On Sun, 16 Oct 2005 22:05:01 +0000, Jen wrote:

"0tterbot" wrote in message
...

if in either case, it IS already continuous, i'd assume you have too many
outlets for the pressure you are able to get, & therefore need fewer
outlets for more pressure (but i'm not sure about this or what to do about
it).
kylie



Thanks for the help from you both.

The advice you've been given is correct.

If you have a straight run of pipe, as the water flows past each outlet
(sprinkler) some of the water goes out the sprinkler, therefore for each
sprinkler outlet on a run of pipe, there is that much less water available
for the sprinklers down the line. In an extreme situation,
theoretically, you could end up with *no* water coming out of the last
sprinkler.

The efficiency of a sprinkler system relies on having both sufficient
pressure and flow. So you need enough "force" pushing the water
(pressure), as well as sufficient litres per minute (flow) flowing through
the pipes. The first can *only* be remedied by installing a pressure pump
(or moving your house and yard to a position physically lower than it is
now :-))

Flow can be rectified by increasing the size of the pipe -- larger
diameter gives more volume,gives greater flow, or at least less loss of
flow due to friction through the pipe and fittings (tees, elbows etc).

However, the flow is limited by the size of pipe you have supplying your
house, so increasing the final run of pipe to the sprinklers, won't really
give much improvement, unless it comes off from *immediately* after the
meter.

If you are running micro-sprays or drippers, then all you can do is
"ring" the pipe so water is flowing from both directions (as has been
suggested), to do this, simply come off your tap with a tee, then lay pipe
in both directions to encircle (or en-square it if you like ;-)) the
garden, this equalises the water available to the outlets.

If you are running pop-up or gear-drive sprinklers, then the only way you
can rectify the problem, ("ringing" the pipe will help a *small* bit), is
to divide (or is it multiply?) the pipe layout in two (or maybe three or
more). By that I mean if you are currently running 6 sprinklers at
once....separate them so you run three at a time only. But.......

If you have these types of sprinklers you *need* to do a flow test to
determine how many litres/minute flow you have. (time how long it takes to
fill a 9 litre bucket, then, divide 9 litres by the seconds to fill then
multiply by 60 to give l/min -- I think...usually I just use a table on a
design form!....and you should subtract a percentage from this final
figure to allow for "shrinkage", such as others in the neighborhood using
taps at the same time...or if you live in Roma Qld....for the council to
turn the pumps on the bores down at random times so everyone's pressure
drops!!:-( )

Every sprinkler/dripper/whatever has a flow rating (which, in the case
of pop-ups and gear drives you must find out). So if you had, say, a flow
of 35 litres per minute, and your sprinklers needed 10 litres per minute
each to function....you could only run three of them at once. So if your
garden needed 5 sprinklers to cover it properly, you would then have to
install *two* separate pipes, one with 2 sprinklers on, the other with 3.

Here endeth Sprinkler design 101 :-) Sorry if I have been
teaching folks here to "suck eggs".

Charles -- Plumber, PC technician, and (currently) plumbing retail drone.
--
If some days are diamonds and some days are stone....
Then some days I live in a quarry!!