Re: Water pipe size


PipeDown wrote:
> "Chris Lewis" <clewis@xxxxxxxxxxxxxxxxxx> wrote in message
> news:11evumdggls9j8a@xxxxxxxxxxxxxxxxxxxxx
> > According to PipeDown <nowhere@xxxxxxxxxxxxx>:
> >> > 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

.

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