>>> and willpower now.
>>
>> No, a column of water 10 ft high will produce about 4.3 psi whether
>> that column is 1/2" or 5'. Seems counter intuitive but them is the
>> facts as I was taught in my last physics class ummmmm years ago ;).
>> Total weight of water depends on column size but the pressure per sq
>> inch doesn't change.
>>
>> Harry K
>>
>
> Thats what I thought but a reducing union at the bottom would increase the
> PSI by reducing the area while keeping the water column the same weight. A
> reducing Tee would be OK as long as the size does not change in the
> vertical direction
>
| 
Yahoo! 
Google 
Windows Live 
del.icio.us 
digg 
Netscape 
XML Sitemap